18F-FDG PET/CT and 68Ga-Pentixafor PET/CT Findings of Gastric Mucosa-associated Lymphoid Tissue Lymphoma Transformation to Diffuse Large B-cell Lymphoma

A 66-year-old man with a pathology-confirmed gastric mucosa-associated lymphoid tissue (MALT) lymphoma underwent imaging with both 68 Ga-pentixafor and 18 F-FDG PET/CT. The 18 F-FDG PET/CT demonstrated intense FDG uptake in the gastric lesion, whereas the 68 Ga-pentixafor PET/CT showed only minimal tracer uptake. Subsequent histopathologic evaluation confirmed a transformation into aggressive diffuse large B-cell lymphoma (DLBCL). This case underscores the importance of recognizing atypical imaging patterns to identify histologic transformation and guide timely clinical intervention.