Histiocitoma fibroso maligno en el plano nasal de un perro: Reporte de caso

Abstract

One dog, female, poodle, 8 years old, presented the main complaint of ulcerated lesion in the nasal plane, with evolution of approximately six months. The animal was submitted to anesthesia to remove the 0.5 cm diameter nodule. The material was sent for routine histopathological examination with Hematoxylin-Eosin (HE) staining and immunohistochemistry, respectively. Histopathological examination showed a nodular mass, with ill-defined edges, consisting of rounded cells of sparse cytoplasm and condensed nuclear chromatin that extended from the superficial dermis and dissected part of the epidermis. These cells had a high pleomorphism pattern and a high nucleus: cytoplasm ratio. Intermingling the stroma, a large number of vascular structures were observed, ranging from the basal surface to the superficial dermis. Immunohistochemical examination revealed strong marking for the main MHCII histocompatibility complex that strongly stains lymphocytes and histiocytes that correspond to the tumoral and proliferative structure of the tumor's neoplastic cells. Histiocytic tumors as well as histiocytomas are relatively common in young dogs and fibrous histiocytomas are more rarely diagnosed in dogs, occurring more commonly in humans. In this report, the pathological and immunohistochemical characteristics that allowed the diagnosis are described, enabling the differentiation between non-fibrotic histiocytomas and other common canine neoplasms.