Ch19 Atyp FP vs Desmoplastic
Melanoma
F5247fibpap010

F1Ch19 (F5274): This small lesion is slightly polypoid. The epidermis is thin with patterns of liquefaction degeneration at the dermal-epidermal interface; there is hyperkeratosis. An abormal fibrous matrix presses upon the thin epidermis. It is slightly hyper-cellular near the D-E interface. the pattern of collagen bundles is abnormal and, focally, coarse collagen bundles are arranged in stacks, mostly in a direction that parallels the epidermis. Vessels are ectatic.

F5247fibpap020

F2Ch19 (F5247): The epidermis mostly has the characteristics of a thin superficial unit, in patterns that correlate with a damaged, mostly deficient basal unit. the granular layer is prominent. Many of the cells in the dermis near the D-E interface are stellate in outline (a dendritic quality); these cells show some variability in nuclear size and staining. There are numerous dendritic melanophages. Vessels are ectatic.

Buster (the plight of feral cats)

F5247fibpap060

F3Ch19 (F5247): Near a margin on the left, both a basal unit and a superficial unit are represented; the granular layer is prominent. There is melanocytic hyperplasia (an increased number of clear cells). Collagen bundles are coarse, wavy, and hyalinized. A division that might be characterized as papillary dermis is not represented. There are scattered melanophages. Vessels are ectatic. There is perifollicular fibrosis.

F5247fibpap070

F4Ch19 (F5247): The advanced patterns somewhat obscure the patterns of collagen bundles but they are sufficiently represented to be characterized as being of a type seen in the setting of fibrous papule. Some of the coarse, vertically oriented bundles extend to the D-E interface. Dendritic firboblastic cells of the dermis show variations in nuclear size and staining. The epidermal changes are of a type commonly seen in lesions of fibrous papules; there is liquefactin degeneration at the dermal-epidermal interface. There is melanocytic hyperplasia and some of the melanocytic cells are cytologically atypical. Some of the basal unit keratinocytes are individually enlarged and dyskeratotic.

F5247fibpap080

F5Ch19 (F5247): In enlarged lacunae and in small, rounded lytic defects in the basal unit of the epidermis, there are atypical dendritic cells that resemble atypical melanocytes. In addition, a defect to the right contains dendritic cells and necrotic keratinocytes; some of the dendritic cells are acceptable as examples of dendritic histiocytes (Langerhans cells). The abnormal matrix extends to the D-E interface. There are scattered melanophages.

F5247fibpap090

F6Ch19 (F5247): Melanocytes are increased in number in the basal layer of the epidermis. Keratinocytes at the D-E interface are dyskeratotic. The patterns at the D-E junction are those of a cell-poor lichenoid reaction. Yellow arrows identify a defect containing loosely spaced dendritic cells; these cells show some degree of variability in nuclear characteristics.

F5247fibpap100

F7Ch19 (F5247): There is melanocytic hyperplasia. The loosely clustered dendritic cells in the defect on the left (yellow arrows) are difficult to characterize as to type in the absence of immunohistochemical reactions. The pattern of collagen bundles in the dermis is characteristic, and a vessel is outlined by concentric lamellae. There is some degree of atypia in the population of clear cells in the epidermis; there is a mild to moderate melanocytic dysplasia.

BuiltWithNOF

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