Hibernomas are uncommon benign tumors of brown fat that occur in humans and various animal species. They have not been observed in the orbit of dogs, humans, or other animals. Here we report clinical, light and electron microscopic, and immunohistochemical features of a series of 7 hibernomas arising in the orbital region of dogs. These neoplasms occurred in adult dogs with no breed predilection. The mean age of the affected dogs was 10.4 years (range, 8-13 years). All neoplasms presented as soft lobular masses composed of predominantly round or polygonal neoplastic cells with granular eosinophilic and vacuolated cytoplasm resembling adipocytes. The cytoplasm contained large numbers of pleomorphic mitochondria with dense matrices and indistinct cristae. Immunohistochemical evaluation confirmed positive labeling of neoplastic cells from all cases with uncoupling protein 1 (UCP-1) consistent with brown fat differentiation. Interestingly, rare neoplastic cells also expressed myogenin and myoD, possibly suggesting a common progenitor cell for neoplastic brown adipose and skeletal muscle cells.

A previously healthy, adult male blue crane (Anthropoides paradiseus) became peracutely distressed and ataxic. Examination revealed hemoptysis and a large mass associated with the cranial aspect of the sternum (keel). The patient died before treatment could be initiated. Gross necropsy revealed a large, hemorrhagic mass originating from the cranial aspect of the keel and extending into the cranial coelomic cavity. Histopathology confirmed the mass as an osteosarcoma. This is the first known report of an osteosarcoma in any crane species.