Case 1: Malignant T-cell Lymphoma of the Gallbladder: A 54-year-old male presented with acute abdominal pain and pleural effusion, clinically diagnosed with acute cholecystitis. Pathological examination of the gallbladder revealed mucosal ulceration with diffuse infiltration by atypical lymphoid cells. Immunohistochemistry showed positive staining for TdT, BCL-2, and CD3. The diagnosis was malignant T-cell lymphoma-NOS (Not Otherwise Specified).

Case 2: Histiocytic Sarcoma of the Ileum: A 26-year-old male with a history of chronic diarrhea, initially diagnosed with inflammatory bowel disease (IBD), developed an obstructive ileal mass. Histological analysis of the ileum showed infiltration by atypical lymphoid cells with nuclear pleomorphism and multinucleated cells. Immunohistochemistry was strongly positive for CD68. The diagnosis was histiocytic sarcoma of the ileum.

Discussion: The gastrointestinal tract, particularly the small intestine, is a common site for extra nodal lymphomas, though rare forms such as gallbladder T-cell lymphoma and ileal histiocytic sarcoma present significant diagnostic challenges. Accurate diagnosis relies on comprehensive histopathological and immunohistochemical analysis. Treatment typically involves a combination of surgical resection, chemotherapy, and radiation, with histiocytic sarcoma often associated with a poor prognosis due to its aggressive nature.

Conclusion: These cases highlight the importance of thorough diagnostic evaluation in rare gastrointestinal lymphomas. The complexity of these conditions necessitates careful histological and immunohistochemical assessment to guide effective treatment strategies and improve patient outcomes.