Mucinous adenocarcinoma arising from chronic perianal fistula-a multidisciplinary approach

Abstract

Mucinous adenocarcinoma (MA) is a rare entity. Indeed, the pathogenesis of fistula-associated perianal MA is still controversial. Due to the lack of informed evidence regarding this malignancy, no guidelines have been established concerning diagnostic and treatment strategies. The aim of this article is to report our experience and outcomes after three cases of large perianal MA treated in our center. From our retrospective chart review, we identified three male patients with chronic perianal fistula-in-ano who progressively developed perianal MA, confirmed by pelvic magnetic resonance (MRI) and histopathological examination performed on biopsy. We hereby, in accordance with the Surgical CAse REport (SCARE) guidelines, describe the management and further follow-up of each patient. The three patients underwent preoperative chemoradiation therapy, followed by ischioanal abdominoperineal resection (APR). Perineal reconstruction was needed in every case, using a vertical rectus abdominis myocutaneous (VRAM) flap and, punctually, a left fasciocutaneous flap was used too. Also, two of three patients completed the treatment with adjuvant chemotherapy. Neither recurrences nor distant metastases have been observed during the follow-up in both cases that finished the multimodal treatment. MA arising from chronic perianal fistula has an indolent growth with locoregional aggressiveness and a high risk of local recurrence. Therefore, although an ischioanal APR remains the surgical treatment of choice, an aggressive multimodal approach combining preoperative chemoradiation and adjuvant chemotherapy may achieve favorable effectiveness and promising response rates.

Keywords: Mucinous adenocarcinoma (MA); abdominoperineal resection; chemoradiotherapy; fistula-in-ano; perianal fistula (PF).

Figure 1

Physical examination, magnetic resonance imaging (MRI) and abdominoperineal resection. (A) Perianal swollen area, with several external openings; (B) MRI shows hyper signal in T2, suggesting mucinous adenocarcinoma (arrow); (C) abdominoperineal resection, surgical specimen; (D) perineal reconstruction with VRAM flap. VRAM, vertical rectus abdominis myocutaneous.

Figure 2

MRI T2-weighted images in (A) axial and (B) coronal plane showing the tumor involving the left elevator muscle of the anus and the mesorectum on either sides (arrows), piercing into the intersphincteric space, as well as the left ischioanal fossa; (C) biopsy from pelvic mass shows lakes of mucin (*) and tumor glands invading surrounding squamous epithelium (arrows) from fistulous tract (200×, H&E); (D) perineal reconstruction.

Figure 3

Diagnosis, histological examination, and postoperative result. (A) Oblique coronal MRI T2-weighted image showing a large mucinous tumor arising from perianal fistula, measuring 49 mm × 42 mm × 71 mm; (B) biopsy from the lesion showing lakes of mucin (*) and intervening stroma (arrows) showing chronic inflammatory changes (H&E, 400×); (C) tortuous glands with lakes of mucin consistent with mucinous adenocarcinoma (H&E, 200× and 400×); (D) perineal reconstruction using VRAM flap. MRI, magnetic resonance imaging; VRAM, vertical rectus abdominis myocutaneous.