The cytological diagnosis of paediatric renal tumours

Transcription

1 Department of Pathology, Tata Memorial Hospital, Parel, Mumbai, India Correspondene to: Dr T Shet, 309/31, Prabhudarshan, S.S. Nagar, Amboli, Andheri (W), Mumbai , India; tanujashet@ yahoo.om; tanujashet5@gmail. om Aepted 30 June 2009 Published Online First 20 August 2009 The ytologial diagnosis of paediatri renal tumours T Shet, S Viswanathan ABSTRACT Fine needle aspiration ytology (FNAC) is used for preoperative diagnosis of paediatri renal tumours, espeially in entres where preoperative hemotherapy is advoated in Wilms tumour. This review fouses on salient ytologial features in speifi paediatri renal tumours, the approah to resolving a differential diagnosis and the role of anillary methods in diagnosis of paediatri renal tumours. Cruial differential diagnoses inlude distinguishing: Wilms tumour from benign tumours in the kidney like multiysti nephroma or ongenital mesoblasti nephroma; aggressive non-wilms tumours of kidney like rhabdoid tumour of kidney; and Wilms tumour from other paediatri round ell saromas like neuroblastoma, non-hodgkin lymphoma et. An approah based on lassifying smears aording to their ellular patterns as triphasi, round ell, spindle ell or epithelioid ell type assists in lassifying paediatri renal tumours on ytology. Immunoytohemistry for WT1, ytokeratin, synaptophysin, leuoyte ommon antigen and MIC2 will aid in evaluating round ell tumours in the renal region, while WT1, bl2, vimentin and desmin will be useful for spindle ell tumours in that region. Extra material an also be evaluated for demonstration of speifi ytogeneti abnormalities in these tumours. A heklist of ommon tumours in a partiular age group, relevant linial information, awareness of distintive and overlapping ytologial features, and appropriate use of immunoytohemistry with ytogenetis go a long way in ensuring an aurate ytologial diagnosis. Used judiiously, FNAC is as effetive a tool as a ore biopsy for preoperative diagnosis of paediatri renal tumours, and with experiene a 92% auray rate an be ahieved. Fine needle aspiration ytology (FNAC) in paediatri renal masses is performed for diagnosis of tumours in patients with advaned disease before instituting preoperative hemotherapy and for doumentation of ontralateral disease/metastases/reurrene. 1 There is a ontroversy regarding the role of FNAC in the diagnosis of operable paediatri renal tumours. Both the SIOP (International Soiety of Paediatri Onology) and NWTS (National Wilms Tumour Study Group) state that a ore biopsy in a paediatri renal tumour inreases the risk of flank relapse; hene tumours biopsied are upstaged to stage III. 2 For operable renal tumours the NWTS approah relies on primary nephretomy with further therapy based on histologial evaluation of speimen, while the SIOP protool advoates a radiologial or FNAC diagnosis permitting preoperative hemotherapy first, followed by surgery, and further therapy based on stage and histology. 2 3 Reently however the UKCCSG (United Kingdom Children Caner Study Group) onfirmed that a perutaneous needle biopsy offered an My approah aurate preoperative diagnosis in 85% of Wilms tumours with minimal risk for ompliations and loal reurrene or upstaging. 4 Although paediatri renal tumours have well defined radiology, 5 10% of tumours radiologially diagnosed as Wilms tumour proved to be benign lesions 4 ; hene FNAC is used for diagnosis in entres following the SIOP protool. FNAC is inherently a simple tehnique as ompared to a ore biopsy whih requires more expertise. The auray of diagnosis in various studies on paediatri renal tumours is diffiult to extrapolate, however in a prior study at our institute an awareness of ytomorphology of the various paediatri renal tumours improved the auray rate of diagnosis from 65% to 92%. 5 STEPS IN THE CYTOLOGICAL EVALUATION OF PAEDIATRIC RENAL TUMOURS Preliminary onsiderations Clinial information. A ytopathologist evaluating an aspirate from a renal mass or abdominal mass in a hild should always onfirm the relevant linial and radiologial information before making a diagnosis. Though exeptions our, most paediatri renal tumours onform to the outlines of age given in table 1. All aspirations should preferably be performed under radiologial guidane (most ommonly ultrasound guided) for appropriate sampling. At our institute a long spinal needle (22 or 23 gauge) is usually used for guided aspiration without any untoward event. Tehnial onsiderations. Aspirations should be performed aording to the pratie for guided aspirations in a given institution. All aspirations should undergo an on-site evaluation for adequay. In our department after brief fixation, we stain the smears with 1% toluidine blue stain as this stain gives exellent nulear details. Some entres prefer a Diff Quik stain for the same purpose. On-site evaluation also assists in olleting material for anillary studies. If there is suffiient material it should be olleted for ell blok preparation to bring out the arhitetural details in haemorrhagi aspirates. The nulear hromatin in malignant round ell tumours is best appreiated in a Papaniolaou stained smear. Always ollet one or two air dried smears for the Giemsa stain as some additional valuable features an be seen in them. Anillary studies. Needle washes or material should be olleted in relevant fixatives for onventional ytogenetis, reverse transriptase PCR or eletron mirosopy. Extra smears ould be made and olleted for immunoytohemistry (ICC) or fluoresene in situ hybridisation (FISH). J Clin Pathol: first published as /jp on 20 August Downloaded from on 19 July 2018 by guest. Proteted by opyright. J Clin Pathol 2009;62: doi: /jp

2 My approah Table 1 Age distribution of renal tumours in hildren Age group range Renal tumours to be expeted,1 year Congenital mesoblasti nephroma Wilms tumour Rhabdoid tumour 1 4 years Wilms tumour Rhabdoid tumour of kidney Clear ell saroma.4 5 years Wilms tumour.5 10 years Wilms tumour Clear ell saroma Renal ell arinoma years Renal ell arinoma Primitive neuroetodermal tumour/ewing saroma Cytologial parameters to be analysed A ytopathologist should note the following ytologial parameters while evaluating an aspirate from a paediatri renal tumour. Bakground. Features to wath for are presene of a neurofibrillary matrix in neuroblastoma, metahromati matrix in lear ell saroma of kidney (CCSK), and lymphoglandular bodies in non-hodgkin lymphoma. Cohesiveness of ells. The most disohesive paediatri renal tumour is non-hodgkin lymphoma, followed by neuroblastoma, primitive neuroetodermal tumour/ewing saroma (PNET/ES) and blastemal dominant Wilms tumour. Arrangement. Features to be observed inlude rosettes in Wilms tumour/pnet; aini or tubules, papillary fronds and intraytoplasmi globules in renal ell arinoma, et. Arborising vasulature is seen in CCSK, while in renal ell arinoma (RCC) transgressing vasulature is seen. Cytoplasmi details. A lear vauolated ytoplasm is observed in PNET/ES or CCSK, while blastemal ells in Wilms tumour lak a disernible ytoplasm. Nulei. While grooved nulei are pointers towards a CCSK, prominent nuleoli indiate a rhabdoid tumour of kidney (RTK) and lak of nuleoli favour a blastemal Wilms tumour. If a smear shows variable presene of nuleoli among the ells, a neuroblastoma should be onsidered. Chromatin pattern. Coarse nulear hromatin indiates a round ell tumour like neuroblastoma or embryonal rhabdomyosaroma. Paler finely dispersed hromatin in a round ell tumour hints at a blastemal Wilms tumour or PNET/ES. Cytologial pattern analysis based on ellular subtype. The ellular patterns in an aspirate an effetively be divided as triphasi population, round ell pattern, spindle ell and epithelioid ell pattern. Figure 1 summarises the diagnosis in paediatri renal tumour based on this approah. Cytologial features in speifi paediatri renal tumours Wilms tumour Just as on histology, all three omponents blastema, epithelium and mesenhyme are seen in aspirates from a triphasi Wilms tumour. In our experiene 5 and that of others 6 the blastema is more often represented in an aspirate even if a tumour is lassially triphasi due to the relative looser ohesiveness of this element ompared with the other two elements. The blastemal omponent forms loose lusters or sheets of widely dispersed malignant small round ells twie the size of a lymphoyte in a Giemsa stain, with an insignifiant amount of deep blue ill defined ytoplasm. 7 The nulei are round with finely dispersed nulear hromatin (fig 2A). The epithelial omponent shows tightly ohesive ells with a fair degree of ytoplasm forming small ords or aini (fig 2B). Most often the so alled rosettes in Wilms tumour are transversely ut tubules rather than true rosettes. The immature glomeruli are seen as tight three-dimensional lusters or resents with a well defined semi lunar basal lamina (fig 2B). The mesenhymal J Clin Pathol: first published as /jp on 20 August Downloaded from on 19 July 2018 by guest. Proteted by opyright. Figure 1 A flow hart depiting the approah to the diagnosis in paediatri renal tumour. CCSK, lear ell saroma of kidney; FNAC, fine needle aspiration ytology; PNET, primitive neuroetodermal tumour 962 J Clin Pathol 2009;62: doi: /jp

3 My approah Figure 2 (A) Loosely lustered blastemal ells in Wilms tumour with santy ytoplasm and round nulei with finely dispersed hromatin. Few apoptoti ells are noted (Papaniolaou, original magnifiation 6400). (B) Aspirate from a Wilms tumour reveals ords and rosette formation by the epithelial element (thin arrows) and immature glomeruli with a semi lunar refrative basal lamina (arrowheads) (Papaniolaou, original magnifiation 6400). (C) Aspirate from a triphasi Wilms tumour shows stromal fragments with entrapped glomeruli, tubules and blastema (Papaniolaou, original magnifiation 6100). (D) Wilms tumour with anaplasia on ytology shows a very large nuleus (lower half) with brisk mitosis and apoptosis (Papaniolaou, original magnifiation 6400). element is the binding omponent, and in triphasi Wilms tumour fragments of stroma with entrapped glomeruli, tubules and blastema are diagnosti (fig 2C). Variable amounts of inflammatory ells, apoptosis and nerosis may be seen. 8 The Figure 3 (A) Rhabdoid tumour of kidney, showing ells with stripped ytoplasm; the prominent nuleolus is seen in most ells (Papaniolaou, original magnifiation 6400). (B) Aspirate from a rhabdoid tumour of kidney with the typial eentrially plaed ytoplasmi inlusion (thin arrows) (Papaniolaou, original magnifiation 6400). term unfavourable ytology is used by some authors when a ombination of severe pleomorphism, very large nuleoli and atypial mitosis is seen in FNAC smears, 9 all of whih reflet anaplasia in a Wilms tumour. Patients with anaplasti Wilms J Clin Pathol: first published as /jp on 20 August Downloaded from on 19 July 2018 by guest. Proteted by opyright. J Clin Pathol 2009;62: doi: /jp

4 My approah Figure 4 (A) Smear from a lear ell saroma of kidney reveals the metahromati bakground substane with entrapped large lear polygonal ord ells in the Giemsa stain (original magnifiation 6400). (B) Aspirate from a lear ell saroma of kidney shows the grooved nulei of ords ells (thin arrow) and septal ells around blood vessels (Papaniolaou, original magnifiation 6400). tumour show resistane to hemotherapy and a redued reurrene free survival rate, even after intensive hemotherapy. 10 A diagnosis of anaplasia on ytology is made when a smear shows extremely large hyperhromati blastemal ells three times the size of the surrounding blastemal ells oupled with brisk atypial mitosis (fig 2D). A potential limitation of FNAC of Wilms tumour is the inability to extensively sample a large mass and thereby to detet anaplasia 1 and to distinguish foal from diffuse anaplasia. Rhabdomyoblasti differentiation in a Wilms tumour an assume different proportions. Most ommonly seen are the plasmaytoid rhabdomyoblasts that resemble the ganglion ells in a neuroblastoma. 5 The fetal rhabdomyomatous variant of nephroblastoma shows long rhabdomyoblasts with ross striations similar to an embryonal rhabdomyosaroma. 11 Cysti variants of Wilms tumour inlude a benign ounterpart multiysti nephroma and ysti partially differentiated nephroblastoma, whih is a well differentiated ysti Wilms tumour. Aspirates from multiysti nephroma are of low ellularity and reveal a ysti bakground with the differentiated bland orderly arranged epithelial omponent Tumours showing nuleolated epithelial ells or round ell pattern due to stripping off of the ytoplasm mimi a Wilms tumour In a ysti partially differentiated nephroblastoma, in addition to the above features, santy blastemal element may also be noted. 16 Figure 5 A primitive neuroetodermal tumour of kidney on ytology shows round ells with distint lear ytoplasm and pale nulear hromatin (Papaniolaou, original magnifiation 6400). Rhabdoid tumour of the kidney Besides an aggressive behaviour, RTKs are assoiated with CNS tumours in 13.5% of ases and hene aurate ytologial reognition is important. Aspirates from RTK show a dispersed population of small ells with foal lustering or sheets and stripped bare nulei in the bakground. RTK never has as rhabdoid an appearane as some of the other tumours with rhabdoid like phenotype, as the rhabdoid ytoplasm is fragile and easily stripped during smearing, beoming less obvious in some aspirates The presene of irregular nulei with prominent red nuleolus is often the first lue to the diagnosis. Few ells with eentrially plaed rhabdoid ytoplasm/ eosinophili ytoplasmi inlusion are always seen (fig 3). Clear ell saroma of kidney On ytology CCSK shows varying proportions of ord ells, septal ells, arborising vasulature and muopolysaharide substane. Aspirates typially reveal polygonal ord ells with eentrially plaed grooved nulei and a wispy lear ytoplasm on the bakdrop of the magenta oloured muopolysaharide ground substane (fig 4). A seond useful lue is the prominent arborising blood vessels with the septal spindleshaped ells adjaent to endothelium (fig 4B). In addition, dark ells or pyknoti degenerative apoptoti ells are also desribed. 18 CCSK also has various less ommon histologial variants whih have further deviations in their ytomorphology. 12 One known pitfall in the ytologial diagnosis of CCSK is the aspiration of normal renal tubules, simulating the immature epithelial ells of a Wilms tumour. 19 Primitive neuroetodermal tumour/ewing saroma In the last deade this tumour has been doumented with inreasing frequeny in the kidney within a wide age group from 6 to 35 years. 20 PNET/ES of kidney are linially aggressive and require hemotherapy regimens that are more intensive than a Wilms tumour. PNET/ES are frequently misdiagnosed as Wilms tumour, both being monotonous round ell tumours. PNET/ES on ytology reveals variably ohesive lusters of small round ells with irregular nulei and the typial Ewingoid or pale nulear hromatin (fig 5). Apoptoti ells, mitosis and nerosis are easily identified. The intraytoplasmi glyogen also produes a tigroid bakground in the air dried smears. Few ells always show a preserved lear vauolated ytoplasm better appreiated in the Giemsa stained smear (fig 5). J Clin Pathol: first published as /jp on 20 August Downloaded from on 19 July 2018 by guest. Proteted by opyright. 964 J Clin Pathol 2009;62: doi: /jp

5 My approah Figure 6 Aspirate from a transloation assoiated renal ell arinoma shows: (A) sheets of large ells and some papillae (Papaniolaou, original magnifiation 6100); (B) large ells with eosinophili or lear ytoplasm and intranulear inlusion (Papaniolaou, original magnifiation 6200); (C) large ell with intraytoplasmi inlusion (Papaniolaou, original magnifiation 6400); (D) ell within ell appearane (Papaniolaou, original magnifiation 6400). Renal ell arinoma Renal ell arinomas (RCC) in hildren are now reognised as a unique group of transloation assoiated arinomas. Most of them have Xp11.2 t transloations/tfe3 gene fusions with two subtypes: RCC with t(x; 17) (p11.2; q21) and RCC with t(x; 1) (p11.2; p34). As opposed to adult RCC they do not show immunoreativity to vimentin, or epithelial markers but are immunoreative to CD10 and TFE3 protein. Though indolent these neoplasms often present in advaned stages. Though earlier reports reported similar ytologial findings as in adult RCC, 12 our experiene (unpublished observations) and reports by some authors indiate that transloation assoiated RCC have unique ytomorphology. 22 Compared to adult RCC they show larger mostly polygonal, eosinophili or lear ells with an eentrially plaed nuleus with prominent nuleoli, sometimes intranulear inlusions and intraytoplasmi hyaline eosinophili inlusions. Curled up three-dimensional papillae Figure 7 Non-Hodgkin lymphoma of Burkitt subtype involving the kidney reveals dispersed ells with lymphoglandular bodies in bakground and intermediate size ells with peripheral nuleoli (Papaniolaou, original magnifiation 6400). lined by ells with lear ytoplasm, psammoma bodies and a ell in ell appearane are also noted (fig 6). Congenital mesoblasti nephroma Congenital mesoblasti nephroma (CMN) is an unommon benign spindle ell tumour of the kidney in infant hildren. The typial CMN is a hypoellular tumour just like a fibromatosis with no speifi ytogeneti aberration, while the ellular CMN is equivalent to a infantile fibrosaroma ourring in the kidney with a similar t(12;15)(p13,q25). While the former behaves in a benign fashion, some of the latter show metastases. Most of the typial CMN, being ohesive, yield non-diagnosti aspirates or ohesive lusters of bland spindle ells embedded in a fibrillary ill defined matrix with a few stripped nulei The nulei are oval to elongated, smooth in ontour, with evenly dispersed hromatin and indistint nuleoli. 24 Conversely a ellular CMN shows ellular smears with groups of and isolated spindle?ovoid ells in a neroti bakground. Tumour ells are elongated and have irregular nulei with oarse hromatin. Some ells with nuleoli and mitosis an be seen. 19 Non-Hodgkin lymphoma Renal involvement in non-hodgkin lymphoma (NHL) is usually seondary, but some ases of primary renal NHL have been desribed. 25 The ommon NHLs to involve the kidney in hildren are diffuse large B ell lymphomas or Burkitt lymphomas. The most important diagnosti lue in NHL is the presene of predominantly dispersed population of round ells with typial lymphoglandular bodies whih represent the stripped of ytoplasm of the lymphoid ells in smears (fig 7). Metanephri adenoma Though metanephri adenoma is unommon, it may our in hildren in the same age group as Wilms tumour. Essentially it shows bland immature tubules whih out of ontext an be mistaken for a Wilms tumour. However, these tubules are J Clin Pathol: first published as /jp on 20 August Downloaded from on 19 July 2018 by guest. Proteted by opyright. J Clin Pathol 2009;62: doi: /jp

6 My approah Table 2 Immunoytohemial panel in a round ell tumour in the renal region Tumour Cytokeratin WT1 MIC2 Synaptophysin LCA Blastemal WT RTK Positive (foal in 75%) Positive in most tumours 70% (nulear and ytoplasmi) evenly spaed and form tight tubules. The lining ells are monomorphi, bland, smaller, and lak mitosis as ompared to usual blastema. Rare renal tumours in hildren The spetrum of renal tumours is ever expanding and the ytopathologist an enounter any unommon tumour in the kidney. The moot point to remember is to onentrate on the aurate diagnosis of learly defined malignant tumours slotted for hemotherapy and avoid false positive diagnosis. Role of anillary methods in diagnosis of paediatri renal tumours As areas of diagnosti diffiulty do our, the ytopathologist assessing aspirates from a tumour in the renal region in hildren should take reourse to anillary methods. The following tehniques are useful in evaluating paediatri renal tumours. Immunoytohemistry ICC is the most popular method used for resolving diffiulties in ytologial diagnosis as it is very easy to obtain extra smears for ICC or to destain already stained smears without repeating the aspiration. The panel of ICC to be hosen will depend on the differentials that the pathologist has homed in on. Table 2 shows the general panel of use in round ell tumours in the renal region. The perentages given are based on our personal experiene with histologial evaluation of paediatri renal tumours (unpublished observations)/ytology 5 and some histology based studies on renal tumours The pathologist should be alerted with the expanding immunoprofile of renal tumours to use this methodology to its full potential and avoid errors. For example, the INI1 antibody immunohistohemistry, though not used on ytology to date ould be added in order to onfirm the histologial diagnosis of RTK 29 ; or WT1 has been doumented in some patients with CMN. 30 ICC helps in the following problem zones: Negative (rare ell may be positive) Negative Negative Negative Negative Negative Negative CCSK Negative Negative Negative Negative Negative PNET Negative Negative % positive Positive Negative Neuroblastoma Negative Negative or weak positive Negative Positive Negative Embryonal rhabdomyosaroma Negative Cytoplasmi staining Non-Hodgkin lymphoma Negative Negative (exept in lymphoblasti lymphoma) Table 3 Common ytogeneti alterations in paediatri renal tumours Tumour Type of abnormality Negative Negative Negative Negative (exept in lymphoblasti lymphoma) Negative Positive Wilms tumour vs other round ell tumours. A nulear and ytoplasmi staining with WT1 antigen aids in the diagnosis of Wilms tumour, 5 while a PNET/ES of kidney shows membranous staining for the MIC2 antigen and is WT1 negative. Wilms tumour vs non-wilms tumour of kidney. Cytoplasmi immunopositivity for ytokeratin will help differentiate a RTK and Wilms tumour from a CCSK while CCSK marks only with vimentin. Negativity for ytokeratin annot rule out blastemal Wilms tumour as some poorly differentiated Wilms tumours show ytokeratin negativity. The vimentin staining in CCSK is at best moderate and a strong ytoplasmi staining with vimentin atually points away from this diagnosis. 18 Differentiating within the non-wilms spetrum. CCSK marks with vimentin only, while transloation assoiated arinomas lak CK/EMA expression and express CD10. Cytokeratin will help identify RTK over other non-wilms tumours. Spindle ell tumours of kidney. The ICC panel for this group inludes WT1, bl2, vimentin and desmin. 31 WT1 is uniformly positive in the primitive undifferentiated stromal omponent in Wilms tumour and negative in the differentiated stromal elements of Wilms tumours, ellular mesoblasti nephroma (exept for rare ases), CCSK and synovial saromas. 31 Bl-2 is positive in all stromal Wilms tumours, all synovial saromas and some CCSK, but negative in CMN. 31 Eletron mirosopy Eletron mirosopy is fast losing ground to the explosion of moleular ytogenetis in the diagnosis of paediatri round ell tumours. Needle aspirates an easily be fixed in Karnosky or Universal fixative and the sediments an be proessed for examination of speifi ultrastrutural features. Eletron mirosopy is partiularly useful in identifying neuroblastoma and differentiating it from a Wilms tumour. 1 While ell proesses, Rhabdoid tumour of kidney 70% show mutation or deletion of both opies of the hsnf5/ini1 gene that map to hromosome band 22q11.2 Cellular ongenital mesoblasti nephroma t (12; 15) (p13, q25)/etv6/ntrk3 gene fusion Neuroblastoma N my amplifiation in 30 40% Primitive neuroetodermal tumour/ewing saroma t(11;22) or EWS-FLI1 is the ommonest seen in 85%; t(21;22), t(7;22), t(17;22), and t (2;22) are observed in remainder Synovial saroma 90% show t(x;18)(p11.2;q11.2) Renal ell arinoma t(x; 17) (p11.2; q21) and t(x; 1) (p11.2; p34)/xp11.2 transloations/tfe3 gene fusions J Clin Pathol: first published as /jp on 20 August Downloaded from on 19 July 2018 by guest. Proteted by opyright. 966 J Clin Pathol 2009;62: doi: /jp

7 My approah Figure 8 Smears from neuroblastoma reveals ells with variable amount of ytoplasm and bakground neuropil (arrow) (Papaniolaou, original magnifiation 6400). dense-ore granules and neurotubules are features that indiate a neuroblastoma, Wilms tumour reveals ell juntions, mirovilli, floulent basement membrane-like material, ilia and autophagolysosomes. 1 Similarly, RTK, PNET/ES and the newly desribed transloation assoiated renal ell arinomas show unique ultrastrutural features that will aid in their diagnosis. Cytogeneti evaluation of paediatri renal tumours Immunoytohemistry is not always onlusive for diagnosis of paediatri renal tumours as some of these entities even share antigeniity. 32 In suh situations unique ytogeneti features of eah tumour an help in the orret diagnosis. Table 3 presents the ommon ytogeneti findings in paediatri renal tumours FNAC material is generally of suitable quality to perform traditional ytogeneti hromosome analysis, as well as PCR based moleular tehniques. 32 Interphase FISH an also be done on fixed smears for onfirming transloation assoiated tumours. Often one pass is only required for FISH or ytogeneti studies. 35 Box 1: Cytologial differenes between Wilms tumour and neuroblastoma Wilms tumour Rosettes lak entral neuropil and usually show only one layer of ells. Bakground is lean or haemorrhagi. Minimal polymorphism unless there is skeletal musle differentiation or anaplasia. Mitoti ativity is not very brisk unless there is anaplasia. On immunoytohemistry WT1 and ytokeratin are positive. Neuroblastoma Rosettes show entral neuropil and multilayering of ells around them. The ells lining the rosettes have very santy ytoplasm. Bakground shows neuropil that entraps ells. Polymorphism in ell ytoplasm and size is observed. Mitoti ativity is very high. Immunoytohemistry reveals hromogranin or synaptophysin positivity in neuroblasti ells. Box 2: Differenes in Wilms tumour and primitive neuroetodermal tumour/ewing saroma (PNET/ES) on ytology Blastemal Wilms tumour Small ells with santy ytoplasm. Round nulei with dispersed hromatin. Blastemal ells adhere to vessels through a perivasular uff of mesenhyme. True rosettes not seen. Cells are WT1 positive, and lak synaptophysin. PNET/ES Small ells with fair amount of vauolated ytoplasm. Slightly irregular nulei with pale hromatin. Diret perivasular arrangement of the small round ells is seen. Homer Wright rosettes are noted. Cells are WT1 negative but MIC2 and synaptophysin are positive. Resolving the differential diagnosis Paediatri renal tumours should be differentiated from all round ell tumours, espeially non-hodgkin lymphoma or other tumours in the renal region in view of different management options. It is important to distinguish Wilms tumour from aggressive non-wilms tumour like CCSK, RTK and PNET/ES as the hemotherapeuti regimens in the latter are modified to suit their aggressiveness; for example, atinomyin D and a fourdrug regimen are administered in CCSK as opposed to the threedrug regimen in a Wilms tumour. Under-treating these aggressive types with usual Wilms tumour hemotherapy leads to progression and dereased survival. Wilms tumour vs neuroblastoma (ompare fig 2A and fig 8) A ommon mistake made by a ytolopathologist is interpreting a large abdominal blastemal Wilms tumour as a neuroblastoma or vie versa. 6 To add to the problem, rare intrarenal Box 3: Cytomorphologial differenes in Wilms tumour and metanephri adenoma Wilms tumour Mildly pleomorphi dispersed tumour ells with nulear overlapping, rowding and disarray. Frankly malignant nulei with irregular hromatin lumping and sometimes nuleoli. Mitosis is easily appreiated. Califiation absent in untreated ases. Tumour ells express WT1 and EMA (epithelial membrane antigen). Metanephri adenoma Monomorphi small tumour ells that are evenly spaed and form tight tubules. Bland nulei with regular ontour and indistint nuleoli. Mitosis is nearly absent. Psammomatous alifiation is noted. Tumour ells express WT1 and vimentin but are EMA negative. J Clin Pathol: first published as /jp on 20 August Downloaded from on 19 July 2018 by guest. Proteted by opyright. J Clin Pathol 2009;62: doi: /jp

8 My approah Box 4: Features that differentiate a neuroblastoma and neuroetodermal tumour/ewing saroma (PNET/ES) Neuroblastoma Tumour ells have round nulei with oarse hromatin, nuleoli are seen only in ells with ganglioni differentiation. Polymorphi populations of ells, inluding poorly differentiated ells with santy ytoplasm and ganglioni ells with eentrially plaed ytoplasm. Bakground neuropil and ganglion ells indiate obvious neuronal differentiation. Tumour ells lak MIC2 staining. PNET/ES Tumour ells have slightly irregular nulei with finely stippled hromatin; nuleoli are seen only in atypial ases. Monomorphi ell population with fair amount of vauolated ytoplasm. Obvious neuronal differentiation is absent. MIC2 is positive in most ells. neuroblastomas are desribed. 36 Overlapping ytologial features inlude presene of malignant small ells with nulear moulding and presene of rosettes in both tumours. Box 1 lists salient features that distinguish the two are. The most useful features are identifiation of neuropil entrapping the ells and the variable ytoplasm and ell sizes in ells (polymorphism) in neuroblastoma (fig 8) as against a purely blastemal Wilms tumour whih has monotonous round ells. 5 The nulei of neuroblastoma are also uniformly rounded with stippled hromatin in ontrast to those of blastemal ells whih are slightly irregular and are strongly basophili. 5 Non-Hodgkin lymphoma vs Wilms tumour (ompare fig 2A and fig 7) The ell population in NHL is extremely dispersed as ompared to a Wilms tumour and the presene of lymphoglandular bodies in the bakground assist in reognising the lymphoid nature of ells. Blastemal Wilms tumour vs PNET (ompare fig 2A and fig 5A B) Although these tumours our in patients in different age groups, exeptions may our. Box 2 provides a summary of Take-home messages Pathologists evaluating fine needle aspiration ytology from paediatri renal tumours should be aware of ruial diagnosis/ differential diagnoses that will affet management of patients; eg, non-hodgkin lymphoma vs Wilms tumour, or identify benign tumours in the kidney aurately. Classifying aspirates aording to their ellular patterns as triphasi, round ell, spindle ell or epithelioid ell types assists in lassifying paediatri renal tumours on ytology. Immunoytohemistry for WT1, ytokeratin, synaptophysin, leuoyte ommon antigen and MIC2 will aid in evaluating round ell tumours in the renal region, while WT1, bl2, vimentin and desmin will be useful for spindle ell tumours in that region. Awareness of ytologial findings in different subtypes of paediatri renal tumours helps in improving auray of diagnosis. distinguishing ytologial features. In some aademi entres, detetion of speifi transloation will help in linhing the diagnosis, espeially in ases of PNET with atypial nulear features. Wilms tumour vs CCSK (ompare fig 2A and fig 4A B) The ells in a CCSK often get stripped off with numerous bare nulei resembling a round ell tumour like Wilms tumour. 18 Blastemal ells of Wilms tumour differ from the ord ells of CCSK in having santy ytoplasm, and a omparatively hyperhromati nuleus whih laks nulear grooves. The Giemsa stain will reveal the typial muopolysaharide ground substane in a CCSK and help in ruling out a Wilms tumour. Wilms with rhabdomyoblasti differentiation vs embryonal rhabdomyosaroma Cytologial features from a genitourinary trat embryonal rhabdomyosaroma (ERMS) show more pleomorphi ells than a Wilms tumour, and nulei have muh more oarser hromatin as ompared to the differentiated rhabdomyoblasts in a Wilms tumour. 11 On ICC, ytokeratin helps to pik out small groups of disohesive epithelial ells in Wilms tumour. Wilms tumour vs metanephri adenoma Given the wide age range in a metanephri adenoma, this is a rare but ruial differential for a Wilms tumour. Metanephri adenoma, being benign, requires exision only, while Wilms tumour requires hemotherapy depending on the stage. Box 3 summarises the differenes in the two tumours. PNET/ES kidney vs neuroblastoma (ompare fig 5 with fig 8) The management and hemotherapy for a PNET/ES is very different to that for a neuroblastoma. Besides the features listed in box 4, finding of the speifi transloation will help in diagnosing a PNET/ES. Paediatri spindle ell tumours in kidney This group inludes entities like CMN, mesenhymal predominant Wilms tumour, fetal rhabdomyomatous Wilms tumour, embryonal rhabdomyosaroma of urinary trat, spindle ell variant CCSK, stromal tumours of kidney and synovial saroma. The ruial differential in this situation is to distinguish a mesenhymal predominant Wilms tumour (a malignant tumour) from the benign ongenital mesoblasti nephroma (CMN). Aspirates from mesenhymal dominant Wilms tumour are more ellular ompared to those of CMN. 12 It is highly unusual to enounter a purely stromal Wilms tumour in untreated ases and hene a areful searh for the santy blastemal omponent avoids misdiagnosis. 12 Cells in CMN are also more ohesive than the loose mesenhymal ells in a Wilms tumour. 19 Features that suggest a spindle ell variant of CCSK over a mesenhymal predominant Wilms tumour are the typial magenta ground substane, perivasular arrangement of tumour ells, and the fat that the ells of CCSK are larger and ohesive with abundant ytoplasm. 12 Summary points to be remembered while evaluating the aspirates from a paediatri renal tumour Rule out other abdominal tumours, espeially neuroblastoma. 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9 My approah Rule out a lymphoma or haematolymphoid malignany as these would be treated with non-surgial mode of hemotherapy only. Deide benign vs malignant renal tumour. Most benign tumours suh as ongenital mesoblasti nephroma or multiysti nephroma will be treated primarily with surgial exision however huge they are at presentation, while a large Wilms tumour will require preoperative hemotherapy. Subtype the malignant paediatri renal tumour as Wilms tumour vs non-wilms tumour (CCSK/RTK/PNET). CONCLUSION Paediatri renal tumours present a unique spetrum very muh amenable to an aurate ytologial diagnosis with a little bit of experiene. A heklist of ommon tumours in a partiular age group, relevant linial information, awareness of distintive and overlapping ytologial features, and appropriate use of immunoytohemistry with ytogenetis all ombine in ensuring an aurate ytologial diagnosis. Aknowledgements: We are grateful to Dr Brijesh Arora for his linial inputs and Dr Ruta Goregaonkar for immunohistohemial findings in paediatri renal tumours Competing interests: None. Provenane and peer review: Commissioned; externally peer reviewed. REFERENCES 1. Ellison DA, Silverman JF, Strausbauh PH, et al. Role of immunoytohemistry, eletron mirosopy, and DNA analysis in fine-needle aspiration biopsy diagnosis of Wilms tumour. Diagn Cytopathol 1996;14: Gommersall LM, Arya M, Mushtaq I, et al. Current hallenges in Wilms tumour management. Nat Clin Prat Onol 2005;2: Vujani GM, Sandstedt B, Harms D, et al, on behalf of the SIOP Nephroblastoma Sientifi Committee. Revised International Soiety of Paediatri Onology (SIOP) working lassifiation of renal tumours of hildhood. Med Pediatr Onol 2002;38: Vujanić GM, Kelsey A, Mithell C, et al. The role of biopsy in the diagnosis of renal tumors of hildhood: results of the UKCCSG Wilms tumor study 3. 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