Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 8 3 2023 12 03 130 134 Nitin Gupta Department of Radiation Oncology and Nuclear Medicine, Dr Rajendra Prasad Government Medical College, Kangra at Tanda Himachal Pradesh, India Shalini Verma Department of Radiation Oncology and Nuclear Medicine, Dr Rajendra Prasad Government Medical College, Kangra at Tanda Himachal Pradesh, India Priyanka Thakur Department of Radiation Oncology, AIIMS, Bilaspur, Himachal Pradesh India. 2023 08 01 2023 08 15 Gastrointestinal stromal tumors (GIST) are rare tumors accounting for less than 1% of primary neoplasia of the digestive tract. They can also occur outside the GIT, where they are called extra gastrointestinal stromal tumors (EGIST), which are extremely rare tumors. GISTS and EGISTS have similar histo-pathological and molecular profiles. Though these are known to be FDG avid, some of the atypical GISTS can be FDG negative or only minimally FDG avid.Here, an unusual case of a 57-year-old female with FDG avid solitary chest wall mass is presented, which after biopsy and immune-histochemistry was proven as EGIST. She underwent en block resection of the tumor and is presently on adjuvant treatment with Imatinib mesylate. This case report highlights the importance of considering EGIST as a differential diagnosis of a solitary chest wall mass and the utility of 18F- FDG PET/CT in its management. https://crcp.tums.ac.ir/index.php/crcp/article/view/852