Rectal metastasis in Lung cancer: A case report and review of the literature

Abstract

Gastrointestinal metastasis in lung cancer is not commonly encountered clinically, of which rectal involvement is a sporadic event. There were few reports about rectal metastasis in lung cancer. All of them had a dismal prognosis. We report a case of synchronous rectal metastasis in a lung cancer patient with a different clinical scenario, treatment, and prognosis. The patient presented with infrequent hematochezia due to a rectal mass confirmed as adenocarcinoma on core biopsy. Computer tomography showed many nodules in both lungs, which raised the initial diagnosis of pulmonary metastasis in rectal cancer. However, we decided to perform immunohistochemistry on the rectal biopsy specimen, which, surprisingly, revealed the site of origin was from the lung. Subsequently, next gene sequencing was performed and detected an exon 19 deletion on the EGFR gene. Though he had infrequent hematochezia, we decided to treat him with Erlotinib (a first-generation TKI) and closely monitored the rectal symptoms. Six months later, he achieved a complete response of both lung and rectal lesions. At present, he has been progression-free for 14 months. Thus, physicians should always be aware of this differential diagnosis in synchronous tumors and carefully consider the optimal treatment to start.