A CASE OF INFLAMMATORY MYOFIBLOBLASTIC TUMOR OF THE ABDOMINAL WALL

Abstract

A 58-year-old male who presented with the chief complaint of abdominal pain and a palpable mass in the lower abdominal region, was admitted to another hospital, and then was referred to our hospital for a workup and treatment. A hen's egg-sized tumor was palpated in the right lower quadrant of the abdomen, and an inflammatory myofibroblastic tumor (IMT) was thus suspected based on the results of a biopsy. As the result, the tumor was removed under general anesthesia. During surgery the tumor was found in the right lower quadrant of the abdomen which also invaded rectus abdominis muscle. The tumor measured about 50 × 55 × 30 mm in size, and resection was carried out with the surrounding fat tissue and the rectus abdominis muscle. The tumor demonstrated a mixture of yellowish and whitish elements with an unclear margin. A histological examination showed the tumor consisting of spindle-shaped cell bundles, inflammatory cells comprising lymphocytes and plasma cells, and histiocytes. An immunohistochemical examination showed positive staining for HHF-35, α-SMA and negative staining for β-catenin. Based on the above findings, the tumor was diagnosed as IMT. IMT is an inflammatory and neoplastic lesion which consists of myofibloblastic cell bundles and also invasion of inflammatory cells such as lymphocytes and plasma cells. This tumor has recently attracted attention regarding the mechanism of tumor formation.