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| Malignant
Melanoma: Diagnostic Histopathology Criteria |
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I. General Histological Criteria for any melanoma
| size: |
breadth usually >6 mm. at biopsy |
| shape: |
asymmetry; variable colors |
| gross & micro border definition: |
at least focally blurred/faded; poor circumscription
(individual melanocytes peripheral to nests/theques) |
| melanocytic atypia: |
non-typical cytology expressed as nuclear hyperchromia and
variability in small or large round cells, ovoid, spindled, or polygonal
cells; nuclear enlargement; confluent atypia2...groups of individual atypical cells...pushes toward MIS. |
| cellular cohesion, lateral: |
failing...as increased numbers of single, atypical melanocytes
are found, in some foci predominating over nests |
| cellular cohesion, vertical: |
scatter of melanocytes into superficial reaches of epidermis. Is it a primary lesion or a skin metastasis? Pathologists!!...be careful that you check history because melanoma mets can invade the epidermis in a quasi-pagetoid fashion & fool you [S08-6818]! |
| orderliness, lateral: |
clusters/theques not equidistant |
| orderliness, cluster size: |
clusters/theques not regular in size |
| orderliness, cluster shapes: |
clusters/theques become irregular in shape |
| orderliness, discreteness of clusters: |
clusters/theques fuse, becoming confluent |
| deep maturation: |
failure of nuclei to become smaller in deeper dermal aspects |
| melanin: |
distribution within lesion disorderly |
| adnexal component: |
far-down extension of atypical melanocytes |
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inflammation:
| asymmetrical presence of inflammatory cells under lesion
base |
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II. Melanoma: mature/benign cells vs. small melanoma cells
MAJOR
CRITERIA:
| mature melanocytic nevus cells: |
small cells of malignant melanoma: |
| typical nuclei |
atypical nuclei |
| no or inconspicuous nucleoli |
prominent nucleoli |
| monomorphic nuclei |
pleomorphic nuclei |
| nuclei 7-10 microns (RBC=7) |
nuclei sometimes >10 |
| amitotic; Ki67 not elevated [S08-7118] |
occasional mitoses; elevated Ki67 |
| no necrotic cells |
occasional necrotic cells |
| no plasma cells @ lesion base |
plasmas @ base, occasionally |
| no continuity with overlying melanoma cells |
continuity with overlying melanoma cells |
| nests @ lesion base, when present, small and smooth
bordered |
nests @ lesion base, when present, are large and have
irregular borders |
| nests become progressively smaller as deeper in skin |
nests become progressively larger as deeper in
skin |
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II. Melanoma: mature/benign cells vs. small melanoma cells
MINOR
CRITERIA:
| mature melanocytic nevus cells: |
small cells of malignant melanoma: |
| little or no pigment in base of lesion |
abundant pigment at base of lesion, often |
| angiocentric & periadnexal arrangement, often |
no angiocentric & periadnexal arrangement |
| solitary cellular units in reticular dermis |
cells rather in discrete nests in reticular dermis |
| scant discernible cytoplasm in cells at lesion base |
discernible cytoplasm in some cells at lesion base |
| delicate fibrillary collagen between individual cells |
no delicate fibrillary collagen between individual
cells |
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[pigmented lesions/melanoma] [defined:
levels, growth phases, etc.]
References:
- Maize JC, Ackerman AB, Pigmented Lesions of The Skin [text],
1987 (EJM's office)
- McKee, Calonje, & Granter, Pathology of The Skin...
(posted 2001; latest addition 8 August 2008) |
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1999 - 2006, all rights reserved, Pathology Associates Of Lexington,
P.A. |
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