Apocrine Hidrocystoma in Four Persian Cats

This case series describes four cats, tentatively diagnosed with eyelid apocrine hidrocystoma (AH), a relatively uncommon benign tumor of Moll's glands. All four were Persians, middle-aged or older (median age 7 years; range 4-11 years). In all cats, lesions initially appeared near the medial canthus as dark, round, fluid-filled, non-painful masses of variable size (1-10 mm) and number (up to 20 per cat). No discomfort was observed. In three cases, cyst-like lesions were aspirated for therapeutic or diagnostic reasons, yielding a dark-brown to black turbid fluid, which was examined microscopically in three cases. In two, cytology showed reactive macrophages, with intensive phagocytosis of black-colored debris. In one case, cytology showed numerous cholesterol clefts. Fine needle aspiration of AH allows differentiation of AH, a benign tumor, from other, potentially malignant eyelid lesions (e. g. melanoma). In addition, aspiration and drainage of the lesion content reduces mass size, and therefore has a temporary therapeutic effect. Although a definitive diagnosis of AH is based on histopathology of tissue biopsies, we believe that the signalment, history, the macroscopic appearance and location and the cytological findings of the lesions were highly suggestive of AH.