MDCT features of succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumours

Objective: To describe the multidetector CT (MDCT) features and metastatic pattern of succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumours (GISTs). Methods: In this institutional review board-approved, Health Insurance Portability and Accountability Act-compliant study, we retrospectively identified 34 patients (20 females; mean age, 34 years; range, 12-59 years) with histopathology-confirmed SDH-deficient GIST, who were seen at our institution from 1999 through 2012. MDCT of primary tumour in 8 patients and follow-up imaging in all 34 patients over median follow-up of 106 months [interquartile range (IQR), 52-175 months] were reviewed by two radiologists in consensus. Clinical information was extracted from electronic medical records. Results: Primary tumour in all 34 patients was located in the stomach. Mean tumour size (n=58) was 9.6 cm (range, 8-14 cm). Primary tumours were lobulated, variable in growth pattern, hypo-(1/ 8) to isodense (7/ 8) and similar in enhancement to the skeletal muscle. Two were multifocal, four of eight had necrosis and one of eight had haemorrhage. Tumour rupture with haemoperitoneum and tumour-bowel fistula was noted in one patient each. During follow-up, 12/ 34 patients developed tumour in surgical bed, and 28/ 34 patients developed metastases. Most common sites of metastases were the liver (24/ 34), peritoneum (20/ 34) and lymph nodes (18/ 34). Carney triad and Carney-Stratakis syndrome were noted in 5/ 34 and 1/ 34 patients, respectively. At the time of writing, six patients had deceased at a median interval of 109 months (IQR, 54-126 months). Conclusion: SDH-deficient GISTs occur in young patients, commonly arise in stomach, can be multifocal and may be associated with Carney triad or Carney-Stratakis syndrome. They frequently metastasize to lymph nodes in addition to the liver and peritoneum and are associated with indolent course despite metastatic spread. Advances in knowledge: The presence of features unusual for conventional GIST on imaging should alert the radiologist for the possibility of SDH-deficient GIST, especially, because SDH-deficient GISTs are resistant to imatinib. Young age at diagnosis, prolonged survival, association with Carney triad and Carney-Stratakis syndrome and occurrence of concurrent renal cell carcinoma and thyroid malignancies necessitates long-term follow-up of patients with SDH-deficient GISTs.