Cetuximab and Dabrafenib Plus Trametinib for Untreated Colonic Metastasis of BRAFV600E Mutant Primary Lung Adenocarcinoma with Signet Ring Cell Features: An Interesting and Rare Case Report

Shujun Jiang,1 Yanran Wu,1 Wenjie Wei,2 Zi Wang,3 Qi Wang1 1Department of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People’s Republic of China; 2Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People’s Republic of China; 3Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People’s Republic of ChinaCorrespondence: Qi Wang, Department of Integrative Traditional Chinese and Western Medicine Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, People’s Republic of China, Tel +86-18627822851, Fax +86-27-83663532, Email wangqixlp@163.comAbstract: Colonic metastases of lung adenocarcinoma are extremely rare. Signet ring cell adenocarcinoma (SRCA) has not been described in patients with gastrointestinal metastasis of lung adenocarcinoma. SRCA is a unique subtype of adenocarcinoma with strong invasion and a poor prognosis, and most SRCA found in the lung are due to gastrointestinal metastases. This report describes a rare case of colonic metastasis from primary lung SRCA. A 64-year-old female was admitted to Sun Yat-sen University Cancer Center for feeling of nausea and malaise. Following a positron emission tomography CT (PET-CT) scan, widespread metastases of tumor cells were found in the bilateral lung, liver, bone, and multiple lymph nodes, but there was no evidence of metastasis to the colon. Two months later, the patient received a liver biopsy at Tongji Hospital in Wuhan. Pathology revealed a poorly differentiated adenocarcinoma with SRCA conformation, but immunohistochemical staining did not identify the original source of tumor cells. Considering that SRCA mainly derives from the gastrointestinal tract and that serum gastrointestinal tumor markers were elevated, we performed gastrointestinal endoscopy on the patient. The results showed an isolated polyp in the colon, and the pathology results indicated a poorly differentiated adenocarcinoma that was considered to originate from the lung based on immunohistochemical staining. Meanwhile, genetic tests identified a BRAF V600E mutation. The final diagnosis was colonic metastasis of BRAFV 600E mutated lung SRCA. Considering the positive expression of EGFR in this case, cetuximab was innovatively added to the first-line treatment regime (dabrafenib and trametinib). To date, the patient has received thirty-two weeks of treatment. Interestingly, lung and liver tumors shrank and tumor markers in the blood normalized. Our findings offer valuable diagnostic and therapeutic information for colonic metastasis of BRAFV600E mutant primary lung adenocarcinoma with signet ring cell features.Keywords: colonic metastasis, lung adenocarcinoma, signet ring cell adenocarcinoma, case report, BRAF V600E mutant