TONGUE METASTASIS FROM LUNG CARCINOMA IN A CAT WITH ‘FELINE LUNG-DIGIT SYNDROME’.

Feline lung–digit syndrome (FLDS) refers to a clinical entity in which primary lung tumours present because of metastatic lesions in one or more digits. Nevertheless, metastatic manifestations of primary lung tumours in cats may also variously involve eye, muscle, skin, vertebral bone and distal aorta [1]. On the other hand, to the best of our knowledge, tongue metastasis of feline tumours, including lung neoplasms, has not been reported so far, although lingual metastasis has been rarely described in human patients with lung cancer [2-4]. A spayed female, 15 years old domestic shorthaired cat was presented to the Veterinary Teaching Hospital of Teramo for anorexia and lameness. On physical examination, a whitish, 1.5 cm in diameter, nodule was observed on the third digit of the left forelimb, whereas a whitish, slightly raised, 0.5 cm in diameter, nodular lesion was detected on the dorsal surface of the tongue apex. Radiology of thorax and digits, and fine needle aspirate cytology of the digital lesion, allowed to achieve a definitive diagnosis of FLDS. Given the poor health condition and in agreement with the owners, the cat was euthanized. Necropsy exam revealed the presence of a whitish, about 2 cm mass in the middle right lung lobe, with partial involvement of the adjacent cranial part of the caudal right lung lobe. Multiple, whitish, 0.8-1 cm in diameter, sparse nodules were also observed on the spleen. Histological examination of the pulmonary mass revealed a proliferation of highly pleomorphic neoplastic cells, mainly arranged in a solid pattern, with admixed multifocal aspects of acinar or papillary growth, and characterized by multifocal features of squamous differentiation. Tumours cells showed large, pleomorphic nuclei, with multiple large nucleoli, and a high mitotic count (>20 mitosis/10 hpf – 2.37 mm2). Extensive metastatic infiltration was observed in tracheo-bronchial lymph nodes. Nodular lesions of the digit, tongue and spleen were also characterized by a neoplastic proliferation of cells with similar features to those observed in the pulmonary mass. Gross and histopathological findings indicated a diagnosis of pulmonary carcinoma with squamous differentiation, associated with metastasis to the digit, tongue and spleen. Since feline primary lung tumours may be clinically silent in themselves, affected cats are usually presented because of metastases to extra-pulmonary sites. Although lingual metastases are rare, the present findings suggest to remind clinicians that metastatic manifestations of primary lung tumours in cats may variably involve not only digits, but also other multiple extra-pulmonary sites, including tongue.