Inflammatory myofibroblastic tumor in colon

Abstract

Inflammatory myofibroblastic tumor (IMT) is an uncommon mesenchymal solid tumor commonly documented in children and young adults. Here, we report a case of IMT in colon confirmed pathologically after laparoscopic anterior resection. A 35-year-old man presented with anal bleeding after defecation for 2 weeks. Colonoscopy demonstrated a mass with shallow ulceration in the central area and irregular margin accompanied by intact mucosa in the descending colon. Computer tomography showed a well-demarcated and homogenous solitary mass in the descending colon. We performed laparoscopic anterior resection. This case was diagnosed as IMT after microscopic examination. The tumor was composed of a proliferation of spindle-shaped cells arranged in the hyaline material with chronic inflammatory cells, composed mainly of plasma cells and lymphocytes. Immunohistochemically, tumor cells were positive for smooth muscle actin, and vimentin, and negative for desmin, CD117 (c-kit), anaplastic lymphoma kinase-1.

Keywords: Colon; Inflammatory myofibroblastic tumor.

Fig. 1

Endoscopic examination reveals a 4 cm sized irregularly margined mass with intact mucosa (margin) and shallow ulcer (central) in descending colon.

Fig. 2

Trans-axial view (A) and coronal view (B) show a 4.0 cm sized homogeneous enhancing intra-luminal mass (arrow) in descending colon.

Fig. 3

Gross examination reveals a 3.9 × 3.8 cm sized, fungating, white to yellow colored and hard mass in descending colon. Mass involves muscularis propria.

Fig. 4

Tumor is composed of cytologically bland spinle cells arranged in hyaline stroma with scattered inflammatory cells. Inflammatory cells are composed of lymphocytes, histiocytes and plasma cells (A, H&E, ×40; B, H&E, ×400).

Fig. 5

Tumor cells stain strongly for vimentin and variably with myoid markers including smooth muscle actin, muscle-specific actin and desmin (A, vimentin, ×200; B, actin, ×200).