Superficial Angiomyxoma Presenting as an Intra-Luminal Rectal Polyp

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Purpose: INTRODUCTION: Superficial angiomyxomas (SA) are rare, benign, cutaneous tumors that occur mostly on the trunk, head and neck, or lower limb. We report the first case of a superficial angiomyxoma presenting as an ano-rectal polyp. A 51 year old man presented for screening colonoscopy. A full colonoscopy was performed to the cecum. A polypoid mass was noted on retroflexion arising in the region of the anorectal junction (Fig. 1). An MRI revealed only distal rectal wall thickening. The patient underwent transanal excision of a 1.5 × 2 cm pigmented mass located in the anterior quadrant of the rectum at the level of the dentate line. The mass was excised with a 1 cm circumferential margin and the defect was repaired using an endorectal mucosal flap. Histological evaluation was consistent with a superficial angiomyxoma with a lack of nuclear atypia or mitoses (Fig. 2). Immunohistochemical staining was focally positive for CD34 and negative for S 100, SMA, Desmin, and Fli-1. Postoperatively the patient recovered well. Superficial angiomyxoma (SA) have been reported to occur in the scrotum, buttocks and perineum but have never been described to occur intra-luminally in the rectum. Presumably the stratified squamous epithelium of the dentate line provided the tissue source for this SA lesion. SA consist of nodular mucoid tumors interspersed with small to medium sized vessels and a moderate inflammatory cell infiltrate, specifically neutrophils. Immunohistochemical staining of these lesions are variable, limiting their diagnostic usefulness. SA can occur as a part of a complex described by Carny that consists of spotty pigmentation, myxomas, and endocrine dysfunction. Clinically SA present as painless slow growing cutaneous lesions. The lesions are benign with no reported instances of metastatic disease. SA range in size from 0.5 to 14 cms. Age at presentation is between 20 and 40 years old. They have a high local reoccurrence rate of 33%. Our patient had a follow up examination at four months that revealed no gross lesion and biopsies revealed only granulation tissue. In summary we present the first reported case of a superficial angiomyxoma presenting as an intra-luminal rectal polyp. Superficial angiomyxoma should be added to the differential diagnosis of rectal polyps.FigureFigure

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