Liro71

Microscopic Description:
There is a dome-shaped biopsy of skin with a compound melanocytic neoplasm.
Melanocytes are seen focally as single cells and nests at the dermoepidermal
junction with areas of epidermal thinning and discrete areas of intraepidermal
spread. The melanocytes have amphophilic to lightly pigmented cytoplasm and
small round and oval to occasional enlarged, atypical nuclei. Similar
melanocytes are seen as crowded single cells and nests in the papillary and
upper reticular dermis, including scattered markedly pleomorphic forms. A few
superficial dermal melanocytes in mitosis are identified, as are multiple
junctional melanocytes in mitosis. The lesion extends to a radial biopsy
margin. Initial and deeper sections were examined.

Limited immunostains were performed to further evaluate this lesion.

Stain: HMB45
– Interpretation: Labels a few
junctional melanocytes; negative for dermal
component
Stain: P16
– Interpretation: Diffusely labels melanocytes

***AMENDMENT COMMENT***

This case was sent in consultation to the University of California San
Francisco Dermatopathology and Oral Pathology Service and it was interpreted
by and his diagnosis is
as follows:

Melanoma of 0.9 mm in thickness, focally involving the inked peripheral
margin.

His microscopic description, note, and tumor synoptic are as follows:

“Sections show a compound proliferation of large melanocytes with finely
pigmented cytoplasm. There are single melanocytes and irregular nests in the
epidermis with focally prominent pagetoid scatter, and there are poorly
maturing dermal melanocytes that lack dermal circumscription and can be found
in mitosis. Some cells are multinucleated. A slight lymphohistiocytic
infiltrate with admixed melanophages is noted. Expression of p16 is
maintained.

Given the cytologic atypicality, incomplete circumscription, poor maturation,
focal pagetoid scatter, and elevated dermal mitotic index that are apparent in
these slides, I believe this tumor represents a small diameter melanoma and
not a ‘melanocytic nevus of special site’. A brief synoptic is included
below.

Procedure: Shave biopsy
Microscopic tumor type: Melanoma NOS
Breslow thickness: 0.9 mm
Ulceration: Not detected
Margin: Periphery involved
Mitotic index: 2 per square millimeter
Vascular invas
ion: Not detected
Regression: Not detected
Pathologic staging (pTNM): pT1b

I agree with Dr. interpretation. The changes are sufficiently
atypical to warrant a diagnosis of melanoma.