EP740 - Cellular Angiofibroma Arising in a Giant Anal Skin Tag: A Rare Case Report

Purpose/Background: Cellular angiofibroma (CAF) is a rare mesenchymal neoplasm first described in 1997, characterized by spindle cells and prominent vasculature. It is a benign tumor with a predilection for the genital tract, most commonly occurring in the inguinoscrotal or vulvovaginal regions. CAF with anorectal involvement accounts for only 2% of all cases of CAF cases documented in the literature. Diagnostic workup focuses on differentiating these tumors from more aggressive ones through histopathology and immunohistochemistry. The current standard for treatment is surgical resection with clear margins as there is a low risk of local recurrence. In this report, we present an unusual presentation of cellular angiofibroma in a giant anal skin tag.

Methods/Interventions: 23-year-old patient who was seen in the outpatient setting for rectal bleeding, peri-anal pain, and swelling for one month associated with occasional constipation. Inspection of the perineum showed a large 10 cm anal skin tag with a narrow base in the right posterior position. She had no palpable mass or nodularity on digital rectal exam. Colonoscopy was normal, and she underwent an exam under anesthesia with excision of the skin tag. Grossly, the tag measured 7.0 x 5.2 x 3.8 cm.

Results/Outcomes: On microscopic examination, there were portions of squamous mucosa with dilated lympho-vascular structures and spindle cells with wispy collagen and perivascular lymphoid aggregates consistent with cellular angiofibroma. Immunohistochemical staining was positive for D2-40 (dilated lymphatics in subepithelial stroma), CD34 (endothelial cells and spindle tumor cells), ER (estrogen receptor), SMA, Desmin, Bcl2 and Ki-67 ( < 2%). Cytogenetic analysis using Fluorescent in situ hybridization (FISH) was positive for Loss of 13q (including RB1) (45%), consistent with cellular angiofibroma (Figure 1). There were no overt myxoid changes, necrosis, adipocytic component, or sarcomatous dedifferentiation. On routine outpatient follow up, the wounds were well healed.

Conclusion/Discussion: Anal skin tags represent one of the most common findings on rectal exams. Atypical presentations may conceal rare neoplasms or pathologies. This case signifies the importance of histopathologic evaluation and surgical excision to exclude more aggressive pathology and guide appropriate management.

Figure
Squamous mucosa with dilated lympho-vascular structures and a uniform, short, spindle cells in an edematous stroma with wispy collagen, with perivascular lymphoid aggregates (H&E). Immunohistochemical staining was positive for ER, SMA, and Desmin. Cytogenetic analysis using FISH was POSITIVE for Loss of 13q (including RB1)