Inflammatory fibroid polyp of rectum mimicking rectal cancer

Abstract

Inflammatory fibroid polyps (IFPs) are rare benign tumors of the rectum. Mutation and activating platelet-derived growth factor receptor alpha (PDGFRA) contribute to tumor development. We present a case of IFPs in the middle rectum that mimic rectal cancer. A 65-year-old woman presented with the symptom of fresh blood in the stool and body weight loss of 6 kg in the preceding 3 weeks. A rectal polypoid tumor was noted upon digital examination. Sigmoidoscopy showed a middle rectal tumor measuring 3 × 2.7 cm with obstruction. Computed tomography (CT) scans of the abdomen showed a rectal tumor that had invaded the sacral bone and was associated with four enlarged lymph nodes greater than 1 cm. The radiological report suggested a diagnosis of rectal cancer with lymph node metastases. To remove the obstruction, the patient was initially treated with excision of the tumor and loop sigmoidal colostomy to the abdomen wall. Total mesorectal resection of rectal and sacral tumor followed 10 days later. Histopathological examination of the rectal and sacral tumor showed proliferation of vessels, fibroblast-like spindle cells, and mixed inflammatory cells, including the plasma cells and eosinophils. The spindle cells were diffusely positive to PDGFRA and were focal positive to CD34 and smooth muscle actin. Based on histopathological and immunohistochemical findings, the diagnosis of IFP is indicated. This was the first reported case of IFPs of the rectum presenting with lymph node enlargement and attachment to the sacrum mimicking rectal cancer.

Keywords: Inflammatory fibroid polyp; PDGFRA; Rectum; Sacrum.

Figure 1

(A) Sigmoidoscopy revealing a polypoid lesion (3 × 2.7 cm) in the middle rectum with lumen obstruction. (B) Abdominal computed tomography scan of the patient revealing a tumor (3 × 2.7 cm, arrow) of rectum attached to the sacral bone.

Figure 2

(A) Cross‐sections of rectal tumor of the patient showing a polyp‐like lesion following the excision of tumor and loop sigmoidal colostomy. (B) Photomicrogram demonstrating the presence of proliferative spindle cells, vessel proliferation, and mixed inflammatory cells in the tumor (hematoxylin and eosin (H&E) staining, original magnification ×400).

Figure 3

Immunohistochemical staining of platelet‐derived growth factor receptor alpha (PDGFRA) and CD34 of the rectal tumor. (A) The proliferative spindle cells are diffusely positive to PDGFRA (original magnification ×400). (B) The proliferative vessels and few stromal cells are positive stains to CD34 (original magnification ×400).