Equine Sarcoid Arising From the Medial Caruncle With Invasion of the Third Eyelid in a Quarter Horse Gelding.

Equine sarcoids should be considered for medial caruncle/third eyelid masses; excision with cryotherapy is effective.

This case report describes the first documented presentation of an equine sarcoid originating from the medial caruncle with subsequent invasion of the third eyelid in a 20-year-old Quarter Horse gelding. Initial incisional biopsy of the medial caruncle mass revealed spindle cell neoplasm characteristics, after which rapid tumor growth occurred affecting the third eyelid and adjacent superior palpebral conjunctiva. Definitive treatment involved complete third eyelid and medial caruncle excision with resection of affected palpebral conjunctiva followed by adjunctive cryotherapy. Histopathologic examination confirmed equine sarcoid diagnosis through identification of densely cellular neoplastic spindle cells arranged in interlacing bundles with collagenous stroma and hyperplastic overlying epithelium. Molecular analysis revealed strong hybridization signaling for bovine papillomavirus types 1 and 2 in over 90% of neoplastic cells, confirming the viral etiology. This case highlights the importance of considering sarcoids in differential diagnoses for medial caruncle and third eyelid masses in horses. The authors emphasize that rapid tumor growth following incisional biopsy, commonly observed with cutaneous sarcoids, may similarly occur with medial caruncle or third eyelid-derived sarcoids.

This summary was distilled by AI and may occasionally misinterpret data. Confirm critical details with the primary literature before clinical application.