Ch17 Atyp Fibrous 

F1Ch17 (K1574): A fibrous lesion abuts directly upon the epidermis. To the right, the epidermis shows slightly elongated rete ridges. Over the remainder of the lesion, the epidermis shows effacement of the rete ridges and liquefaction degeneration at the dermal-epidermal interface. A papillary dermis cannot be identified in the area of this small tumor.The fibrous tissue of the lesion is hyper-cellular; most of the cells are interpreted as fibrocytes. Vessels are increased in number and ectatic. Just to the right of the center of the field, loosely spaced collagen bundels are coarsened and acidophilic; they form parallel arrays. The interface with the reticular dermis is not sharply defined.


Buster (the plight of feral cats)

F2Ch17 (K1574): In this field, the epidermis shows effacement of the rete patterns with liquefaction degeneration at the dermal-epidermal junction. A basal unit is not represented; the epidermis consists of a superficial unit. There is hypergranulosis and compact hyperkeratosis. To the left, the epidermis is atrophic. Vessels are ectatic.


F3Ch17 (K1574): Duplicated basement membranes outline clusters of epithelioid cells (blue arrows). The degree of cellularity is greater than that seen in the usual fibrous papule.

Small lytic defects at the dermal-epidermal junction contain loose collections of fibrin. The lesion is hyper-cellular; near the dermal-epidermal interface, there are small clusters of epithelioid cells and individually isolated epithelioid cells. Some of these cells are multi-nucleated. Throughout the lesion, there are scattered    multi-nucleated giant cells. Vessels are ectatic and there is some degree of     peri-vascular hyalinization. Small collagen bundles are arranged in complex patterns.


F4Ch17 (K1574): The epidermal changes are of a type that can be seen as a regional variation in a fibrous papule. There is lysis of the basal layer of keratinocytes. Green arrows identify membranous acidophilic deposits about clusters of atypical epithelioid cells; some of the atypical cells are multi-nucleated. The basement membrane-like material might be compared to the membranous loops of a fibrous papule, but membranous fibrin deposits should also be considered. Some to the cells have prominent nucleoli. Less acidophilic membranous deposits are present about individual cells and small clusters of cells in the lower 1/2 of the field. Vessels are ectatic.


F6Ch17 (K1574): A follicle, cut in cross-section, shows melanocytic hyperplasia. Some of the melanocytes have enlarged nuclei with prominent nucleoli. The widened, delicately fibrotic sheath contains an loose infiltrate of lymphocytes and histiocytes (continued as chapter 18).


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