Pulmonary arteriovenous fistula arising in a renal cell carcinoma lung metastasis

Abstract

Introduction

Pulmonary arteriovenous fistula (PAVF) or malformation is an abnormal vascular connection between a pulmonary artery and a pulmonary vein. Most often congenital in nature, it may also be found in a variety of acquired conditions. Acquired PAVFs have been reported after chest surgery, correction of congenital heart disorders by Glenn (superior venal cava-right pulmonary artery anastomosis) or Fontan procedures, or penetrating chest trauma, and in actinomycosis, schistosomiasis, cirrhosis, metastatic thyroid carcinoma, metastatic choriocarcinoma, and mitral stenosis.1, 2 and 3 To our knowledge no case of acquired PAVF has been reported as occurring at the site of a pulmonary metastasis from renal cell carcinoma. Renal cell carcinoma, the most common cancer of the kidney, is characterized by varied and obscure clinical and radiological features, which include unusual metastatic sites and paraneoplastic, paraendocrine, serological, and vascular syndromes.4 Here, we report the first known case of PAVF arising from a renal cell carcinoma pulmonary metastasis.

Case report

A 73-year-old woman with metastatic renal cell carcinoma to the lungs presented with progressive dyspnoea of 3-months duration. Thirteen years before this complaint, the patient had undergone a left nephrectomy due to a renal mass and secondary absolute polycythaemia as a paraneoplastic syndrome, which had resolved after the nephrectomy. The pathology report had shown an 8-cm sized tumour of nuclear grade I without vascular invasion. At that time, extensive metastatic lesions were found in both lungs and were confirmed by open lung biopsy of the left lower lobe but no metastatic disease was found in an interlobar lymph node that was removed uneventfully. Despite chemotherapy with tumour necrosis factor and interferon alpha (IFN-α), bilateral lung metastases progressed. Therefore, the chemotherapy regimen was changed to 5-fluorouracil plus low-dose IFN-α and then floxuridine plus IFN-α. With floxuridine and IFN-α, the lung lesions had markedly regressed for the initial 4 years, and thus, all anticancer drugs were discontinued for almost 3 years. This was followed by progression of the lung metastases and chemotherapeutic agents were re-administered and discontinued after regression or stabilization, repetitively.

Three months before her current presentation, because the metastatic lung lesions showed slight progression on chest computed tomography (CT), therapy with floxuridine plus IFN-α was resumed; however, the patient denied dyspnoea at that time. She then began complaining of shortness of breath with dyspnoea at rest and minimal exertion, which worsened over the ensuing 2–3 months. She denied any productive cough or pleuritic chest pain, but reported occasional haemoptysis. The patient's daughter reported that her mother's fingernails turned blue when she exerted herself. As the metastatic lung lesions progressed, her polycythaemia recurred, and she underwent repeated phlebotomies.

Results of the physical examination were unremarkable. An arterial blood gas analysis performed on supplemental oxygen via nasal cannula (FiO2 60%) showed a pH of 7.4 (reference range, 7.35–7.45), pCO2 of 31 mmHg (reference range, 35–45 mmHg), pO2 of 62 mmHg (reference range, 75–100 mmHg), HCO3 of 18 mmol/L (reference range, 22–26 mmol/L), and a base excess of −7 mmol/L (reference range, −2–3 mmol/L). The erythropoietin level was 83.4 mU/ml (reference range, 4.1–19.5 mU/ml). Chest radiograph (Fig. 1) and CT of the chest were obtained and compared with prior images. The results showed stable metastatic disease in the lungs with no change of mediastinal and hilar adenopathy. Because of the hypoxia, a CT angiogram was ordered to exclude pulmonary emboli. On CT angiogram, there were no pulmonary emboli demonstrated. There were multiple avidly enhancing pulmonary nodules and masses demonstrated, ranging in size from 1–5 cm, consistent with this patient's known pulmonary metastases. Two of the 5-cm masses were centrally located in the perihilar region (Fig. 2).