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.
(© 2017 American College of Veterinary Ophthalmologists.)