PERIANAL LEIOMYOMA: CASE REPORT

Case Report A 49-year-old female patient was seen in the Coloproctology outpatient clinic, complaining of a painless nodule in the perineal area for the past 3 years, without associated symptoms. On physical examination, a 3 cm nodule was palpated in the left anterior perineum, between the rectum and vagina. In March 2024, a pelvic floor MRI was performed, with the report describing a solid nodular image, with well-defined borders, located in the left anterolateral aspect of the intersphincteric plane in the perianal region, without cleavage plane with the anal canal wall, and external left sphincter muscle bulging, measuring approximately 3.4 × 2.6 × 2.5 cm. The diagnostic impression was indeterminate, although gastrointestinal stromal tumor (GIST) was considered as a differential diagnosis. During surgery, an incision was made in the left lateral perineum, and the lesion was completely resected with clear margins. No invasion of the rectum or vagina by the lesion was observed during surgery. The patient had a good postoperative recovery with complete healing. The resected specimen was sent for histopathological examination, which described a perineal nodule, with elastic consistency, measuring 3.4 × 2.4 × 1.8 cm, and was immunohistochemically positive for fumarate hydratase, desmin, and smooth muscle actin. The final diagnosis was a benign mesenchymal neoplasm: leiomyoma.

Discussion Leiomyoma is a benign soft tissue tumor originating from mesenchymal cells derived from smooth muscle. The most common occurrence of this tumor is in the uterus, while it is rare in the anorectal region. The pathogenesis is not well defined. The prevalence is 1 in every 3,000 rectal tumors, and the malignancy rates gradually increase with age. It typically presents in the age range of 30-69 years and may present with symptoms like rectal bleeding, tenesmus, proctalgia, and changes in bowel habits, or it may be asymptomatic, depending on its size. Due to the lack of specific symptoms, diagnosis is often delayed. The standard and potentially curative treatment for anorectal leiomyomas, without invasion of adjacent organs as seen in this case, is surgical excision with complete resection and clear margins to avoid recurrence.

Conclusion This case highlights the importance of differential diagnosis, early intervention, and follow-up to detect potential recurrences and/or malignant transformation.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
25 April 2025