Malignant melanoma
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Malignant melanoma, also melanoma, is an aggressive type of skin cancer that can be diagnostically challenging for pathologists.
It fits into the larger category of melanocytic lesions which includes many benign entities, a number of which can be difficult to distinguish from melanoma.
General
- AKA Malignant melanoma.
- Main DDx: melanocytic lesions - especially if pigmented.
- Known as the great mimicker in pathology; it may look like many things.
Clinical
- ABCD = asymmetric, borders (irregular), colour (black), diameter (large).
Microscopic
Features:
- Classic appearance of melanoma:
- Loosely cohesive; mix of small nests of cells, single cells.
- Mixed of spindle and ovoid cell morphology.
- +/-Occasional large binucleated cells.
- Cytoplasm: brown pigment (melanin).
- Prominent (large) red nucleoli (like in serous carcinoma of the ovary).
- Marked nuclear pleomorphism - variation in cell size, shape & staining (like in serous carcinoma of the ovary).
- Nuclear pseudoinclusions (like in papillary thyroid carcinoma).
DDx:
- Carcinoma.
- Serous carcinoma - both serous carcinoma and melanoma have a large nucleolus.
- Sarcoma - as may have spindle cells.
- Clear cell sarcoma.
- Metaplastic carcinoma.
- Epithelioid angiosarcoma.
- Lymphoma.
- Other melanocytic lesions.
Notes:
- Can look almost like anything.
- Like it is said that sarcoidosis is in every internal medicine DDx... melanoma is every pathologic DDx.
Electron microscopy
- Melanosomes.
Image(s):
Stains
- Fontana-Masson stain, stains melanin.[1]
- May be useful to differentiate melanin from other brown stuff (e.g. lipofuscin, hemosiderin).
IHC
Standard panel:
- S-100 +ve.
- HMB-45 +ve.
- Melan A (MART-1) +ve.
Others:
- SOX10 +ve -- useful for diff. from excision scar.[2]
- SOX-10 = pan-schwannian and melanocytic marker.
Notes:
- The standard panel above (S-100, HMB-45, MART-1) is also positive in other lesions, e.g. cellular blue nevus.
See also
References
- ↑ URL: http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exfontana.htm. Accessed on: 5 May 2010.
- ↑ Ramos-Herberth FI, Karamchandani J, Kim J, Dadras SS (September 2010). "SOX10 immunostaining distinguishes desmoplastic melanoma from excision scar". J. Cutan. Pathol. 37 (9): 944–52. doi:10.1111/j.1600-0560.2010.01568.x. PMID 20653825.