October 2016



Signalment (Slide A - JPC 2785784):  Miniature schnauzer

HISTORY:  Firm, pedunculated dermal mass

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Expanding the dermis and elevating the overlying hyperplastic and focally ulcerated epidermis is an unencapsulated, pedunculated, moderately cellular neoplasm composed of spindle cells arranged in short, interlacing streams and bundles, separated by moderate amounts of collagenous matrix.  Neoplastic cells have indistinct cell borders, moderate amounts of eosinophilic cytoplasm that occasionally contains brown pigment globules (melanin), an oval to elongate nucleus with finely stippled chromatin and one variably distinct nucleolus.  There is mild anisocytosis and anisokaryosis and mitotic rate is 1 per 10 HPF.  Multifocally, there are individual or small nests of neoplastic cells within the epidermis (junctional activity).  Multifocally, within the dermis, there are scattered macrophages with intracytoplasmic melanin (melanomacrophages). The epidermis is focally ulcerated with an overlying serocellular crust composed of cellular debris, degenerate neutrophils, hemorrhage, fibrin, and colonies of basophilic cocci.  Subadjacent to the crust within the superficial dermis there are increased numbers of small caliber blood vessels lined by reactive endothelium that are perpendicular to the ulcer, surrounded by abundant hypertrophied fibroblasts (granulation tissue).  Rare apocrine glands are ectatic and surrounded by moderate numbers of lymphocytes, plasma cells and fewer transmigrating neutrophils and macrophages (hydradenitis).  The remaining epidermis is moderately hyperplastic, with acanthosis, spongiosis, and rete ridge formation.

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Melanocytoma, miniature schnauzer, canine.

Signalment (Slide B - JPC 2327682):  Age and breed unspecified dog.

HISTORY:  A mass on the digit

HISTOPATHOLOGIC DESCRIPTION:  Haired skin and bone, digit:  Expanding the dermis, elevating a focally extensively ulcerated epidermis and infiltrating the bone of P3 is a moderately cellular infiltrative neoplasm composed of polygonal to spindle cells arranged in lobules, nests, and packets supported by moderate amounts of fibrovascular stroma.  Neoplastic cells have variably distinct cell borders, scant to moderate amount of eosinophilic granular cytoplasm that often contains brown pigment globules (melanin), a round to oval nucleus with finely stippled chromatin and one to two prominent nucleoli.  There is moderate anisocytosis and anisokaryosis.  Mitotic rate averages 2-3 per HPF.  Multifocally, there are individual or small nests of neoplastic cells within the hair follicular epithelium (junctional activity).  There is single cell necrosis within the neoplasm moderate numbers of melanomacrophages as well as large multifocal areas of necrosis with hemorrhage, fibrin, edema, moderate numbers of viable and degenerate neutrophils, and fewer hemosiderin-laden macrophages.  There is multifocal bone loss and replacement by neoplastic cells (osteolysis). There are often scalloped trabeculae of woven bone extending from the remaining mature bone and osteoclasts within Howship’s lacunae (bony remodeling). 

MORPHOLOGIC DIAGNOSIS:  Haired skin and bone, digit:  Melanoma, breed unspecified, canine.









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