Cutaneous mast cell tumor in a Mixed-breed dog: A case report

Background: Mast cell tumor is one of the most common cutaneous neoplasms in dogs, originating from mast cells. Although it can occur in various body sites, its manifestation as a visible eyelid mass is relatively uncommon. Mast cell tumors may be accompanied by inflammatory reactions, particularly suppurative inflammation, which can complicate early diagnosis. Clinical signs may include redness, swelling, pruritus, discharge, pain, or eyelid deformity. Fine needle aspiration (FNA) cytology is considered the most reliable diagnostic tool for confirmation. This report describes a case of eyelid mast cell tumor associated with suppurative inflammation in a dog. Methods: In April ۲۰۲۵, a ۷-year-old male mixed-breed dog was presented with a red, firm, elevated mass on the upper eyelid of the right eye. FNA sampling was performed, and smears were stained using Giemsa for cytological evaluation. Results: Clinical examination revealed a solitary, reddish, semi-firm mass approximately ۸ mm in diameter, intermittently pruritic but without evident pain or discharge. Cytological evaluation showed abundant round cells with distinct cytoplasmic borders, eosinophilic cytoplasm, and large pale atypical nuclei. The background contained necrotic areas, intercellular edema, and heavy infiltration of neutrophils and inflammatory cells. These findings were consistent with mast cell tumor associated with suppurative inflammation and necrosis. For diagnostic confirmation, immunohistochemistry using the c-KIT (CD۱۱۷) marker was performed, which showed positive expression in the neoplastic cells and confirmed the diagnosis of mast cell tumor. Conclusion: Although mast cell tumors are relatively common in dogs, their occurrence in the eyelid is rare and can present diagnostic challenges due to concurrent inflammatory reactions. Accurate cytological assessment is crucial for differentiation. Middle age, male sex, and certain breeds are recognized predisposing factors, consistent with the present case. Surgical excision with margin evaluation remains the primary treatment, while concurrent anti-inflammatory management and regular follow-up are recommended for improved prognosis. Although fine needle aspiration (FNA) cytology and immunohistochemistry (ICC) provide valuable diagnostic information, histopathology remains the gold standard for determining tumor type, predicting prognosis. The present report did not include complete histopathological assessment, which should be considered a limitation of this study.

کلیدواژه ها:

Eyelid neoplasm ، Mast cell tumor ، Canine cytology ، Suppurative inflammation