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1. Histopathology of Inflammation

2. Minimal Deviation Melanoma, etc.

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F1Ch44 (R5748): This expansile lesion is carcinoma. To the left of the nodule, an intraepithelial process is represented; in this area, there is acanthosis, hyperkeratosis, and papillomatosis. The tumor nodule is smoothly expansile at its interface with the dermis. Within the nodule, fascicles of tumor cells are closely aggregated. The tumor is ulcerated.

f2Ch44: Atypia is not as marked in the intraepithelial component (yellow arrows) as in the nodule. The intraepithelial component is associated with a band-like infiltrate of lymphoid cells.

F3Ch44: The epithelial component has pushed into the dermis. Atypia is moderately severe. Blue arrows identify an isolated nests of atypical squamous cells in a pattern of microinvasive carcinoma.

F4Ch44: Atypical, pale cells form closely spaced fascicles; each fascicle is outlined by an acidophilic membrane. Tumor stroma is scanty. The tumor is smoothly expansile at its interface with the dermis.

F5Ch44: This tumor cytologically is a high-grade carcinoma. The tumor cells have pale cytoplasm, and enlarged nuclei with marginated chromatin. Nucleoli are prominent. Basement membranes are coarse and acidophilic. Red arrows identify several whorls, one of which has a central area of keratinization. Small yellow arrows point to mitotic figures. Tumor cells are somewhat spindle shaped.

F6Ch44: Focally, the tumor shows some degree of pleomorphism. There are scattered mitotic figures. Below the horizontal axis of the center of the field, on the left, there is a small cluster of mitotic figures. Some of the nests are outlined by hyaline membranes. There are scattered dyskeratotic cells.

F7Ch44: Clear cell patterns are focal in distribution; the clear cell change prominently affects the cells of the whorls.

F8Ch44: The cells, forming the whorl near the center of the field, have vacuolated cytoplasm; in addition, there are dyskeratotic features. There is some degree of nuclear pleomorphism.

This lesion is a carcinoma with marked atypia and mitotic activity. It is confined to the dermis on the available sections, but the solid character of the lesion and the uniform degree of atypia are worrisome features. Many of the histologic features can be related to features of tricholemmal differentiation. There are other options, such as clear cell squamous cell carcinoma. A metastasis should also be mentioned in the diagnosis. There are in situ patterns in the neighboring epidermis, but this feature does not entirely exclude metastatic carcinoma.