Histology of Melanoma

Contributed by Irma Gimenez-Conti, Steven Kazianis, Rodney Nairn, Ronald Walter, and Don Morizot

Kazianis, S., Gimenez-Conti, I., Trono, D., Pedroza, A., Chovanec, L., Morizot, D.C., Nairn, R.S., and R.B. Walter (2001) "Genetic Analysis of MNU-Induced Neoplasia within Xiphophorus Hybrid Fish." Marine Biotechnology 3(S1): 37-44.

Melanotic Hyperpigmentation

Cross section of the caudal peduncle showing hyperpigmentation restricted to the integument (70 x).

Pre-cancerous Melanosis

Fish skin showing aggregations of pigmented cells along the skin-dermis junction, around the scales, but sparse in the dermis (175 x).

Melanocytic Melanoma

This exophytic tumor shows the penetration of melanocytes into the dermis but the lack of invasiveness into the underlying muscle tissue.

Melanotic Melanoma

A higher magnification showing the predominant type of tumor cell, dendritic or spindle shaped. Their nuclei are oval and regular, and some cells are heavily pigmented (250 x).

Spindle Cell Type Melanoma

This tumor shows heavily pigmented spindle cells (175 x).

Spindle Cell Type Melanoma

Higher magnification showing fusiform cells with elongated nuclei and abundant melanin in the cytoplasm (500 x).

Epithelioid Cell Type Melanoma

Exophytic growth composed mostly of epithelioid cell types. Blood vessels are sparse throughout the whole tumor (70 x).

Epithelioid-Cell Type Melanoma

Higher magnification shows cuboidal-shaped cells with oval nuclei and dusty cytoplasmic melanin pigment (1000 x).

Melanophore-Macromelanophores

Polymorphic Melanoma

Cross section of a heavily pigmented tumor. Pigmented cells are invading the musculature (70 x).

Amelanotic Melanoma

This tumor is located entirely in the dermis and do not invade the musculature. Most cells do not contain melanin, but in some small areas that are lightly pigmented cells (125 x).