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

Abstract

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.

What Is Your Diagnosis?

“…1,2 This condition most commonly affects middle-aged to older cats without an apparent sex or breed predisposition. 2,3 Typical ocular examination findings of cats with FROMS include eyelid thickening, restricted eyelid mobility, decreased retropulsion of the globe, and exposure keratitis. [1][2][3] The disease is initially unilateral and can commonly extend to the contralateral eye, the oral cavity, and other facial tissues.…”

“…2,3 Typical ocular examination findings of cats with FROMS include eyelid thickening, restricted eyelid mobility, decreased retropulsion of the globe, and exposure keratitis. [1][2][3] The disease is initially unilateral and can commonly extend to the contralateral eye, the oral cavity, and other facial tissues. 1,2 Bone involvement has been described in cases of FROMS, ranging from sclerosis and erosion to extensive and aggressive osteolysis.…”

“…FROMS can be a clinical diagnostic challenge, with other tumors such as SCC with adnexal involvement having similar clinical and imaging features. 3 Differentiation of these tumor types is important, as therapeutic options and outcomes are variable. Cats with FROMS more commonly exhibit exophthalmos and/or resistance to retropulsion compared to cats with SCC, and the presence of an overt eyelid or orbital mass on examination or diagnostic imaging is more common in cats with SCC than FROMS.…”

“…Cats with FROMS more commonly exhibit exophthalmos and/or resistance to retropulsion compared to cats with SCC, and the presence of an overt eyelid or orbital mass on examination or diagnostic imaging is more common in cats with SCC than FROMS. 3 Histopathologic evaluation can readily differentiate SCC from FROMS. 3 SCC is characterized by invasive islands, cords, and trabeculae of variably pleomorphic epithelial cells, whereas FROMS appears as a highly infiltrative population of bland spindle cells with moderate collagen deposition and low mitotic index.…”

“…3 Histopathologic evaluation can readily differentiate SCC from FROMS. 3 SCC is characterized by invasive islands, cords, and trabeculae of variably pleomorphic epithelial cells, whereas FROMS appears as a highly infiltrative population of bland spindle cells with moderate collagen deposition and low mitotic index. 1,2,4 The neoplastic entity of FROMS spreads along fascial planes and encircles preexisting tissues, causing atrophy of entrapped skeletal muscle and peripheral nerves, 2 as was noted histologically in this case.…”