History: A 4-year-old male entire blonde Labrador Retriever with a history of left ocular abnormalities, Horner syndrome accompanied by neurological signs (star gazing, lethargy, hind limb weakness, pacing).
Histopathological description: Left eye. A focal, round, well-defined multilobulated, moderately cellular mass composed of plump haphazardly arranged spindle shaped cells and varying amounts of chondromatous matrix extends from the pigmented epithelium of the choroid, elevating and detaching the overlying retina which is folded and protrudes in the posterior chamber. In areas of cartilaginous differentiation single or pairs of neoplastic cells fill lacunae. The cells have a moderate amount of finely granular eosinophilic to basophilic cytoplasm, a large oval nucleus and finely stippled chromatin with 1-2 prominent nucleoli. The mitotic count is high. Anisocytosis and anisocytosis are marked with occasional binucleate or multinucleate cells.
MD: Intraocular metastatic chondrosarcoma
Final comment: Post-mortem examination revealed the presence of masses in the rib, lung, kidneys, spleen, lymph nodes and both eyes. The main differential diagnosis in this case would be chondroblastic osteosarcoma as some of the eosinophilic matrix produced by the neoplastic cells resembles osteoid. The rib as primary neoplasm location and the lack of bone formation in all sections examined are more suggestive of chondrosarcoma. The malignancy of the neoplasm in this case is striking with the high mitotic rate and the large proportion of undifferentiated spindle shaped cells in the metastases. Intraocular metastasis would be a rare finding.
Contributors: Ilaria Piras DVM, PhD; Hanne Jahns DVM, PhD, Dipl. ECVP; Peter O’Brien DVM, PhD, FRCVS, Dipl ECVCP, Dipl ACVP; Pathobiology Section University College Dublin Veterinary Hospital.
References
Thompson KG, Dittmer KE. Tumors of Bone. In: Tumors in Domestic Animals. 2016:356-424