Less than 1% of malignant tumors of the hepatobiliary system are intrahepatic sarcomatoid cholangiocarcinomas, a rare malignant tumor of the liver. Based only on clinical presentation and imaging, this entity is readily mistaken for hepatocellular carcinoma. In this article, we describe the case of a 36-year-old male patient who had a history of "cirrhosis B" and was hospitalized for six months due to increased alpha-fetoprotein. Magnetic resonance imaging (MRI) and computed tomography (CT) revealed a 63x 90 mm mass in segments V and VI of the liver, with thrombosis in the right branch of the portal vein. Following the patient's laparoscopic lobectomy and cholecystectomy, sarcomatoid cholangiocarcinoma of the right side of the liver was discovered by histopathological and immunohistochemical examinations. This case report seeks to increase understanding of intrahepatic sarcomatoid cholangiocarcinoma and its diagnosis while reducing the occurrence of clinical misinterpretation.

It is highly uncommon for the gastrointestinal tract to be affected by follicular dendritic cell sarcoma(FDCS), a rare mesenchymal tumor that typically develops in the lymph nodes. Here, we describe a 64-year-old woman who discovered a lump in her left upper abdomen six months ago and was just taken to the hospital due to excruciating abdominal pain. An abdominal CT scan shows a soft tissue mass around the cardia. The patient underwent “radical total gastrectomy and esophagojejunostomy (Roux-Y anastomosis)”. Immunohistochemical and postoperative histopathology results were compatible with FDCS. The pathogenic characteristics of FDCS have received substantial discussion in the literature, however, the imaging characteristics of FDCS that involves the stomach and abdominal cavities have received less attention. This case report aims to enhance clinicians' understanding and diagnosis of dendritic cell sarcoma in the stomach and abdominal cavities of abdominal follicles and reduce the rate of clinical misdiagnosis.

Rationale: Follicular dendritic cell sarcoma (FDCS) is a rare mesenchymal tumor that typically develops in lymph nodes; it is clinically uncommon and has only occasionally been documented in cases of soft tissue, liver and spleen, and retroperitoneum; it is also extremely uncommon to develop in the stomach. Patient concerns: A 64-year-old woman who discovered a lump in her left upper abdomen 6 months prior and was taken to the hospital due to excruciating abdominal pain. Diagnosis: An abdominal computed tomography scan showed a soft tissue mass around the cardia. The immunohistochemical and postoperative histopathology results were compatible with FDCS. Interventions: The patient underwent “radical total gastrectomy and esophagojejunostomy” (Roux-Y anastomosis). Outcomes: The patient recovered well 2 months after surgery. Lessons: We report a case of FDCS occurring in the stomach and abdominal cavity, which was unique in terms of clinical location, clinical presentation, and imaging signs. This case report aims to enhance clinicians’ understanding and diagnosis of FDCS in the stomach and abdominal cavity and reduce the rate of clinical misdiagnosis.