Clinical communication — Kliniese mededeling Multiple eyelid apocrine hidrocystoma in a domestic short-haired cat

INTRODUCTION Tumour and tumour-like lesions of the eyelids are more common in dogs than cats. In the feline, malignant tumours outnumber benign types, with eyelid neoplasms essentially arising from the haired skin. Based on 1 study, squamous cell carcinomas, fibrosarcomas and adenocarcinomas constitute 73.5 % of all feline eyelid tumours. Apocrine hidrocystomas in cats are rare, solitary and most often occur in the skin of the head, pinna, neck and axilla, limbs and tail. All variants of apocrine sweat gland tumours constitute 3 % of feline skin tumours. The term apocrine cystadenoma is a more accurate designation and is synonymous with apocrine hidrocystoma which is one of many types of apocrine sweat gland tumours. Although apocrine sweat glands exist within the skin of the eyelid and the eyelid margin, where they are called glands of Moll, apocrine sweat gland tumours in this location are uncommon in small animals. Multiple cystic lesions originating from apocrine sweat glands and resembling apocrine hidrocystomas of humans have been described in 2 separate papers involving eyelids of 5 Persian cats and 1 Himalayan cat. CASE HISTORY A 12-year-old, black, neutered, female domestic short-hair cat was referred for evaluation of slowly enlarging, multiple periocular masses around the left eye of 12 months’ duration. An excisional biopsy of a similar cystic lesion on the mid tail and left upper eyelid were performed by the referring veterinarian. The histopathology report confirmed benign, apocrine cystadenoma. On ophthalmic examination, multiple, soft and firm, locally extensive, pigmented nodules were found on the upper and lower palpebral margin, with smaller nodules extending caudally on the head and around the base of the left ear (Fig. 1). The lesions were nonpruritic, nonpainful, with no evidence or history of self mutilation/trauma with the exception of the lesions on the tail, which was previously amputated. The nodules were measured using callipers and were 3–15 mm in diameter extending dorsally from the medial canthus and around the lateral canthus to the mid-ventral palpebral margin (Fig. 2). The skin overlying the nodules was thin, pigmented and alopecic. The referring veterinarian had previously amputated the tail, based on poor response after surgical lancing and wound management. The nodules previously described on the tail appeared to have a similar presentation to the eyelid margin nodules. No other ophthalmic abnormalities were noted. Eyelid melanoma and mast cell tumour were considered as possible differential diagnosis based on pigmentation and location. Thoracic radiographs performed ruled out the possibility of metastasis. Fine-needle aspirates of the nodules were not taken during our evaluation based on previously published reports showing poor correlation of diagnostic cytology for apocrine hidrocystomas. A tentative diagnosis for apocrine hidrocystoma was made based on the previous biopsy report