Orbital invasive squamous cell carcinoma with adnexal involvement clinically mimicking feline restrictive orbital myofibroblastic sarcoma: 19 cases (1990-2016).

OBJECTIVE: To describe the clinical presentations of patients diagnosed with ocular adnexal or orbital squamous cell carcinoma (SCC), which possess features similar to feline restrictive orbital myofibroblastic sarcoma (FROMS). PROCEDURES: A retrospective review of adnexal and/or orbital SCC was performed. Cases were collected from the University of Georgia College of Veterinary Medicine and the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) (1990-2016). Data included signalment, ophthalmic clinical signs, nonophthalmic history and clinical signs, clinician suspicion of FROMS, advanced imaging results, and subsequent histopathologic diagnosis. FROMS cases from the COPLOW over the same time span were reviewed and compared statistically to the SCC cases with a significance threshold of 0.05. RESULTS: Nineteen cases (20 eyes) were identified with adnexal SCC with features similar to FROMS, including keratitis and eyelid/third eyelid restriction and/or thickening. There were no statistically significant differences between clinical findings in the SCC cases and the identified and compared FROMS cases (57 cases; 67 eyes), except for exophthalmos and/or resistance to retropulsion, which was less common in SCC cases (20%) than in FROMS cases (47.8%) (P = 0.027); and clinical or imaged presence of an overt eyelid or orbital mass, which was more common in the SCC cases (30%) than in the FROMS cases (4.5%) (P = 0.0010). CONCLUSIONS: SCC with adnexal involvement has many features similar to FROMS. In addition to FROMS, SCC should be considered a differential diagnosis in cats with restrictive adnexal or orbital signs and corneal changes.

Bilateral obturator neuropathy caused by an intrapelvic fibrosarcoma with myofibroblastic features in a dog.

A nine-year-old female Rottweiler presented with a 6-week history of progressive impairment of hindlimb adduction. Clinical examination showed abduction of both hind legs when walking on a smooth surface, pain at the medial surface of the left thigh, and an intrarectal palpable mass at the pelvic floor. Electromyography demonstrated fibrillation potentials in the adductor muscles on both sides. Pelvic radiographs showed severe osteolysis of the ischium. Gross post-mortem examination following euthanasia disclosed a large retroperitoneal mass, invading the obturator foramina and compressing both obturator nerves. Histopathological examination revealed a high-grade anaplastic sarcoma. Immunohistochemically, the tumour cells labelled positively for vimentin and alpha-smooth muscle actin, hence the tumour was considered a "myofibroblastic fibrosarcoma". This unique case report describes a novel cause of obturator neuropathy in veterinary medicine. To date, clinical descriptions of obturator nerve lesions have been limited to pelvic fractures in small animals and following difficult labour in large animals.

Disseminated pleomorphic myofibrosarcoma in a grizzly bear (Ursus arctos horribilis).

The pathological and diagnostic features of a widely disseminated pleomorphic high-grade myofibroblastic sarcoma are described in a 23-year-old male brown bear (Ursus arctos horribilis). Firm, solid, white to tan neoplastic nodules, often with cavitated or soft grey-red necrotic centres, were observed throughout most internal organs, subcutaneous tissues and skeletal muscles on gross examination. Microscopically, the tumour consisted of pleomorphic spindle cells forming interlacing fascicles with a focal storiform pattern with large numbers of bizarre polygonal multinucleate cells, frequently within a collagenous stroma. Immunohistochemistry, Masson's trichrome stain and transmission electron microscopy designated the myofibroblast as the cell of origin. This is the first case of a high-grade myofibrosarcoma in a grizzly bear.

Low-grade myofibroblastic sarcoma of the maxillary region in a dog.

A subcutaneous tumour was identified in the maxillary region of a 14-year-old mixed breed dog. This tumour had grown rapidly over 2 weeks. Microscopically, the tumour had ill-defined borders and was composed of bundles and whorls of atypical spindle cells accompanied by abundant collagen fibres. Immunohistochemically, neoplastic cells were immunoreactive for vimentin, α-smooth muscle actin and calponin and negative for S100 protein, von Willebrand factor, desmin and smoothelin. These results suggested that the neoplastic cells were derived from myofibroblasts and that the tumour was a low-grade myofibroblastic sarcoma.