M 58, left cheek.
Figs.1-4: H&E, Fig 5: S-100, Fig 6. HMB45
CLICK ON THE FIGS FOR ENLARGED VIEW
Well circumscribed dermal nodule composed of epitheliod and spindled melanocytes with large nucleoli and numerous mitotic figures.
Intracytoplasmic melanin pigment is not noted.
The neoplastic cells are strongly positive for S-100 and focally positive for HMB 45.
Overlying epidermis is raised and separated from the tumor by a clear Grenz zone.
No junctional melanoma component, epidermal pagetoid spread or ulceration.
No precursor nevoid lesion or evidence of regression.
Non-brisk dermal lymphocytic response but no lymphohistiocytic invasion.
Picture is that of a metastatic melanoma.
If no clinical or radiologic evidence of a primary melanoma is found in the patient, the lesion may be a rare subtype of melanoma called primary dermal melanoma.