[Malignant nictitating membrane tumors in dogs and cats].

Tumours of the third eyelid in 47 dogs and five cats were examined histopathologically. The clinical observations leading to the tumour diagnosis are presented. The tumours were seen more frequently in the dachshund breed, the affected cats belonged to the European Short-hair breed. The diagnosed tumours of the third eyelid could be histologically classified as adenomas and adenocarcinomas of the gland of the third eyelid, malignant melanomas, squamous cell papillomas and carcinomas of the nictitating membrane, several soft tissue tumours and some cases of pseudoneoplastic hypertrophy of the gland of the third eyelid. Local recurrence of tumour occurred in eight dogs and two cats after resection. Tumour metastasis was confirmed in three dogs. The clinical procedure recommended for avoidance of recurrence is discussed. The differential diagnosis of the malignancies of the third eyelid is described. Questionnaires were designed for the animal owners in an attempt to identify etiopathogenetically important factors, the results of which are discussed.