Squamous cell carcinoma in the orbit of a dog

By Emma Scurrell

A nine-year-old male Rottweiler presented with unilateral exophthalmos and clinical findings revealed a retrobulbar mass. Fine needle aspirates were taken from the mass and the results are shown below.

Fig 1.The smears are highly cellular and the cell population is well-preserved (modified Wrights-Giemsa, x40).
Fig 2. The dominant cell population consists of neoplastic squamous epithelial cells present singly and in small clusters. There is associated neutrophilic inflammation present (x200).
Fig 3. A closer view of the neoplastic squamous epithelial cells (x400).

Final Diagnosis

Squamous cell carcinoma (SCC)

Discussion

Squamous cell carcinomas are malignant, locally invasive neoplasms. The orbit would be a very unusual site for a primary SCC. A more common scenario is invasion of a primary sinonasal SCC through the medial orbital wall. Metastasis to the orbit from a primary SCC elsewhere is another possibility, but this is considered rare.