GIST-ery solved: story of an intestinal mass in a young lady.

A 19-year-old woman presented with abdominal pain and a palpable mass, initially suspected to be a gastrointestinal stromal tumor (GIST) based on imaging. Surgical excision revealed a sclerotic spindle cell neoplasm with minimal cytological atypia, but immunohistochemistry (IHC) was negative for GIST-specific markers. The pan-negative IHC profile, along with calcification foci and low Ki67 index (<1%), led to a diagnosis of calcifying fibrous tumor (CFT). This case highlights the importance of precise diagnostic evaluation and consideration of rare entities like CFT. Comprehensive histopathological evaluation and IHC are essential diagnostic tools, as they can distinguish between GIST and CFT, leading to accurate treatment and patient management. This case underscores the value of thorough pathological assessment in resolving diagnostic challenges.