Histopathology: neoplasia

Transcription

1 Histopathology: neoplasia These presentations are to help you identify basic histopathological features. They do not contain the additional factual information that you need to learn about these topics, or necessarily all the images from resource sessions. This presentation contains images of basic histopathological features of neoplasia. Before viewing this presentation you are advised to review relevant sections of a pathology textbook, relevant lecture notes and relevant sections of a histopathology atlas. Copyright University of Adelaide 2011 (The histopathology of neoplasia is mainly introduced in semester 2, year 2)

2 Neoplasia refers to the unregulated proliferation of cells that are not responding to the normal control mechanisms of the body. After birth, normal mature or fully differentiated cells develop from normal less differentiated precursor or stem cells. The stem cells replicate to replenish their population and develop specialized features and functions as they mature or differentiate into specialised cell types. Normal cell proliferation and differentiation are tightly regulated by the proteins encoded by numerous genes. Neoplasia develops from the stepwise acquisition of a variety of genetic alterations over time in a single cell that eventually lead to excessive proliferation, failure to respond to signals controlling proliferation and normal differentiation, and also to acquisition of other abnormal cell characteristics. Neoplastic cells probably arise from the precursor cells in a tissue (rather than the mature cells) and then differentiate towards a specific cell type of that tissue, but their differentiation is incomplete or abnormal and proliferation is uncontrolled. Neoplastic changes are permanent/irreversible.

3 Neoplastic lesions are subdivided into 2 main groups depending on their potential behaviour: benign and malignant. Benign lesions Local expansile growth, generally well circumscribed Unable to metastasize Comprise cells that are well differentiated i.e. resemble mature cells, with cell and nuclear uniformity (little pleomorphism), and generally little mitotic activity No necrosis (unless infarcted, ulcerated) Usually able to be removed completely, if need to be removed at all, but some can recur if incompletely excised

4 Malignant lesions Locally invasive, destructive growth, often poorly circumscribed with irregular margins. Growth may be rapid Able to metastasize Tumour cells may be well, moderate or poorly differentiated or completely undifferentiated (anaplastic). More poorly differentiated cells show fewer features of differentiation, larger nuclei, greater nuclear pleomorphism, prominent nucleoli and more mitotic activity (+/- atypical mitoses) than more well differentiated cells. The degree of differentiation of a malignant tumour (the resemblance that the cells show to mature cells) is referred to as its grade Sometimes demonstrate necrosis Depending on the type, often difficult or impossible to cure once metastasised

5 Compare the epithelial cells from the normal colonic glands in the image on the left to those in the colonic adenocarcinoma on the right. Note that the normal epithelial cells have small nuclei that are similar in size to each other (blue arrows) and only take up about one third of the cell. The malignant nuclei are larger (red arrows) and take up a larger proportion of the cell (higher nuclear:cytoplasmic (N:C) ratio), and there is much greater variability in size between nuclei and the cells themselves (pleomorphism). The malignant cells, however, still show their glandular nature by the formation of glandular lumina (red stars). This is a moderately differentiated adenocarcinoma. Benign lesions and well differentiated malignancies will show less nuclear atypia.

6 Compare the epithelial cells from the normal colonic gland on the left to those of the benign neoplastic gland on the right. Note that the normal epithelial cells have small nuclei that are similar in size to each other (grey arrows) and only take up about one third or less of the cell. The well differentiated neoplastic nuclei are larger and more crowded (red arrows) and take up a larger proportion of the cell. There is only mild nuclear pleomorphism. The epithelial basement membranes are outlined in black. Note the capillaries (blue arrows) and plasma cells (white arrows) in the lamina propria.

7 Compare the nuclei of the cells from the leiomyoma - a benign smooth muscle neoplasm (image on left) to those of the moderately differentiated leiomyosarcoma (image on right). The cells in the left image have fairly orderly uniform nuclei (e.g. blue arrows) whilst on the right some nuclei are larger and there is moderate nuclear pleomorphism (red arrows). Note also that the malignant nuclei demonstrate hyperchromatism - deeper haematoxylin staining, than the benign nuclei - another common feature of malignant cells due to their typically increased DNA content, and the chromatin is coarsely clumped. On high power, the cells of a leiomyoma are essentially indistinguishable from normal smooth muscle cells.

8 The nuclear size of any cell can be compared with other cells in the same section. Compare the huge nuclei (red arrows, one nucleus is outlined in black) in this malignant lesion to those of the normal lymphocytes infiltrating the lesion (e.g. yellow arrows). Note also the prominent nucleoli (blue arrows) in the nuclei of the malignant cells, another feature common to malignancy, especially less well differentiated ones. Nucleoli, being the ribosome factories of the cell, normally are prominent in cells undergoing protein synthesis.

9 Extreme nuclear pleomorphism (here in a malignant melanoma). Note variability in nuclear size and shape (red arrows).

10 Malignant lesions also frequently demonstrate necrosis, which may or may not be visible macroscopically. The necrotic area here is outlined in black. The dead cells are shrunken and more eosinophilic than the viable cells and they have karyorrhectic (pyknotic and fragmented) nuclei. Cell death in malignancy may be via apoptosis (where tumour cells are destroyed by CD8 T cells) or by necrosis (thought to be from tumour cells outgrowing their blood supply).

11 Mitoses are also seen in neoplastic lesions. Condensed chromosomes are seen in a cell (blue arrow) in the image on the left and 2 sets of fully formed chromosomes (red arrow) are seen ready to separate into two separate cells in the image on the right. The number of mitoses tends to increase as differentiation becomes less. Malignancies may contain mitotic figures with abnormal morphology. What cell types are indicated by the white and yellow arrows in the right image? (Answer: White: plasma cells. Yellow: neutrophils)

12 In addition to showing cytological (i.e. cellular) atypia, neoplastic lesions (especially malignant) also show architectural atypia i.e. there is disorganisation of the components of the lesion. The image above is from a colonic biopsy. A few normal glands are present (outlined in black). They are somewhat crosscut but you can see the simple glandular structures. The remainder of the tissue is invasive adenocarcinoma. Note how the malignant glands (red star) are more closely packed and disorganised, the glands are probably branching. Note also how, although this is fairly low power, goblet cells are seen in the normal epithelium, but not in the malignant epithelium. This indicates that the malignant epithelium is not as well differentiated.

13 As malignant cells grow they need a blood supply and supportive connective tissue stroma. The stroma that develops looks different to the normal connective tissue of the region that the tumour invades. The stromal/fibrous response within an invasive malignancy is known as desmoplasia. When florid, this stromal response makes the tumour very firm and pale (e.g. schirrous ductal carcinoma of the breast). A desmoplastic stromal response is seen here in the invasive colonic adenocarcinoma (image on left) where there are more fibroblasts and denser connective tissue (red stars) than in the normal looser connective tissue of the lamina propria and submucosa (yellow stars) of normal colon (image on right). Assessment of the stroma around atypical cells can sometimes help a pathologist to determine if they are invasive or not. Chronic inflammatory cells also infiltrate malignant and often benign lesions.

14 Ulcerated area M MP Invasive tumour A Normal colon Most neoplastic lesions form a mass that is composed not only of neoplastic cells but also supportive stroma, blood vessels and often chronic inflammatory cells. The image on the left is a macroscopic view of an adenocarcinoma of the colon (red star). The tumour surface is ulcerated. The image on the right is a very low power histopathological view of the edge of such a lesion. The tumour is on the left side of the black line and normal colon is on the right side. Note how the tumour cells (seen as dark blue/purple areas due to their high N:C ratio) invade deeply into the adventitia (A). The eosinophilic staining between the groups of tumour cells represents the tumour stroma. (M: mucosa, MP muscularis propria)

15 A B Tumour Lung Most neoplastic lesions form a mass that is composed not only of neoplastic cells but also supportive stroma, blood vessels and often chronic inflammatory cells. The image on the left (A) is of a primary carcinoma of the lung (blue star) that has metastasised extensively to hilar and paratracheal lymph nodes (red stars). The image on the right (B) is a very low power histopathological view of the edge of a primary lung carcinoma, in this case adenocarcinoma, invading lung tissue. The image could have been taken from an area such as that outlined by the black box in image A. In image B, the tumour cells are the dark purple cells forming glandular lumina. The paler purple is stroma and the very dark dots (black stars) is an extensive lymphocytic infiltrate.

16 Neoplastic lesions are named according to their line of differentiation and their likely behaviour (benign or malignant). These can to some extent be assessed macroscopically, but frequently lesions are biopsied for histopathological examination and definitive diagnosis. Before treatment begins, presumed malignant lesions require pathological confirmation of their malignant nature. The pathologist examines the histological architecture, cytological features and invasive nature of the lesion to determine if it is benign or malignant. In difficult cases they may also need to look for necrosis, the features of the stroma, or to count mitotic figures. They also need to determine the type of lesion, or its line of differentiation (glandular, melanocytic etc) and to grade malignant lesions (usually) as these features also influence the management of the patient and prognosis. Other prognostic features may also need to be assessed. Neoplastic cells demonstrate morphological and functional features of the cells from which they have arisen (as they are genetically programmed to do this), which are thought to be the stem or progenitor cells within a tissue that normally give rise to the mature cells of that tissue. The tumour is named according to the features of differentiation that the cells demonstrate histologically (line of differentiation) though these are normally the same as the cell type in which the lesion arose. However, the genetic control of these neoplastic cells is abnormal so the cells not only proliferate uncontrollably, they do not differentiate normally so will not appear completely mature. The more uncontrolled the differentiation, the more poorly differentiated (and more aggressive) the tumour will be. There are several main groups of neoplastic lesions including epithelial, mesenchymal, lymphoid, germ cell etc and these have benign and malignant forms of which there are many different subtypes. The terminology of neoplastic lesions (both benign and malignant) follows certain rules (to which there are many exceptions), generally giving an indication as to their line of differentiation and benign or malignant nature. You should understand these rules and the common exceptions.

17 Adenocarcinoma of cervix Adenocarcinoma of lung Carcinomas are malignant epithelial lesions. There are many types. Adenocarcinomas demonstrate glandular epithelial differentiation. This is normally demonstrated by the formation of glandular lumina (black arrows) by the tumour cells seen here in the low power images. Adenocarcinomas are one of the commonest types of malignancy and may arise in the colon, prostate, breast, lung, stomach, pancreas, cervix, uterus et al. Often the adeno is dropped from the name so it becomes e.g. colorectal carcinoma, ductal carcinoma of the breast.

18 There are different types of adenocarcinoma, however, that have different prognostic significance. While most demonstrate their glandular nature by the formation of glandular lumina (black arrows), in others the malignant cells contain a large droplet of mucin that pushes the nucleus to the side (yellow arrows). These are known as signet ring (adeno)carcinomas. In others the cells secrete abundant mucin (red stars) and the malignant cells (red arrows) float about within it. These are known as mucinous or colloid (adeno)carcinomas.

19 B A D B C Squamous cell carcinomas (SCC) demonstrate squamous epithelial differentiation. This is typically demonstrated by many of the cells having abundant eosinophilic cytoplasm, the presence of intercellular bridges (black arrows, difficult to see) between the tumour cells and the formation of keratin pearls (D). These features resemble those of keratinising stratified squamous epithelium. In fact, within the masses and islands of tumour cells in invasive SCCs (at least well and moderately differentiated ones), cells at all stages of squamous differentiation as in keratinising stratified squamous epithelium can sometimes be seen. On the outer edge of tumour islands are basal cell like cells (A). As they mature towards the inner part of the island, they develop abundant eosinophilic cytoplasm and intercellular bridges as do cells of the stratum spinosum (B) and sometimes even keratohyaline granules (yellow arrows) within a stratum granulosum like layer (C) are seen. Ultimately the cells may keratinise and lose their nuclei in the centre of the island (D) as do normal superficial squamous cells. Such a rounded mass of keratin is called a keratin pearl. Many lymphocytes surrounding the island of tumour cells are noted here (yellow star).

20 SCC of skin Tumour SCC of cervix Normal skin Squamous cell carcinomas (SCC) are also very common. They can arise in the skin, lung, oral cavity, pharynx, larynx, oesophagus, anus, cervix, vagina, vulva et al. SCC of cervix (low power): note the surface stratified squamous epithelium (black arrow) and masses of eosinophilic tumour cells invading the underlying stroma, some of which demonstrate keratinisation (black star). SCC of skin: very low power view of the edge of an SCC of skin. Note also hair follicle (yellow arrow), sebaceous glands (blue arrows) and sweat glands (red arrows).

21 The cells of carcinomas tend to be polygonal, oval or rounded. Sarcomas (showing features of cell types normally derived from embryonic mesoderm) tend to be composed of more elongate or spindled cells with elongated nuclei. The image here exhibits a moderately differentiated leiomyosarcoma.

22 The following 2 slides list many of the different types of malignancy. You do not need to learn this, just know the main groups and appreciate that classification is complex. The different types tend to occur in different locations, in different age groups etc. Likewise the classification of benign tumours is complex.

23 Classification of malignancy Carcinoma Squamous cell carcinoma Usual (not otherwise specified) Basaloid Spindle/sarcomatoid Adenoid Adenosquamous Verrucous Adenocarcinoma Usual (not otherwise specified) Mucinous/colloid Signet ring Adenoid cystic Clear cell Endometrioid Papillary Mucoepidermoid carcinoma Bronchioloalveolar carcinoma (lung), Sweat gland carcinoma (skin) Sebaceous carcinoma (skin) Nasopharyngeal carcinoma Cholangiocarcinoma Adenosquamous carcinoma Basal cell carcinoma, various subtypes: superficial, sclerosing, other Hepatocellular carcinoma: various subtypes Ductal (breast) and subtypes (many show adenocarcinoma pattern): e.g. tubular, secretory, cribriform Lobular (breast): various subtypes Renal cell carcinoma: various subtypes (many show adenocarcinoma pattern) Follicular carcinoma of thyroid: various subtypes Papillary carcinoma of thyroid: various subtypes Extramammary Paget s disease Thymic carcinoma: various subtypes Giant cell carcinoma Undifferentiated carcinoma Transitional cell/urothelial carcinoma Neuroendocrine carcinoma Carcinoid tumour Atypical carcinoid tumour Large cell neuroendocrine carcinoma Oat cell/small cell undifferentiated Medullary carcinoma (thyroid) Endocrine carcinoma Malignant pancreatic islet cell tumours Parathyroid carcinoma Adrenocortical carcinoma Malignant Leydig cell tumour Malignant granulosa cell tumours Other

24 Classification of malignancy Sarcoma Angiosarcoma Leiomyosarcoma Rhabdomyosarcoma: various subtypes Osteosarcoma: various subtypes Chondrosarcoma: various subtypes Liposarcoma: various subtypes Synovial sarcoma Epithelioid sarcoma Malignant fibrous histiocytoma: various subtypes Malignant peripheral nerve sheath tumour Endometrial stomal tumours Malignant phyllodes tumours Other Carcinosarcomas e.g. malignant mixed mullerian tumour Germ cell tumours Yolk sac tumour Choriocarcinoma Embryonal cell carcinoma Mature and immature teratomas Seminoma/dysgerminoma Tumours of neuroepithelial tissue Astrocytoma Various grades of astrocytoma including glioblastoma multiforme Other subtypes Oligodendroglioma Ependymoma plus various subtypes Choroid plexus carcinoma Embryonal tumours Medulloblastoma Primitive neuroectodermal tumours Neuroblastoma Lymphoma Hodgkin's lymphoma Lymphocyte rich Nodular sclerosing Mixed cellularity Lymphocyte depleted Other Wilm s tumour (nephroblastoma) Retinoblastoma Hepatoblastoma Primitive neuroectodermal tumour/ewing s sarcoma Malignant phaeochromocytoma and paraganglioma Multiple myeloma Malignant meningioma Mesothelioma Melanoma: Subtypes: superficial spreading, nodular, acral lentiginous, melanoma arising in a Hutchinson s melanotic freckle,spindled, spitzoid, other Other Non-Hodgkin's lymphoma: Numerous subtypes e.g. diffuse large cell, anaplastic, Burkitt s, well differentiated lymphocytic Leukaemias Many subtypes

25 Most neoplastic lesions form a mass that is composed not only of neoplastic cells but also supportive stroma, blood vessels and often chronic inflammatory cells. Benign tumours (green star) tend to form lesions with well defined borders as they expand locally, and malignant tumours (red star) tend to have more ill-defined margins that infiltrate and destroy adjacent tissue. Necrosis may also be visible macroscopically in malignant tumours. There are many exceptions, however, and while the macroscopic features can be used in helping to make a diagnosis, if there is suspicion of malignancy, or definitive diagnosis is required, the cells of the lesion need to be examined under the microscope by a pathologist.

26 A B C Biopsies are pieces of tissue that are taken from a lesion in order to examine it under a microscope. Biopsies can be taken via a number of ways. Small pieces of tissue 2-3 mm in diameter can be taken at endoscopy such as in image A - a biopsy of a rectal adenocarcinoma. Lesions can be removed in their entirety (image B - excision biopsy). Image C demonstrates part of a needle core biopsy of the liver. Such cores are 10-20mm in length and 1-2mm in diameter. (B: from Australian Cancer Society). Such biopsies give intact pieces of tissue that can be assessed histologically.

27 A B Cytological specimens. Cells from a lesion may be aspirated, or the cells that are shed from a surface collected. The cells are then put onto a slide, fixed, stained and examined. These cells will to a large extent have lost their architectural relationship to other cells. This form of examination is known as cytology (as opposed to histopathology where portions of tissue are examined). Nonetheless, cytological features of malignancy and features of differentiation can be seen. Image A demonstrates cells with large nuclei (black arrows, compare with the lymphocytes in the background) and little cytoplasm that focally form a small gland or acinus (red arrow). This is an adenocarcinoma. Macrophages are also noted (yellow arrows). Image B shows cells with large pleomorphic nuclei (compare with neutrophils in background) and moderate amounts of cytoplasm that stains pink with this special Pap stain - this is a squamous cell carcinoma.

28 1 2 3 The images here demonstrate degrees of differentiation of smooth muscle lesions. 1 is from a very well differentiated lesion, closely resembling normal smooth muscle, 2 is moderately differentiated and 3 is poorly differentiated (difficult to tell if it is smooth muscle at all). The degree of differentiation or grade indicates how aggressive a tumour is likely to be. Differentiation is assessed histologically i.e. it is not appropriate to use the term poorly differentiated in a macroscopic description.

29 Hepatocytes H&E Tumour S100 LCA CAM5.2 Sometimes malignancies look very similar under the microscope or are so poorly differentiated that the pathologist cannot determine what type it is from the light microscopic features alone. Immunohistochemistry can then be used to determine what proteins the tumour cells contain. This varies depending on their line of differentiation. Immunohistochemistry uses labelled antibodies to bind to and highlight these specific proteins. The images here are from sections of a tumour that has metastasised to the liver. In each image hepatocytes are on the left and tumour on the right (continued next page).

30 S100 Hepatocytes Tumour LCA CAM5.2 Immunohistochemistry has been performed on these sections. Specific antibodies with an enzyme attached are added to the sections. The antibodies attach to the specific proteins and the remaining antibody is washed off. The enzyme catalyses a colour change reaction upon addition of the substrate. In this case, the regions where the antibodies have attached stain brown. LCA is a protein in cells showing lymphoid differentiation - here the tumour cells do not stain but infiltrating lymphocytes do. The tumour is thus not lymphoma. CAM5.2 identifies cytokeratin intermediate filaments present in cells showing epithelial differentiation - the tumour cells are negative but adjacent hepatocytes are positive as would be expected. The tumour is thus not carcinoma. S100 mainly identifies cells showing melanocytic differentiation - the tumour cells are positive which in addition to the other immunohistochemical features is in keeping with the tumour being a melanoma.

31 Metastases. Malignant cells are able to metastasise to a wide variety of sites. They mainly do this by invading lymphatics and/or capillaries or small veins. Malignant cells (red stars) are seen here in small vessels either side of the muscularis mucosae (MM) in the colon. It is not possible to determine if these are lymphatic or blood vessels. Compare the size of the tumour cell nuclei to those of the normal colonic epithelium (yellow stars). The tumour is an adenocarcinoma - as seen by the large mucin droplets in a number of the cells (black arrows). Identification of such vascular invasion has prognostic significance as it suggests that the tumour has metastasised even if no metastases can be identified in scans. Also note the lymphocytes and plasma cells (normal) of the lamina propria, but some now infiltrate into submucosa around the tumour (bottom of image). MM

32 Liver Metastatic adenocarcinoma Lymph node Metastatic SCC Metastatic adenocarcinoma Lymph node The metastatic tumour shows the same histopathologic features as the primary tumour.

33 Once a diagnosis has been made, unless it has already metastasised widely, malignant lesions are often removed in their entirety, as typically are one (sentinal node) or more lymph nodes in the lymphatic drainage pathway. This is done in an attempt to cure the patient and also to find out more about the nature of the tumour and its stage. There are many features that influence the prognosis and management of a patient with malignancy. These include the type of tumour, the stage and grade (and other features depending on the tumour). The pathologist reporting the surgically removed specimen plays a significant role in determining these features which appear in their pathology report. For major malignancies these are usually summarised in a synoptic report. An example of a synoptic report of a colorectal carcinoma follows on the next 2 pages. Medical students should look at all laboratory reports in patient s medical records and learn to understand them.

34 Colorectal Cancer Resection Specimen Synoptic Report Clinical Summary: Partial colectomy and end ileostomy for caecal Ca Pathological Diagnosis: Invasive moderately differentiated adenocarcinoma invading into muscularis propria. Three adenomas showing severe dysplasia. Local excision complete. 0/23 nodes involved. Comments: Macroscopic: The specimen consists of a 30mm segment of terminal ileum, 210mm portion of caecum and ascending colon and attached pericolonic fat. Appendix is not identified. The caecum contains an ulcerated fungating 30x27mm diameter tumour 20mm from the ileocaecal junction.the overlying serosa appears congested. Three sessile polyps 5-10mm in diameter are present in the ascending colon. Ax1: proximal margin, Bx1 distal margin, C-Fx1 tumour, G-Ix1 polyps, Jx3, Kx1, Lx3, Mx4, Nx2, Ox1, Px3, Qx4, Rx2 lymph nodes. Nature of specimen: Right hemicolectomy. Tumour site: Caecum Tumour size: 30x27mm Proximal dilation (obstruction): Absent Perforation: Absent Tumour type: Adenocarcinoma NOS Grade: Moderately differentiated Margin of tumour: Infiltrative Inflammatory infiltrate: Present

35 Colorectal Cancer Resection Specimen Synoptic Report LOCAL SPREAD: Depth of invasion: Into muscularis propria Excision margins: Proximal and distal margins are free of tumour Pathological staging: Vascular invasion: Not identified Neural invasion: Not identified DISTANT SPREAD: Lymph nodes: Total number of nodes found: 23 Total number of nodes involved by tumour: 0 Apical node: Not involved Mesenteric deposits: Absent Adjacent bowel: 3x adenomatous polyps showing severe dysplasia Ancillary investigations

36 Many SCCs, adenocarcinomas and transitional/urothelial carcinomas (in bladder and ureters) start off life as an intraepithelial abnormality known as dysplasia (often, depending on location, known as intraepithelial neoplasia). Such dysplasia is characterized by increased cellular proliferation, cellular atypia and incomplete maturation/differentiation of the cells, with architectural disorganisation. It arises due to initial alterations in genes regulating cell division. In its early stages it is potentially reversible but as further genetic alterations are acquired, the dysplasia worsens and the atypical cells may then acquire features necessary to invade the basement membrane, becoming malignant. The changes of dysplasia are confined to the epithelium: there is no invasion through the basement membrane. The severity of dysplasia can be graded histologically - usually there are 3 grades: 1-3, or mild, moderate or severe. Severe or grade 3 dysplasia in many locations is referred to as in situ carcinoma (or carcinoma in situ). In different situations, dysplasia is referred to as being non-neoplastic, pre-neoplastic, pre-malignant or intraepithelial neoplasia. It is perhaps most helpful to think of it as being a benign (as it is not invasive and does not have the potential to metastasise) neoplastic lesion that has the potential to become malignant, but which does not necessarily form a mass/tumour. Malignant cells are not referred to as being dysplastic.

37 Images from the cervix (high power). Image on left: Normal non-keratinising stratified squamous epithelium. The more cuboidal/columnar basal cells become flatter as they migrate towards the surface. The cells in the middle and surface of the epithelium have a very low nuclear:cytoplasmic ratio. Image on right: Severe squamous dysplasia (cervical intraepithelial neoplasia 3). The cells through the full thickness of the epithelium have a high N:C ratio and there is little flattening off of the cells as they differentiate towards the surface, indicating lack of normal differentiation. Normal endocervical glands lined by simple columnar mucus secreting epithelium in the underlying stroma are indicated by black arrows. Basement membranes are indicated (approx.) by black lines.

38 Image from the cervix (high power). Mild squamous dysplasia (cervical intraepithelial neoplasia 1). Disorganised dysplastic cells are confined to the lower one third of the epithelium. The vacuolated cells in the middle and upper one thirds of the epithelium are koilocytes - HPV infected cells with large irregular nuclei and vacuolated cytoplasm.

39 Keratinizing stratified squamous epithelium of the epidermis (medium power view). The black line separates normal from dysplastic epithelium. Normal epidermis is on the right. The normal stratum granulosum is clearly seen (black star). The dysplastic epithelial cells on the left are more disorganised, some have larger nuclei and the cells are proliferating and differentiating more quickly, as seen by the absence of the stratum granulosum and the retention of nuclei in the stratum corneum (yellow star). Epidermal dysplasia is normally induced by chronic sun exposure. It is very common. Such lesions are called solar or actinic keratoses.

40 Low power view of bronchus. A continuum of squamous metaplasia (blue arrow) -> dysplasia (black arrow) -> invasive squamous cell carcinoma (red stars) can be seen in this low power view of bronchus. Normal respiratory epithelium is indicted by the green arrow. Note how the dysplastic epithelium and invasive carcinoma appear bluer compared to the metaplastic stratified squamous epithelium (pinker) due to the higher N:C ratio of the cells. Green star: seromucus glands. Yellow stars: cartilage.

41 Cells from a cervical smear. Dysplastic changes can also be seen on cytology. Black arrow: normal squamous epithelial cell with low N:C ratio. Red arrow: 2 severely dysplastic squamous epithelial cells with irregular large nuclei and high N:C ratio.

42 Glandular dysplasia in the colon (high power). Normal epithelium is present in the gland on the left and dysplastic epithelium on the right. The dysplastic cells have larger nuclei (red arrows) that take up a greater proportion of the cell. They are also more crowded. The black arrows indicate the smaller more uniform nuclei of the normal cells.

43 Glandular dysplasia in the colon (low power). Normal glands are present on the right and dysplastic glands on the left. The black line separates them. The dysplastic glands are more elongated, branched and disorganised. There are also fewer goblet cells indicating less differentiation. MM: muscularis mucosae. MM

44 Polyp Normal mucosa Submucosa While squamous dysplasia does not form a mass, glandular dysplasia often forms a polyp - a protuberance of tissue elevated from the surrounding mucosa. Such dysplastic polyps are often referred to as adenomatous polyps or just adenoma. Note how the glands of the polyp (very low power view) are elongated and irregular compared to the normal glands. (N.B. Not all adenomas are dysplastic. Adenomas in the GIT are dysplastic but adenomas in other sites are typically not dysplastic e.g. breast).