Triple gastrointestinal malignancies with tumor-to-tumor metastasis from gastric adenocarcinoma to small bowel adenocarcinoma: A case report

Abstract

BACKGROUND

Gastric cancer is the sixth most common malignancy worldwide. Metastatic small intestinal malignancy is more common than primary small intestinal malignancy; however, metastasis from gastric cancer to the small intestine is extremely rare. Triple primary gastrointestinal malignancies have been sporadically reported and linked to rare genetic mutations. Rarely, tumor-to-tumor metastasis (TTM) occurs when a primary donor tumor metastasizes to another distinctive recipient primary tumor. Herein, we present the first reported case of TTM of a donor gastric adenocarcinoma to a recipient small intestinal adenocarcinoma in a patient with a previous history of colon cancer, along with an extensive literature review of all reported cases of TTM originating from gastric adenocarcinoma.

CASE SUMMARY

A 57-year-old male with a history of colon cancer remained disease-free for eight years before presenting with abdominal pain, easy fatigability, and diarrhea. Upper endoscopy showed a fungating gastric mass, which was diagnosed as moderately differentiated primary gastric adenocarcinoma. After four cycles of neoadjuvant chemotherapy, exploratory laparotomy revealed an ileal mass, histopathologically diagnosed as moderately differentiated primary small intestinal adenocarcinoma with metastatic mucinous adenocarcinoma of gastric origin, consistent with TTM. The patient received 20 cycles of chemotherapy but unfortunately passed away secondary to septic shock.

CONCLUSION

TTM of gastric adenocarcinoma to small intestinal adenocarcinoma is a rare and challenging clinical entity that requires a high index of suspicion and meticulous histopathological and immunohistochemical evaluation. Its pathophysiology is not fully understood, and both prognosis and treatment intent depend on the type of donor tumor and the nature of the recipient tumor, whether benign or malignant.

Keywords: Collision tumor; Gastric adenocarcinoma; Seed and soil; Small bowel adenocarcinoma; Tumor to tumor metastasis; Case report

Core Tip: Metastatic involvement of the small intestine usually results from direct invasion by adjacent organs, while hematogenous spread is rare. Interestingly, metastatic tumors are more common than primary small bowel malignancies due to protective mucosal and immunological factors. Tumor-to-tumor metastasis is an exceptionally rare event, defined as the growth of a metastatic tumor within another primary neoplasm. Among reported cases, renal cell carcinoma is the most frequent recipient, and gastric primaries are exceedingly uncommon. This report presents the first documented case of Recurrent gastric adenocarcinoma metastasizing into a primary small bowel adenocarcinoma, highlighting the importance of thorough histopathological evaluation.