Liver metastasis composed of pure squamous cell carcinoma component from pancreatic pure ductal adenocarcinoma: a case report

BACKGROUND: Liver metastasis of pure squamous cell carcinoma (SCC) from pancreatic ductal adenocarcinoma has not been previously reported. CASE PRESENTATION: A 66-year-old man underwent a computed tomography scan 3 years after surgery for pancreatic head cancer, and the scan revealed a mass lesion in the right lobe of the liver. A liver tumor biopsy was performed, and SCC was diagnosed. Whole sections of the pancreatic head cancer were re-evaluated, but no areas of SCC-like differentiation were identified. Although the pathology differed between the pancreas and liver, metastasis of adenosquamous carcinoma was considered. Three courses of gemcitabine plus nab-paclitaxel were administered to treat the liver metastasis of pancreatic cancer, but no response was attained. Therefore, primary SCC of the liver was considered and hepatic resection was performed. The tumor had invaded the diaphragm, and S5/6 partial hepatic resection with right diaphragm resection was performed. Pathological examination showed pure SCC of the liver, which differed from the pancreatic cancer. KRAS mutations were evaluated in the pancreatic and liver tumor specimens, and Q61R mutation was identified in both specimens. This pure SCC of the liver was diagnosed as metastasis from pancreatic cancer not by histology but by genetic analysis. CONCLUSIONS: This is the first reported case of pure SCC liver metastasis from pancreatic cancer without a squamous cell component in the primary tumor. Evaluation of KRAS mutations in both specimens was useful for diagnosis.