Incidental finding of bone tracer accumulation in gastrointestinal stromal tumor: Two case reports.

Bone scintigraphy with technetium-labelled diphosphonates is widely used for evaluating skeletal pathology. However, extra-osseous uptake may also be encountered and can indicate underlying neoplastic processes. We report 2 cases of incidental intra-abdominal uptake on bone scans, later confirmed as gastrointestinal stromal tumors. In both cases, planar bone scintigraphy revealed focal tracer uptake in the abdomen, which SPECT/CT localized to exophytic gastric masses with intralesional calcification. Histopathological confirmation was obtained via endoscopic biopsy and surgical resection. These cases highlight the diagnostic value of hybrid SPECT/CT imaging in evaluating unexpected soft tissue uptake, enabling accurate anatomical localization and differentiation from physiological or benign causes. Although the mechanisms of diphosphonate accumulation in extra-osseous neoplasms are not fully understood, contributing factors may include calcification, vascularity, and altered tissue microenvironment. Recognition of such findings can facilitate timely diagnosis and management. Awareness of neoplastic causes of extra-osseous uptake is essential for interpreting physicians to guide appropriate clinical follow-up.