Immunohistochemical diagnostic of hibernoma in dog

Nipple Hibernoma in a Dog: A Case Report With Literature Review

This report provides a clinical, histological, and immunohistochemical description of an unusual hibernoma (pale cell variant) in the subepidermal area of the nipple of a six-year-old bitch. Furthermore, an extensive literature review of hibernomas in animals was made. Physical examination revealed a nodular lesion in the subepidermal area of the third nipple of the left mammary chain. The histopathological findings included lobules of round to oval cells with abundant pale to eosinophilic cytoplasm, containing one or multiple optically empty vacuoles, consistent with nipple hibernoma. Immunohistochemically, the neoplastic cells were negative for cytokeratin AE1/AE3 and p53 but showed strong immunoreaction for vimentin and uncoupling protein-1, thus confirming the brown adipose tissue origin. Local recurrence was not detected after 18 months of follow-up. Hibernomas are rare and benign neoplastic lesions, originating from brown adipose tissue. Due to their histological and molecular resemblance with liposarcoma, a correct diagnosis of these neoplasms is required. In addition, the literature review suggests that hibernomas may present different features, according to species.

Cytologic appearance of hibernoma in two dogs

Hibernomas are rare benign tumors of brown fat (adipose tissue) that have been reported in several different species. The cytologic characterization of these tumors has not been described in dogs. In this case report, we describe two dogs with hibernomas, focusing on the cytologic appearance of these unique neoplasms. Both cytologic specimens were highly cellular and predominated by vacuolated neoplastic cells with no evidence of concurrent inflammation. The cells contained a moderate to large number of variably sized cytoplasmic vacuoles, with occasional, irregularly shaped pink granular material. Most cells contained a single nucleus; however, cells displayed moderate anisokaryosis. A biopsy with histologic examination was performed in both cases, confirming the cytologic suspicion of hibernoma. Immunohistochemistry revealed that both tumors were positive for UCP1 and vimentin, and negative for cytokeratin. Hibernoma is an important differential diagnosis in dogs with conjunctival and periocular swellings that exfoliate numerous, mildly atypical, vacuolated cells.