An Unusual Case of Isolated Peritoneal Metastases from Lung Adenocarcinoma

INTRODUCTION: Peritoneal metastases from lung cancer are a rare event. In this paper, we report the case of a patient with adenocarcinoma of the lungs who had isolated peritoneal metastases at the time of diagnosis. CASE REPORT: We report a 55-year-old female who presented with shortness of breath, decreased effort tolerance, cough, and weight loss. Her initial chest X-ray and subsequent chest CT showed a 12 × 9 × 8 cm mass in the middle lobe of the right lung. The histopathological examination of her biopsy material was consistent with a thyroid transcription factor-1 positive lung adenocarcinoma. In the abdomen, a 5.3-cm mass was identified. A biopsy and immunohistochemistry revealed a lung adenocarcinoma. The patient was administered chemotherapy based on carboplatin-paclitaxel-bevacizumab, but only with a partial response. Six months later, the patient showed brain metastases. Therefore, a second-line treatment based on pemetrexed was administered for 9 courses, and a clinical and radiological response was observed. The chemotherapy was stopped and the patient did not exhibit any symptoms of progression while waiting for a new evaluation. DISCUSSION: The incidence of peritoneal involvement of lung cancer without metastases in other parts of the body is scarcely encountered in clinical practice. Out of the different types of lung cancers, adenocarcinoma and large cell carcinoma are most likely to metastasize in the peritoneum. Immunohistochemical staining patterns were important in the differential diagnosis with the other etiologies for peritoneal metastasis and the mesothelioma. Peritoneal metastases are indicative of a disseminated disease and prognosis is extremely poor.