Testicular tumours: What s new and what s

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1 USCAP Vancouver 2012 Testicular tumours: What s new and what s relevant? Dan Berney Introduction The rarity and complexity of testicular tumours results in unique challenges for pathologists. The difficulty in conducting randomised trials in this area, even in the commoner germ cell tumours, means that progress is slow and it is difficult to accumulate evidence for the relevance of histopathological risk factors. However a number of recent trials and retrospective analyses have suggested that some histopathological features suggestive of recurrence are more important than others. This has implications both in how we examine testicular tumours macroscopically and also microscopically. As testicular tumours encompass such a bewildering array of types, correct diagnosis of the tumour remains an overriding concern, and common pitfalls for typing will be discussed as well as advances in immunochemistry which may assist in this. Changes in treatment strategies may also have implications for the future, and I will finish by

2 examining the recent changes and how these might impact pathological investigation. The pathogenesis of germ cell tumours is a fascinating field, which may be thought to be of limited relevance to a histopathologist. However an understanding of the putative cells of origin of these tumours casts a light on their behaviour and treatment and assists in the development of future possible classifications. Staging and its relevance The current TNM classification for testicular tumour is given in Table 1.[1] In Western countries most testicular cancers are localised at presentation: meaning they qualify as Stage 1. This is further refined by the level of serum markers. When considering germ cell tumours, any tumour that is higher than stage 1 needs some form of adjuvant treatment. The challenge for histopathologists is that the choices are more difficult for the clinician in localised tumours. Many tumours are cured by orchiectomy alone. Identification of those tumours which require no further therapy is of great clinical benefit to the patient, as well as identification of those at high risk of relapse when early chemotherapy or radiotherapy can be instituted. Prognostic factors: What s relevant? The huge success of multimodal therapy including surgery and chemo-radiation for testicular germ cell tumours has made the discovery of new prognostic factors very challenging. Large cohorts of low risk patients need to be followed up with long term results to achieve statistically significant results. Below is a brief overview of important prognostic factors for localised germ cell tumours. Seminoma

3 The current literature has suggested certain prognostic factors may be more important than other established pathological criteria. Clinical stage I seminoma has an excellent prognosis and relapse rates and mortality rates are lower than those with stage I NSGCTs. However, there have been a few reports on disease relapse on men with stage I seminomas.[2-4] Interestingly, recent prognostic factors for seminoma are not included in any current staging system; these are Size of the primary tumour Nearly 20 years ago a Danish surveillance study in 261 men with stage I seminoma, showed that tumour size predicted relapse.[3] Other groups have similar findings; Warde et al. identified size of primary tumour > 4 cm and rete testis invasion as significant prognostic factors for relapse in men with stage I seminoma managed with surveillance [4] and Parker et al. found that the risk of relapse was associated with tumour size >6 cm, rete testis invasion, and lymphatic or vascular invasion as well as tumour infiltrating lymphocytes.[2] Rete testis invasion Involvement of the rete testis has been reported to present as either discontinuous pagetoid spread of seminoma within tubules [5] or as inter-tubular spread within the parenchyma.[6] It is hypothesised that parenchymal infiltration of tumour is more significant as it represents not only true invasion of the rete but also physically greater primary tumour volume.[7] At the moment, it should be correct practise to identify rete invasion and to sub-classify it. Choo et al. more recently showed that the presence of rete testis invasion was a statistically significant predictive factor for disease relapse (hazard ratio 3.5, p=0.03).[8] Compared with NSGCTs there are fewer helpful prognostic factors.

4 Vascular invasion Vascular invasion does not appear to be particularly helpful in predicting relapse in most series. Seminoma cells, particularly if poorly fixed easily smear across embedded blocks. It is very unusual to see seminoma cells associated with thrombus and attached to the vessel wall, as is commonly seen in embryonal carcinoma. Cells seen in vessels may be true vascular invasion, but it is difficult to be certain. The case for vascular invasion in seminoma as an important prognostic factor is therefore unproven, even in expert hands. Tumour size and rete testis invasion appear to be the most helpful factors to guide clinicians on further management. Non-Seminomatous germ cell tumours (NSGCTs) Unlike seminomas, lymphovascular invasion is the most powerful prognostic factor for stage I NSGCT. Fossa et al. showed in a study of 102 men with stage I NSGCT that lymphovascular invasion was the most significant risk factor predicting relapse (p=0.0007) and in a separate study, lymphovascular invasion was also identified as a significant poor prognostic factor, where 62% of men with lymphatic invasion developed distant metastases.[9, 10] This is further confirmed by Colls et al. where they demonstrated that 46% of men with vascular lymphatic invasion in their primary tumor experienced relapse.[11] In an evaluation of 88 stage I NSGCTs, multivariate analysis of these samples showed that 23 of 88 patients with vascular invasion of the primary tumor had a high risk of relapse (61%, 95% CI 55-67%) and in a linked cohort showed that surveillance of 105

5 men with stage I NSGCTs revealed that 27/105 (25.7%) men had disease relapse.[12] All relapses in this group of men occurred within two years of orchiectomy and vascular invasion was identified as one of the significant predictors of relapse during surveillance. Further, in examining the records of 82 patients with stage I NSGCTs following radical orchiectomy, 30 of 82 patients did not have vascular invasion in their primary tumor, whereas 52 of 82 men had vascular invasion.[13] In the group of men who had vascular invasion, 24 of 52 (46%) experienced relapse, thus indicating that vessel invasion could be used as a prognostic factor in monitoring stage I NSGCTs. The percentage and volume of embryonal carcinoma is another prognostic factor associated with the rate of relapse in stage I NSGCTs. In a study of 132 patients the presence of lymphovascular invasion, embryonal carcinoma and yolk sac tumour were risk factors for relapse.[14] Another study showed that 25/85 men who had predominantly embryonal carcinoma histology relapsed (p=0.008).[15] Ninety-three men with stage I NSGCTs who were placed in a surveillance study following orchiectomy, 81 men who had predominantly embryonal carcinoma component in their primary tumor and a third developed metastases, whereas none of the men without an embryonal carcinoma feature developed metastases (p=0.05).[10] A surveillance study in 373 men with stage I NSGCT [16] suggested that undifferentiated cells and the absence of yolk sac elements in the primary tumour were able to identify men with a high risk of relapse. Other groups have also identified different histopathologic adverse prognostic predictors of relapse for stage I NSGCTs. These include spermatic cord involvement (T3 disease)[17] and scrotal invasion (T4).[15] These features are present in the

6 staging system, but it is surprising how few studies have validated the T3/T4 disease classification. Current and future staging of germ cell tumours Contemporary pathological staging of testicular tumours is assessed by lymphovascular invasion, spermatic cord involvement and infiltration into the tunica vaginalis or worse, scrotum.[1] The current (2010) TNM classification, which remained unchanged between the 6 th and 7 th edition, fails to take into account the histologically identifiable parameters that have been noted above to have a bearing on prognosis and possibly affect treatment modalities. The failure to differentiate seminoma from NSGCTs (or combined tumours) in staging criteria now seems outdated. These deficiencies ought to be addressed in subsequent editions of TNM with the inclusion of rete testis invasion and tumour size assessments, as well as the exclusion of vascular invasion as a prognostic criterion in seminomas. This may lead to significant changes in treatment: for example the identification of vascular invasion in a seminoma could lead inexperienced clinicians to perform unnecessary adjuvant treatment.[18] Macroscopic and microscopic staging: Whats relevant? I suggest that currently recommended methods of macroscopic assessment may not be necessary and may in some circumstances be deleterious. The staging of testicular tumours is assessed by lymphovascular invasion, spermatic cord involvement and infiltration into the tunica vaginalis or scrotum. As suggested above, neither rete

7 testis invasion nor tumour size is accounted for in the staging system but both are probably more relevant as prognostic criteria. Vascular invasion appears only important in NSGCTs. Personal experience suggests that clinicians tend to ignore vascular invasion in seminomas in their assessments of the need for adjuvant therapy. A widely quoted paper suggests that the cord margin be taken before incising the main tumour to avoid contamination problems at the cord margin.[19] This appears in many national protocols. However this leads to a number of issues. Firstly, it does not solve the problem of contamination of the testicular parenchyma itself by loose seminoma cells once the testis is incised. This is probably equally if not more culpable as the cord margin contamination in leading to overstaging. Secondly, it runs the risk that the testis may be poorly fixed and compromise typing of the tumour, if there is a delay between orchiectomy and full macroscopy. Tumour typing remains the most important part of any testicular tumour assessment. Anything that may compromise this should be discontinued. Therefore I advise the surgeons in my institution to bivalve the testis as soon as it has been removed and to place in formalin to ensure good fixation of tissues. I suggest that if there is any chance of a testis remaining not opened for over a few hours, then this should be adopted as standard practice. Involvement of the rete testis has been reported to present as either discontinuous pagetoid spread of seminoma within tubules or as inter-tubular spread within the parenchyma. Parenchymal infiltration of tumour is more significant as it represents true invasion of the rete. Pagetoid spread may be secondary to IGCNU. These should be distinguished in any report. Involvement of spermatic cord structures by tumour may manifest in two ways. The first is by direct invasion of primary tumour which would result in a higher stage

8 (pt3). The second pattern of cord involvement results from vascular invasion with plugging of vessels and later spread into the cord soft tissues. Most authors regard only the direct stromal cord invasion as indicative of pt3 staging. However, there is considerable doubt as to where the epididymis and testicular appendages stop and the cord starts: at what level of the cord should we start to classify the tumour as T3? As suggested above, the designation of T3 has not proved the most important factor clinically: therefore, it is probably irrelevant unless more carefully defined. Challenging entities and differential diagnoses: what s relevant? As suggested above, accurate tumour typing is of prime importance for the correct treatment of testicular tumours. Below are outlined some entities which are less well recognised and can lead to typing errors. New variants of seminoma Recently, unusual morphological appearances of seminoma have been described. [20-22] These variants show features that may be confused with non-seminomatous tumours and thereby result in incorrect management. Ulbright and Young have contributed much to the characterisation of these entities. They have described seminoma with microcystic, tubular[22] and signet ring[21] appearances. Immunophenotyping and nuclear morphology in these variant are in keeping with classical seminoma. Usually more classical areas are identified on thorough blocking. With so few cases, the prognostic significance of these variants is not known. Treatment should probably be as for classical seminoma. Spermatocytic seminoma Spermatocytic Seminoma is a well known but rare tumour, first described in the 1940s.[23] Its name is a misnomer in that it is not thought to be a subtype of

9 seminoma but a tumour demonstrating its own unique pathological features and histogenesis. The significance of this entity is that it can be confused with classical seminoma, embryonal carcinoma or lymphoma which would herald unnecessary adjuvant therapy. The tumour tends to follow an indolent course and is adequately treated with orchidectomy alone. However, if sarcomatoid change is seen [24] then the prognosis is poor, but this is extremely rare. Rare case reports exist of metastatic spermatocytic seminoma, which this author steadfastly refused to believe until a recent example occurred in his own practice of a single large lung metastasis. Anaplastic variants of spermatocytic seminoma have been described. However these appear to behave in a similar indolent manner and the challenge relates more to recognition, and not diagnosing these as seminomas. [25] There is intriguing and somewhat contradictory work on the origin of spermatocytic seminomas which was reviewed recently by Looijenga et al.[26] Cytogenetic and PCR studies confirm that tumour cells express proteins that are involved in early spermatogenesis and thus demonstrate a degree of differentiation. The tumour is thought to derive from cells that are able to complete spermatogenesis up to the pachytene stage. In contrast, cells from classical seminoma show complete loss of these proteins supporting embryonic germ cell derivation. [27, 28] Chromosome 9p has been implicated, in contrast to i12p seen in other germ cell tumours. [29] Recent work by Lim et al. shows the heterogeneity of spermatocytic seminoma and suggests that different types of spermatogonia (light or dark as seen in Bouin s fixed material) give rise to these tumours.[30] Therefore separate theories on their origin are yet to be reconciled.

10 Dermoid Cyst Dermoid Cyst of the testis is a rare but benign entity of unknown derivation. The tumour is analogous to the rather more common dermoid cyst of the ovary.[31] It is possible that these tumours derive from germ cells that undergo transformation to differentiated tissue but this is unproven. However it is vital to distinguish these benign neoplasms from mature differentiated teratoma which is capable of metastasis.[32] Unlike its malignant relative, a dermoid cyst is not associated with surrounding IGCNU[31, 33] which is inevitably present around a teratoma.[34] Other features indicative of a malignant lesion are an atrophic testicle with impaired or absent spermatogenesis, regressive changes in the stroma as well as immaturity in the cartilage and other stromal or epithelial elements. By contrast, dermoid cysts are usually surrounded by a normal testicular parenchyma with intact spermatogenesis. The characteristic histological features are those of an epidermis like lining containing pilosebaceous units. Similar to its ovarian counterpart, the tumour can macroscopically manifest as an oily, hair containing cyst. Histogenetic studies extrapolated from ovarian dermoids suggest that these tumours are usually diploid and homozygous[35] whereas mature teratomas show complex chromosomal abnormalities and maybe hypo- or hyper-diploid.[36] Essentially, it is thought that the path taken for a dermoid cyst to develop mature organoid components is one which is entirely different from a mature teratoma and helps to explain the differences in behaviour. [31, 37] The differentiation is far from academic. Dermoids are cured once excised and need no further management. Teratomas require full staging and follow up. They occur more often in younger men, and it has been suggested they are analogous to the mature teratomas seen in prepubescent males.[38] Malignant Sertoli cell tumours which resemble Seminoma

11 Sertoli cells tumours are responsible for <1% of testicular tumours.[39] As a result, their relative rarity may present diagnostic difficulty. A series has been recently described with appearances mimicking seminoma [40] and personal experience, again suggests that this tumour is more common than initially realised. Typical sertoli cell tumours show lipid rich cells arranged in solid or hollow tubules. An inflammatory cell infiltrate of plasma cells may be present amongst the structures[39]. In the series described by Henley et al[40], the clear cells presented histologically as sheets associated with inflammatory cells that were similar to seminoma. In a few cases, the (mis)diagnosis of seminoma had already been made and it was failure of radiotherapy and subsequent metastatic disease that prompted a revisit of the histology. On review, subtle cytological features to differentiate the two tumours could be appreciated such as nuclear size, mitotic count and cellular atypia. Immunohistochemistry has proved valuable in the diagnosis but it remains for the pathologist to be aware of these rare anomalies and direct clinicians appropriately. Immunohistochemistry in germ cell tumours: what s relevant? The vast majority of testicular tumours can be diagnosed adequately without recourse to immunochemistry. The cytological findings and architectural patterns are very distinct, and so long as thorough examination occurs and clinic-pathological correlation occurs, few problems will be encountered. However due to unfamiliarity, pathologists often feel the need to resort to immunochemical back up for their morphological findings. The main new marker in increasing use over the past few years is OCT 3/4, also known as POUSF1, which has proved valuable in the diagnosis of germ cell tumours. [41-43] It is a nuclear transcription factor thought to confer pluripotentiality and maintain viability of stem cells. [44] It is, therefore, present in

12 embryonal cells and human stem cells but the gene is rapidly and permanently defunctioned by DNA methylation once cells are committed to somatic differentiation.[45] Its attraction lies in the fact that it shows very specific staining for seminoma, embryonal carcinoma and IGCNU.[43] Other testicular tumours, showing a greater degree of somatic differentiation, do not demonstrate immunoreactivity and cross reactivity with non germ cell malignancies is extremely low[41]. For example, although it is generally possible to diagnose seminoma on conventional staining, it may occasionally demonstrate architecture mimicking a sertoli cell tumour[40] or yolk sac tumour.[46] OCT 3/4 will not decorate these latter two tumours. Another example of its use is in the identification of a retroperitoneal embryonal carcinoma metastasis and differentiating this from a poorly differentiated carcinoma.[47] Alpha feto-protein is only a patchy marker for yolk sac tumour. Although examination of serum levels of alpha feto-protein will assist in the identification of yolk sac tumour elements, a novel marker, Glypican-3, shows higher specificity and sensitivity.[48] Retroperitoneal lymph node dissection: what s relevant? Retroperitoneal lymph node dissection (RPLND) is performed following adjuvant therapy for stage II disease and above [49] though prophylactic operations for stage 1 disease are performed in some centres in the USA. Histological analysis of this tissue has not only helped understand the effectiveness of adjuvant therapies and the long term behaviour of advanced germ cell tumours but also it has enabled characterisation of the various post chemotherapy changes. While the vast majority of RPLNDs post chemotherapy show either necrosis or teratoma, some unusual findings may cause concern.

13 Late recurrences of yolk sack tumour, post-chemotherapy can demonstrate unusual clear cell, glandular and parietal features which could be confused with other (non germ cell) tumours. [50] These tumours appear to behave in an aggressive fashion. Cystic trophoblastic tumour is an entity thought to be derived from post chemotherapy metastatic choriocarcinoma.[51] The significance of this entity is that although it represents residual malignant disease, further chemotherapy is not indicated as the choriocarcinoma present is cystic and only semi-viable. The decision for further salvage chemotherapy after RPLND is difficult. A number of studies have suggested that excision margin and the volume of embryonal carcinoma or other malignant elements such as yolk sac tumour or choriocarcionoma determine the necessity for further treatment.[52] Prophylactic RPLND is rarely undertaken in Europe. However it has been advocated for malignant non germ cell tumours of the testis, when chemotherapy or radiotherapy is not a viable option.[53] Personal experience of two malignant leydig cell tumours which metastasized widely after expectant treatment has biased this author into at least considering RPLND for non germ cell tumours of the testis with a worrying appearance. Novel treatment strategies: what s relevant? The treatment of germ cell tumours has undergone profound changes in the past ten years. Firstly has been the recognition that many seminomas can be treated by surveillance.[49] Secondly, a hotly debated trial has shown that one or two courses of carboplatin is not inferior to radiation therapy for stage I seminoma.[54] In spite of reservations by senior oncologists[55] on the efficacy and need for this regimen, it is now standard of care in numerous centres and has proved popular in the community as an alternative to radiotherapy.

14 The holy grail of germ cell biology is the identification of those patients who will be resistant to standard platinum based therapies, and who can then be treated initially with a more intensive regimen. A number of functional studies have proposed mechanisms which could in theory be tested in a large population of patients, and then treatments tailored to the tumour genotype.[56, 57] However, this work requires much investment: more than practical in the majority of countries. However, mechanisms of chemotherapy resistance in this, usually chemosensitive tumour, may unlock the door of other more chemoresistant tumours. Conclusions. The combination of rarity and complexity of testicular tumours presents unique challenges to pathologists. The fact that orchiectomy surgery is relatively simple, means that it is not confined to specialist centres and that any diagnostic pathologist may encounter a rare tumour presenting unusual challenges. In the UK it is now recommended that all tumours be centrally reviewed by supra-regional experts in this field. This is probably not feasible in other countries, but nevertheless it is vital to have an awareness of those relevant areas that may cause diagnostic errors and lead to inappropriate treatment. References 1. Sobin, L.H. and C. Wittekind, eds. TNM Classification of Malignant Tumours. 6 ed. 2002, Wiley-Liss: New York. 2. Parker, C., et al., The prognostic significance of the tumour infiltrating lymphocyte count in stage I testicular seminoma managed by surveillance. Eur J Cancer, (15): p

15 3. von der Maase, H., et al., Surveillance following orchidectomy for stage I seminoma of the testis. Eur J Cancer, A(14): p Warde, P., et al., Prognostic factors for relapse in stage I seminoma managed by surveillance: a pooled analysis. J Clin Oncol, (22): p Lee, A.H. and J.M. Theaker, Pagetoid spread into the rete testis by testicular tumours. Histopathology, (4): p Due, W. and V. Loy, Evidence of interepithelial seminoma spread into the rete testis by immunostaining of paraffin sections with antibodies against cytokeratin and vimentin. Urol Res, (5): p Browne, T.J., et al., Intertubular growth in pure seminomas: associations with poor prognostic parameters. Hum Pathol, (6): p Choo, R., et al., Long-term outcome of postorchiectomy surveillance for Stage I testicular seminoma. Int J Radiat Oncol Biol Phys, (3): p Fossa, S.D., et al., How safe is surveillance in patients with histologically lowrisk non-seminomatous testicular cancer in a geographically extended country with limited computerised tomographic resources? Br J Cancer, (6): p Dunphy, C.H., et al., Clinical stage I nonseminomatous and mixed germ cell tumors of the testis. A clinicopathologic study of 93 patients on a surveillance protocol after orchiectomy alone. Cancer, (6): p Colls, B.M., et al., Late results of surveillance of clinical stage I nonseminoma germ cell testicular tumours: 17 years' experience in a national study in New Zealand. BJU Int, (1): p Alexandre, J., et al., Stage I non-seminomatous germ-cell tumours of the testis: identification of a subgroup of patients with a very low risk of relapse. Eur J Cancer, (5): p Wishnow, K.I., et al., Identifying patients with low-risk clinical stage I nonseminomatous testicular tumors who should be treated by surveillance. Urology, (6): p Atsu, N., et al., A novel surveillance protocol for stage I nonseminomatous germ cell testicular tumours. BJU Int, (1): p Nicolai, N. and G. Pizzocaro, A surveillance study of clinical stage I nonseminomatous germ cell tumors of the testis: 10-year followup. J Urol, (3): p Read, G., et al., Medical Research Council prospective study of surveillance for stage I testicular teratoma. Medical Research Council Testicular Tumors Working Party. J Clin Oncol, (11): p

16 17. Ernst, D.S., et al., Compliance and outcome of patients with stage 1 nonseminomatous germ cell tumors (NSGCT) managed with surveillance programs in seven Canadian centres. Can J Urol, (2): p Grossfeld, G.D. and E.J. Small, Long-term side effects of treatment for testis cancer. Urol Clin North Am, (3): p Nazeer, T., et al., Spermatic cord contamination in testicular cancer. Mod Pathol, (7): p Young, R.H., Testicular tumors--some new and a few perennial problems. Arch Pathol Lab Med, (4): p Ulbright, T.M. and R.H. Young, Seminoma with conspicuous signet ring cells: a rare, previously uncharacterized morphologic variant. Am J Surg Pathol, (8): p Ulbright, T.M. and R.H. Young, Seminoma with tubular, microcystic, and related patterns: a study of 28 cases of unusual morphologic variants that often cause confusion with yolk sac tumor. Am J Surg Pathol, (4): p Masson, P., Etude sur le seminome. Rev Can Biol, (4): p True, L.D., et al., Spermatocytic seminoma of testis with sarcomatous transformation. A report of five cases. Am J Surg Pathol, (2): p Dundr, P., et al., Anaplastic variant of spermatocytic seminoma. Pathol Res Pract, (8): p Looijenga, L.H., Spermatocytic seminoma: toward further understanding of pathogenesis. J Pathol (4): p Looijenga, L.H. and J.W. Oosterhuis, Pathogenesis of testicular germ cell tumours. Rev Reprod, (2): p Stoop, H., et al., Reactivity of germ cell maturation stage-specific markers in spermatocytic seminoma: diagnostic and etiological implications. Lab Invest, (7): p Looijenga, L.H., et al., Genomic and expression profiling of human spermatocytic seminomas: primary spermatocyte as tumorigenic precursor and DMRT1 as candidate chromosome 9 gene. Cancer Res, (1): p Lim, J., et al., OCT2, SSX and SAGE1 reveal the phenotypic heterogeneity of spermatocytic seminoma reflecting distinct subpopulations of spermatogonia. J Pathol (4): p

17 31. Ulbright, T.M. and J.R. Srigley, Dermoid cyst of the testis: a study of five postpubertal cases, including a pilomatrixoma-like variant, with evidence supporting its separate classification from mature testicular teratoma. Am J Surg Pathol, (6): p Simmonds, P.D., et al., Primary pure teratoma of the testis. J Urol, (3): p Dieckmann, K.P. and V. Loy, Epidermoid cyst of the testis: a review of clinical and histogenetic considerations. Br J Urol, (4): p Manivel, J.C., et al., Intratubular germ cell neoplasia in testicular teratomas and epidermoid cysts. Correlation with prognosis and possible biologic significance. Cancer, (3): p Surti, U., et al., Genetics and biology of human ovarian teratomas. I. Cytogenetic analysis and mechanism of origin. Am J Hum Genet, (4): p Looijenga, L.H., et al., Dual parameter flow cytometry for deoxyribonucleic acid and intermediate filament proteins of residual mature teratoma. All tumor cells are aneuploid. Lab Invest, (1): p Ulbright, T.M., Germ cell tumors of the gonads: a selective review emphasizing problems in differential diagnosis, newly appreciated, and controversial issues. Mod Pathol, Suppl 2: p. S Kendall, T.J., et al., Case series: adult testicular dermoid tumours--mature teratoma or pre-pubertal teratoma? Int Urol Nephrol, (3-4): p Ulbright, T.M., Berney D.M., Testicular and Paratesticular Tumors, in Sternberg's Diagnostic Surgical Pathology, S.E. Mills, Editor. 2009, Lippincott, Williams and Wilkins. 40. Henley, J.D., R.H. Young, and T.M. Ulbright, Malignant Sertoli cell tumors of the testis: a study of 13 examples of a neoplasm frequently misinterpreted as seminoma. Am J Surg Pathol, (5): p Looijenga, L.H., et al., POU5F1 (OCT3/4) identifies cells with pluripotent potential in human germ cell tumors. Cancer Res, (9): p Jones, T.D., et al., OCT4: A sensitive and specific biomarker for intratubular germ cell neoplasia of the testis. Clin Cancer Res, (24): p Jones, T.D., et al., OCT4 staining in testicular tumors: a sensitive and specific marker for seminoma and embryonal carcinoma. Am J Surg Pathol, (7): p

18 44. Nichols, J., et al., Formation of pluripotent stem cells in the mammalian embryo depends on the POU transcription factor Oct4. Cell, (3): p Pesce, M. and H.R. Scholer, Oct-4: gatekeeper in the beginnings of mammalian development. Stem Cells, (4): p Eglen, D.E. and T.M. Ulbright, The differential diagnosis of yolk sac tumor and seminoma. Usefulness of cytokeratin, alpha-fetoprotein, and alpha-1- antitrypsin immunoperoxidase reactions. Am J Clin Pathol, (3): p Cheng, L., Establishing a germ cell origin for metastatic tumors using OCT4 immunohistochemistry. Cancer, (9): p Zynger, D.L., et al., Glypican 3 has a higher sensitivity than alpha-fetoprotein for testicular and ovarian yolk sac tumour: immunohistochemical investigation with analysis of histological growth patterns. Histopathology (6): p Schmoll, H.J., et al., European consensus on diagnosis and treatment of germ cell cancer: a report of the European Germ Cell Cancer Consensus Group (EGCCCG). Ann Oncol, (9): p Michael, H., et al., The pathology of late recurrence of testicular germ cell tumors. Am J Surg Pathol, (2): p Ulbright, T.M., et al., Cystic trophoblastic tumor: a nonaggressive lesion in postchemotherapy resections of patients with testicular germ cell tumors. Am J Surg Pathol, (9): p Berney, D.M., et al., Prediction of relapse after lymph node dissection for germ cell tumours: can salvage chemotherapy be avoided? Br J Cancer, (3): p Mosharafa, A.A., et al., Does retroperitoneal lymph node dissection have a curative role for patients with sex cord-stromal testicular tumors? Cancer, (4): p Oliver, R.T., et al., Randomized trial of carboplatin versus radiotherapy for stage I seminoma: mature results on relapse and contralateral testis cancer rates in MRC TE19/EORTC study (ISRCTN ). J Clin Oncol (8): p Bosl, G.J. and S. Patil, Carboplatin in clinical stage I seminoma: too much and too little at the same time. J Clin Oncol (8): p Noel, E.E., et al., The association of CCND1 overexpression and cisplatin resistance in testicular germ cell tumors and other cancers. Am J Pathol (6): p

19 57. Honecker, F., et al., Microsatellite instability, mismatch repair deficiency, and BRAF mutation in treatment-resistant germ cell tumors. J Clin Oncol, (13): p Table 1 TNM 2010 Classification ptx: The primary tumor cannot be evaluated. If a man has not had a radical inguinal orchiectomy (surgical removal of the testicle[s]), the term "TX" is used. pt0: There is no evidence of a primary tumor in the testicles. ptis: Intratubular germ cell neoplasia pt1: The primary tumor is confined to the testicle (with or without involvement of the epididymis or rete testis), and it has not invaded blood vessels or lymph vessels in the testicles. The tumor may have invaded the tunica albuginea but not the tunica vaginalis. pt2: The tumor is in the testicle (with or without involvement of the epididymis or rete testis) and has invaded blood vessels or lymphatic vessels, and/or the tumor has grown through the tunica albuginea and into the tunica vaginalis. pt3: The tumor has invaded the spermatic cord. pt4: The tumor has invaded the scrotum Learning points Current prognostic models include factors not considered in current TNM staging which need to be evaluated such as rete testis invasion and tumour size Macroscopic examination of the testis should prioritise good fixation and tumour typing over minutiae of staging Unusual variants may mimic other tumour types. This is a particular challenge in seminoma and its mimics. New entities, such as dermoid cyst or cystic trophoblastic tumour, if properly evaluated, may prevent the overtreatment of benign lesions. More specific and sensitive immunochemical markers such as OCT3/4 are recommended.