Response Assessment of Recurrent Extragastrointestinal Stromal Tumor of the Urinary Bladder to Imatinib: Findings on Serial 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography Scans.

Extragastrointestinal stromal tumors (EGISTs) are rare mesenchymal tumors occurring outside the gastrointestinal tracts that have similar histological and immunohistochemical characteristics similar to those of gastrointestinal stromal tumors. EGISTs involving the urinary bladder are extremely rare tumors with very few reports mentioned in the literature. We present a case of a 48-year-old man, known case of biopsy-proven EGIST of the urinary bladder that presented with recurrence after partial cystectomy and 18F-fluorodeoxyglucose positron emission tomography-computed tomography scans documenting the response assessment of the recurrent tumor to imatinib. Copyright:

A 48-year-old man underwent partial cystectomy with loop ileostomy surgery for urinary bladder mass. Surgical pathology from the mass was suggestive of extragastrointestinal stromal tumor (EGIST) of the urinary bladder. The patient came to the surgery outpatient department after 1 year with chief complaints of intermittent abdominal pain. Cystoscopy and biopsy were done, which were suggestive of recurrent disease in the urinary bladder. 18F-fluorodeoxyglucose positron emission tomography–computed tomography (FDG PET-CT) was advised by the referring surgeon for accurate delineation of the extent of recurrent disease. PET-CT scan revealed focal wall thickenings along the superolateral wall of the urinary bladder showing increased FDG uptake [Figure 1a-e]. Suspecting recurrence of the primary tumor, the patient was started on 400 mg bd imatinib, and a follow-up PET-CT scan was done after 1 year. PET-CT scan findings revealed no significant residual disease in the urinary bladder or elsewhere in the body [Figure 2a-e], suggesting complete response to imatinib therapy. EGISTs are mesenchymal tumors occurring outside the gastrointestinal tract, with morphological, immunophenotypic, and molecular biological characteristics very similar to those of gastrointestinal stromal tumors.[1] EGISTs are a rare clinical entity, accounting for <5% of the soft-tissue tumors.[234] There have been very few reports in the literature regarding EGIST of the urinary bladder.[56789] The authors through this case want to describe this very rare tumor which has limited description in the literature and underscore the importance of 18F-FDG PET-CT over conventional imaging modalities such as CT in the evaluation of response assessment to the chemotherapeutic agents.

Figure 1

(a) Maximum intensity projection image of fluorodeoxyglucose positron emission tomography–computed tomography scan showing focal area of radiotracer uptake in the pelvic region (black arrow). (b) Axial computed tomography section of the pelvis showing abnormal focal wall thickening in the superolateral aspect of the urinary bladder showing increased fluorodeoxyglucose uptake in the fused positron emission tomography–computed tomography image (c, white arrow). (d) Sagittal section of the abdomen showing abnormal focal wall thickening in the superolateral aspect of the urinary bladder showing increased fluorodeoxyglucose uptake in the fused positron emission tomography–computed tomography image (e, white arrow)

Figure 2

(a) Maximum intensity projection image of the follow-up fluorodeoxyglucose positron emission tomography–computed tomography scan showing no abnormal focal radiotracer uptake in the pelvic region with physiologic radiotracer uptake in the urinary bladder. (b) Axial computed tomography section of the abdomen showing no abnormal wall thickening or abnormal fluorodeoxyglucose uptake in the fused positron emission tomography–computed tomography image (c). (d) Sagittal computed tomography section of the abdomen showing no abnormal wall thickening or abnormal fluorodeoxyglucose uptake in the fused positron emission tomography–computed tomography image (e)

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