Rapid onset lung squamous cell carcinoma with prominent peritoneal carcinomatosis and an eosinophilic leukemoid reaction, with coexistence of the BRAF V600E and oncogenic KRAS G12A mutations: A case report.

Peritoneal carcinomatosis from lung cancer is rare, particularly from lung squamous cell carcinoma (LSCC). Concurrent somatic BRAF and KRAS mutations within the same tumor specimen have not been reported. The present study describes the case of a treatment-naïve LSCC patient with coexisting BRAF V600E and oncogenic KRAS G12A mutations in the primary lung lesion and the peritoneal metastases. The patient presented with prominent peritoneal carcinomatosis and an eosinophilic leukemoid reaction, but no respiratory symptoms. The patient succumbed 8 days after the onset of the condition due to rapid aggravation of the peritoneal carcinomatosis. To the best of our knowledge, this is the first study concerning the coexistence of BRAF and KRAS mutations in LSCC. Intensive activation of ERK was also observed in the primary lung lesion and the peritoneal metastases. Although the exact pathogenesis was unclear, the observations indicated that in the present study, the BRAF V600E and KRAS G12A mutations may have cooperate in inducing the malignant phenotype of LSCC. This case also highlighted the potential aggressive course and unusual pattern of spread of this specific dual-mutated tumor.