Malignant melanoma

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).

Notes:

Can look almost like anything.
- Like it is said that sarcoidosis is in every internal medicine DDx... melanoma is every pathologic DDx.

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.

Breslow thickness

Depth measured from stratum granulosum to deepest intradermal tumour cell - predictive of survival.^[1]

Electron microscopy

Melanosomes.

Image(s):

Melanosomes (nature.com).

Stains

Fontana-Masson stain, stains melanin.^[2]
- 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.^[3]
- 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.

References

↑ Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 595. ISBN 978-1416054542.
↑ 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.

[1] Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 595. ISBN 978-1416054542.

[2] URL: http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exfontana.htm. Accessed on: 5 May 2010.

[pmid20653825-3] 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.

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Malignant melanoma

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