Rare cause of fever of unknown origin: gastrointestinal stromal tumour.

A 44-year-old man presented with fever (low to high grade) for 2-month duration despite treatment with oral antibiotics and antipyretics. Further, enquiry did not yield any potentially explanatory clues to a diagnosis. Physical examination revealed only left axillary lymphadenopathy, but was otherwise unremarkable. A number of diagnosis included tuberculosis, malignancy, lymphoma, connective disease disorder and infective endocarditis. Further evaluation revealed severe anaemia due to iron deficiency which was supported with blood transfusion and oral iron supplementation. Septic work-up including blood cultures and urine culture sterile and procalcitonin, but all these proved negative. Transthoracic echocardiography followed by transoesophageal echocardiography did not reveal any vegetations suggestive of infective endocarditis. Contrast-enhanced CT of chest and abdomen showed a polypoidal mass in the caecum. Lymph node biopsy from left axillary lymph node showed changes consistent with reactive hyperplasia. A bone marrow biopsy was inconclusive. Mantoux test was negative. A colonoscopy revealed a polypoidal growth arising from caecum with dull-looking mucosa. Biopsy of the mass suggested a leiomyoma. Positron emission tomography CT showed fluorodeoxyglucose (FDG)-avid caecal mass with FDG-avid mesenteric lymph nodes (figure 1). Inspite of extensive work-up, we could not find a source of the fever except for caecal mass. Thus, in the absence of other explanatory findings, a decision for resection of the mass was taken. A laparoscopic right hemicolectomy done with primary anastomosis. Histology confirmed a gastrointestinal stromal tumour (figure 2, which was smooth muscle actin positive (figure 3), S-100 positive, vimentin positive, but c-KIT negative (figure 4), CD34 positive and desmin negative. Additional immunohistochemistry and gene mutational analysis could not be done due to resource limitations. The postoperative course was good, and the patient was followed for 9 months after surgery with good clinical recovery and no further fever. This case illustrates the need for high index of suspicion to diagnose malignancy as cause of fever.