Colonic inflammatory myofibroblastic tumor immunonegative to ALK protein presenting with intestinal obstruction

A 55-year-old male presented with a 2-month history of intermittent post-prandial lower abdominal pain, constipation, and bleeding per rectum. Laboratory tests revealed hemoglobin of 8.5 mg/dL. Colonoscopy demonstrated a stricturing lesion in the proximal transverse colon. Biopsies demonstrated mucosal exudate, ulceration, and inflammation. PET-CT scan showed asymmetric circumferential wall thickening involving a distal segment of the transverse colon, suspicious for malignancy. The patient underwent a right extended hemicolectomy. Histopathology revealed a tumour composed of fascicles of uniform to plump spindled cells in a background of inflammatory infiltrate composed of plasma cells and eosinophils. Immunohistochemistry demonstrated distinct SMA positivity and variable Desmin reactivity, while ALK, ROS1, and Pan-TRK were negative. A diagnosis of inflammatory myofibroblastic tumor (IMT) was established. At initial six-month follow-up, the patient was asymptomatic and had gained weight. IMT of the colon, is a rare tumour, mimicking the more common adenocarcinoma of the colon, in terms of its clinical presentation and imaging. It is yet another differential in a patient presenting with weight loss, anaemia and bleeding per rectum when investigations show a mass lesion in the colon. Surgery remains the primary treatment modality.