Conceição et al; Cutaneous nodular fasciitis in the dog. Morphological and immunohistochemical study. Braz J Vet Pathol, 2009, 2(1), 41 - 44 Brazilian Journal of Veterinary Pathology. www.bjvp.org.br . All rights reserved 2007. 41 Case report Cutaneous nodular fasciitis in the dog. Morphological and immunohistochemical study Lissandro G. Conceição 1 , Livia M. R. Acha 1 , Jose C. L. Moreira 1 , Fabricia H. Loures 1 , Lucia M. R. Silveira 2 , Renee L. Amorim 3 , Rafael T. Neto 3 1 Departamento de Veterinária, Universidade Federal de Viçosa, Viçosa, MG, Brazil. 2 Clinician, Private Practice, São Paulo, SP, Brazil. 3 Departamento de Clínica Veterinária, Faculdade de Medicina Veterinária e Zootecnia, Botucatu, Universidade Estadual Paulista, Unesp, SP, Brazil. *Corresponding author: Lissandro G. Conceição – Departamento de Veterinária, Universidade Federal de Viçosa, campus universitário s/n. Viçosa - MG. CEP: 36570-000. Phone: 55 31 3899 1441 / 2317. E-mail: lissandro@ufv.br Submitted November 13 th 2008, Accepted February 10 th 2009 Abstract Nodular fasciitis is a benign soft tissue lesion commonly diagnosed in human beings, but with rare description in dogs and cats. A female, spayed, 7.5 years old, otherwise healthy Labrador was examined because of a nodular growth of rapid development in the infraorbital region. The histopathological examination from the excisional biopsy revealed a well circumscribed proliferation of plump and moderately pleomorphic fibroblasts and vascular proliferation with a small central area of degeneration. Nodular fasciitis was diagnosed and several months pos surgical excision, no recurrence was observed. This report illustrates an histologically well circumscribed lesion of cutaneous nodular fasciitis in a dog, similar to some lesions in human beings and different from what is usually reported in veterinary patients. Key Words: Nodular fasciitis, vimentin, cytokeratin, GFAP, S100, dog. Introduction Nodular fasciitis (NF), first described in human medicine as subcutaneous pseudosarcomatous fibromatosis (11), and also known as pseudosarcomatous fasciitis, is considered a benign, reactive lesion (8, 11), well described in human dermatology, but poorly reported in dogs and cats in scientific papers (3, 10). NF in humans is perhaps the mesenchymal neoplasm that is most often misdiagnosed as a sarcomatous lesion, due to its fast growth and histological aspect (11). When described in dogs, NF is related mainly with ophthalmic lesions (1, 4). Information on cutaneous NF in dogs is restricted to a few textbooks (3, 6, 10). The purpose of this article is to describe the morphological and clinical findings of NF in a dog. Case Report A 7.5 year old, female, spayed, yellow Labrador was presented with the main complaint of a facial growth of rapid development (two weeks) localized in the infraorbital region. According to the owner, no known trauma had occurred; however, this possibility could not be ruled out due to history intense physical activity of the animal. Physical examination showed an otherwise healthy dog with a one centimeter painless firm mass slightly adhered to the deep tissue covered by a normal skin appearance. Complete blood cell count, urinalysis, biochemical profile, chest X-rays, abdominal ultrasound, electrocardiogram and echocardiogram showed no abnormalities.