Primary colorectal inflammatory myofibroblastic tumour: a clinicopathological and immunohistochemical study of seven cases

Aims Primary colorectal inflammatory myofibroblastic tumours are rare. Here we report seven such cases to demonstrate their clinicopathological features and prognosis. Methods Clinical and pathological data of seven cases of colorectal inflammatory myofibroblastic tumour were reviewed. Immunohistochemical staining was also performed. Results The presenting symptoms included abdominal or pelvic mass (7 patients), abdominal pain (7 patients), and lower gastrointestinal haemorrhage (2 patients). The tumour size ranged from 3.8 cm to 6.3 cm in greatest dimension. Histologically these tumours showed three patterns: myxoid hypocellular, fascicular, and hyalinised pattern. A lymphoplasmacytic infiltrate was present in all seven tumours. Mitotic figures were 0~2 per 10 high power fields (HPF) in five cases and were focally up to 4~6 per 10 HPF in two tumours. Nuclear atypia was mild in five and moderate focally in two tumours. Necrosis was absent. Anaplastic lymphoma kinase (ALK), smooth muscle actin, and vimentin staining were present in all tumours. S100, CD21, CD34, CD35, desmin, CK, CD68, and CD117 were negative in all inflammatory myofibroblastic tumours. The patients were followed up for 3–8 years (mean 4.9 years). Five patients were alive without evidence of disease after tumour resection. Two patients had a tumour recurrence 14 and 18 months after the initial surgery, respectively. A second surgical resection was performed for the recurrent tumours and the patients have been free of disease since (now 22 and 35 months after the second surgery, respectively). Conclusions Colorectal inflammatory myofibroblastic tumours are rare, benign or low malignant tumours and ALK positivity is helpful in pathological diagnosis.