Locally infiltrative inflammatory fibroid polyp of the ileum: report of a case showing transmural proliferation

Abstract

Morphologically, an inflammatory fibroid polyp (IFP) is usually centred in the submucosa. Extension of an IFP to the subserosa with destruction of the muscularis propria is exceedingly rare. Herein, we describe a 70-year-old woman who presented with right lower abdominal pain but was finally diagnosed with an IFP. Contrast-enhanced computed tomography revealed a target-like structure with a hypovascular mass at the leading edge, which was consistent with intussusception due to a tumour. Following surgery, the resected specimen displayed a mass measuring 4 × 3 × 3 cm that was protruding into the lumen. Microscopically, the mass was centred in the submucosa, extending up to the mucosal surface and down to the subserosa and serosa. The muscularis mucosae and muscularis propria were destroyed focally. A PDGFRA gene mutation in exon 2 (1837_1851 del) that was found in this case, as well as a highly infiltrative growth pattern, strongly supported the neoplastic nature of IFP.

Keywords: inflammatory fibroid polyp; serosa; subserosa; transmural proliferation.

Figure 1.

Contrast-enhanced computed tomography. A) Axial; B) Coronal; C) Sagittal images. A target-like structure was revealed with a hypovascular mass (arrows) present at the leading edge. The target-like structure was most evident in (B) (arrowhead).

Figure 2.

Gross examination. A) A mass was observed protruding into the lumen, with surface ulceration of the ileum. The mass was centred in the submucosa and measured 4 × 3 × 3 cm. B) The cut surface of the mass was yellowish-white with a myxoedematous texture. The lesion infiltrated the muscularis propria with probable subserosal extension.

Figure 3.

Histopathological findings. A) Extension into the mucosal surface accompanied destruction of the muscularis mucosae and the surface was ulcerated (×20). B) Extension into the subserosa accompanied focal destruction of the muscularis propria (×20). C) The lesion extended as far as the serosa (×100). D) Cellular composition of the lesion was an admixture of fibroblast-like spindled or polygonal mesenchymal cells (not showing atypia) and inflammatory cells, including many eosinophils with modest infiltration of lymphocytes and plasma cells. The background was myxoedematous with tiny collagen fibers and proliferating small- to mid-sized blood vessels (×400).

Figure 4.

Immunohistochemical findings. A) Lesional cells were positive for CD34 (×400). B) Lesional cells showed focal positivity for alpha smooth muscle actin (×400).