Abdominal cyst of unclear aetiology: gastrointestinal stromal tumour or reactivation of abdominal tuberculosis

Differential diagnosis of a new abdominal mass is broad and includes infection, malignancy and other inflammatory processes. Definitive diagnosis may be challenging without invasive biopsy, as history, physical exam and imaging may be non-specific. A 69-year-old man with a history of abdominal tuberculosis presented with a new painful abdominal cyst consistent with reactivation of tuberculosis versus new malignancy. Investigations revealed 4+ acid-fast bacilli from the aspirate suggestive of tuberculosis, but no improvement was noted on antituberculous therapy. Core needle biopsy noted c-KIT-positive spindle cells, diagnostic for a gastrointestinal stromal tumour, while cultures grew non-tuberculous mycobacteria.

Outstanding Response to Sorafenib in a Patient with Metastatic Gastrointestinal Stromal Tumour

Gastrointestinal stromal tumour (GIST) is the most common sarcoma and can be seen in any part of the gastrointestinal tract. The effect of tyrosine kinase inhibitors varies with mutation status in receptor tyrosine kinase KIT and in platelet-derived growth factor receptor A (<i>PDGFRA</i>). This case presents a 61-year-old man, diagnosed with an 11-cm GIST located at the stomach with a high risk of recurrence. The patient showed intolerance to imatinib shortly after introduction and subsequently progressed on sunitinib and nilotinib. The patient started fourth-line treatment with sorafenib with an impressive response to a point at which metastases intra-abdominally and in the liver could be resected. After surgery, sorafenib was restarted. Due to toxicity, sorafenib dose was reduced over time. The dose was insufficient to control the disease since a new recurrence was detected. Mutation analyses revealed a GIST harbouring a deletion of codon p.I843_D846del, located at <i>PDGFRA</i> exon 18, right next to the codon D842 where mutations are known leading to imatinib resistance. In this case, the GIST was highly sensitive to sorafenib, and the response was dose related. It is mandatory to perform mutation analyses on primary tumour and at recurrence in the decision-making of the correct treatment for the patient. In March 2021, the patient had been in treatment with sorafenib for 12.5 years and was still without signs of recurrence. A multidisciplinary approach was essential for the long-term survival of the patient in this case.