Cutaneous metastases of a bronchial adenocarcinoma in a cat

INTRODUCTION

Cutaneous metastases of internal tumours are rare in cats¹ and have been reported in association with mammary adenocarcinoma and digestive and respiratory tract carcinoma.^2–9 Pulmonary carcinoma with digital metastasis also involving bone has been described by several authors and is the most common cause of tumour metastasis to the skin in cats.^{3–6,8,10–14} Cutaneous metastases may be the first sign of an undiagnosed visceral malignancy, and their recognition may allow rapid diagnosis of this type of cancer.⁶ This case report describes metastasis of a bronchial adenocarcinoma to the abdominal skin in a cat.

CASE REPORT

An 11-year-old, spayed female, Domestic Short Hair cat (4.5 kg) was presented for evaluation of anorexia, abdominal papular dermatitis and intermittent lameness. The cat had been treated 5 weeks prior to referral for coughing and fever with cephalexin 20 mg/kg (Cefalexine, Virbac) orally twice daily and prednisolone 1 mg/kg (Megasolone, Merial) orally once daily for 10 days. Treatment resulted in cessation of coughing. During the 12 months prior to referral, the cat had had several episodes of coughing, and a presumptive diagnosis of asthma was made. The symptoms were successfully treated with intramuscular injections of methylprednisolone 10 mg once monthly for three treatments (Vetacortyl, Vetoquinol).

On physical examination, the cat was depressed and febrile (39.7 °C). Auscultation of the thorax revealed bilateral pulmonary rales, originating mainly from the diaphragmatic lobes. A bilaterally symmetric distribution of erythematous papules and pustules was seen on the abdomen. The lesions were centred on the areolae of the mammary glands. The papules sometimes coalesced to form erythematous plaques (Fig. 1). The lesions were painful. The popliteal lymph nodes were also painful and enlarged. Lameness was not apparent during the physical examination but the cat was reluctant to move, and palpation of both limbs was painful.

Cytological examination of a fine-needle aspirate from an intact pustule revealed inflammatory cells and numerous round to polyhedral cells, which varied in size, had vacuolated foamy cytoplasm and large nuclei with large, irregular-shaped nucleoli. These cells were seen throughout the sample, sometimes in clusters. Some of the cells were multinucleated (Fig. 2). Normal and abnormal mitotic figures were seen and some cells had cilia. These cells were identified as neoplastic epithelial cells. The cilia suggested a respiratory tract origin. Lymph node cytology indicated reactive hyperplasia without evidence of metastasis. The results of a complete blood cell count and biochemistry panel were within the normal ranges and an enzyme-linked immunosorbant assay (ELISA) for feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) antigens was negative. X-Ray examination of the thorax showed diffuse increased density of the lungs in an alveolar pattern with consolidation of the right diaphragmatic lung lobe. Histolopathological examination of biopsy samples of the abdominal skin revealed cords and nodules of neoplastic epithelial cells in the superficial and deep dermis (Fig. 3). There was marked anisocaryosis and moderate mitotic activity. Emboli of these cells were also present in the lymphatics. Based on these findings, a tentative diagnosis of cutaneous metastases of a bronchial carcinoma was made. As the prognosis was poor, the owners elected for euthanasia.

Necropsy findings included generalized pulmonary congestion, numerous small white nodules, with an average diameter of 1–2 mm, disseminated in the pulmonary parenchyma and a larger nodule (1.5 cm) in the right diaphragmatic lung lobe. Similar small nodules were also seen on the parietal pleura. Except for the cutaneous tumours and enlarged popliteal lymph nodes, no other abnormalities were found at necropsy. Samples of pleura, pulmonary parenchyma, and bronchial and popliteal lymph nodes were examined histologically. Most of the bronchi and pulmonary vessels contained proliferative epithelial tissue, which was composed of cells that were cuboidal to columnar with foamy cytoplasm and round vesicular nuclei (Fig. 4). There was moderate mitotic activity and some cells had cilia. Similar lesions were observed in samples of pleura. Reactive hyperplasia was the only change seen in samples of lymph nodes. A diagnosis of cutaneous and pleural metastases of bronchial adenocarcinoma was made.

DISCUSSION

Primary pulmonary neoplasms are rare in cats; most (85%) are adenocarcinomas.¹⁵ In cats, malignant pulmonary tumours frequently metastasize, particularly to the regional lymph nodes, pleura, mediastinum, bones, muscles, heart, brain and spleen.¹⁰ It has been suggested that this distribution is due to direct arterial embolism of tumour cells from the lung.⁵ Long bone and vertebral metastases of bronchial carcinoma have been reported in cats and are more common than metastases to the skin.^11,12 The most common site is the digits where there may be skin as well as bone involvement.^1,4,6,11 There does not appear to be a preferential site for cutaneous metastases of bronchial carcinoma in humans;¹⁶ however, subungueal metastases are frequent.¹⁷

Cutaneous metastases are considered rare in dogs and cats;^1–4 most are carcinomas.¹⁸ In humans, overall incidence (calculated on the basis of the total number of cancer patients observed) of cutaneous metastasis is 5.3%.¹⁹ In cats, information about cutaneous metastases stems from individual case reports^2,3,11 and the majority recorded are digital metastases of bronchial carcinoma.^4,6,15

Feline patients with bronchial carcinomas frequently present with cutaneous lesions as the first symptom encountered.^5,11 However, this cat had respiratory signs weeks to months before the cutaneous lesions. In humans and cats, bronchial carcinoma cutaneous metastases usually consist of one or several nodules.¹⁶ The metastases in this case clinically resembled primary dermatitis, which has been previously described for cutaneous metastases of feline mammary adenocarcinoma² and in human mammary ductal carcinomas (Paget's disease).^20,21

Enlargement of the popliteal and bronchial lymph nodes was not associated with neoplastic emboli. Van der Linde-Sipman & van den Ingh¹¹ suggested that feline pulmonary carcinoma metastasizes haematogenously rather than lymphogenously but dermal lymphatic invasion was seen. Both haematogenous and lymphatic metastatic spread can occur simultaneously.

Pulmonary carcinoma has been reported to metastasize to muscle in cats, and in one report, lameness was the main complaint on presentation.^22,23 The cat in our case had lameness as a major presenting complaint but the post-mortem examination did not reveal metastasis to the muscle. Such metastasis may, however, have been overlooked and the bone marrow was not examined for metastases. It seems unlikely that the pain observed in this case was caused by the lymph node enlargement.

In this case, many criteria suggestive of malignancy²⁴ were present in the aspirated cells: pleomorphism, anisocaryosis, increased mitotic activity, multinucleation and large nucleoli. The round to polyhedral shape of the cells and the organization in clusters was indicative of an epithelial origin. Furthermore, the presence of cilia on some cells suggested a respiratory origin for the primary tumour. The prognosis of bronchial carcinoma with distant metastasis is poor in cats.¹¹ In humans, the treatment of choice is surgical excision because most of the metastases are solitary nodules.¹⁷ Surgical excision was not possible in this case because of the extent of the lesions.

Résumé Cet article décrit un chat présentant des métastases d’adénocarcinome bronchique sur la peau de l’abdomen. Le chat a été traité avec des antibiotiques et des corticoïdes pour plusieurs épisodes de toux, lorsqu’il a présenté un érythème, des pustules et des plaques sur la peau de l’abdomen. L’examen cytologique d’aspriation de pustules cutanées, l’examen radiographique du thorax et l’examen histopathologique de biopsies cutanées ont permis le diagnostic. Le chat a été euthanasié, du fait du mauvais pronostic. L’autopsie a confirmé le diagnostic. Les métastases cutanées des carcinomes pulmonaires sont rares chez le chat, mais sont bien décrites au niveau des doigts, avec une atteinte osseuse. A la connaissance des auteurs, il s’agit du premier cas de métastase de carcinome bronchique à la peau du ventre.

Resumen Este informe describe un gato con metástasis de un adenocarcinoma bronquial a la piel abdominal. El gato había sido tratado con antibióticos y corticoesteroides durante varios episodios de tos, cuando desarrolló un eritema agudo, pústulas y placas en la piel abdominal. El diagnóstico se basó en el examen citológico mediante aspiración con aguja fina de pústulas cutáneas, en el examen radiográfico del tórax y en el examen histológico de muestras de biopsia cutáneas. Teniendo en cuenta el grave pronóstico, el gato fue eutanasiado. Los resultados de la necropsia confirmaron el diagnóstico. Las metástasis cutáneas del carcinoma pulmonar son raras en gatos pero se han descrito en los dígitos con la implicación subyacente del hueso. Según nuestros conocimientos, éste es el primer informe de metástasis de un carcinoma bronquial felino a la piel ventral.

Zusammenfassung Dieser Bericht beschreibt eine Katze mit Metastasen eines bronchialen Adenocarcinoms in der abdominalen Haut. Die Katze wurde wegen mehrerer Episoden von Husten mit Antibiotika und Kortikosteroiden behandelt, als sie akut Erythem, Pusteln und Plaques auf der abdominalen Haut entwickelte. Die Diagnose basierte auf zytologischer Untersuchung von Feinnadelaspiraten kutaner Pusteln, Röntgenuntersuchung des Thorax und histologischer Untersuchung von Hautbiopsien. Da die Prognose schlecht war, wurde die Katze euthanasiert. Eine Autopsie bestätigte die Diagnose. Kutane Metastasen von Lungenkarzinomen bei der Katze sind selten, wurden aber in den Zehen mit zugrundeliegender Knochenbeteiligung beschrieben. Nach Wissen der Autoren ist dies der erste Bericht über Metastasen eines felinen Brocnchialkarzinoms in ventraler Haut.