title: Distinctive unclassified mesenchymal tumor of the digit of dogs.
abstract: Four examples of a mesenchymal tumor of undetermined histogenesis occurred in three mixed-breed dogs and one Yorkshire terrier. All tumors occurred as solitary, soft to firm, solid, tan, and ulcerated masses in the digits of dogs aged 11 to 15 years. The compact cellular tumor had cells with anisokaryotic round, oval, or irregular nuclei, some of which were multinucleated. The neoplastic cells appeared to arise in the tissue near the third phalanx in the area of dense collagenous trabeculae located proximal to the fat pad and sweat glands. The unclassifiable cells had some features of histiocytes by transmission electron microscopy, but failed to stain for lysozyme and alpha-1-antichymotrypsin, markers for monocyte-macrophage derived cells. Immunohistochemically, the cells stained for vimentin but not for cytokeratins, desmin, S-100 protein, epithelial membrane antigen, alpha-lactalbumin, lysozyme, alpha-1-antichymotrypsin, alpha-lactalbumin, casein, and heavy and light chain immunoglobulins. The combined findings of light and transmission electron microscopy and immunohistochemistry exclude tumor histogenesis from an epithelial cell, melanocyte, mast cell, plasma cell, Schwann cells, and Merkel cell.
authors.affiliation: Department of Pathology, Angell Memorial Animal Hospital, Boston, MA.
authors.forename: J L
authors.initials: JL
authors.lastname: Carpenter
authors.forename: Y
authors.initials: Y
authors.lastname: Dayal
authors.forename: N W
authors.initials: NW
authors.lastname: King
authors.forename: F M
authors.initials: FM
authors.lastname: Moore
mesh_terms: D000818:Animals; D004283:Dog Diseases / Q000473:pathology*; D004285:Dogs; D005260:Female; D005534:Foot Diseases / Q000473:pathology / Q000662:veterinary*; D007150:Immunohistochemistry; D008297:Male; D008637:Mesenchymoma / Q000473:pathology / Q000648:ultrastructure / Q000662:veterinary*; D008854:Microscopy, Electron; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000473:pathology / Q000648:ultrastructure / Q000662:veterinary*