Teaching Case

A 60-year-old female presented with complaints of perineal swelling for 1 year which was gradually increasing in size. The patient was also experiencing difficulty in micturition and defecation for the past week. The patient had undergone surgery for a pelvic mass 10 years before.

USG showed large hypoechoic solid-cystic lesion extending from the umbilicus to the pelvis. The lesion did not appear to invade surrounding structures. The ureter was seen coursing through the mass.

CECT showed large heterogeneously enhancing solid-cystic lesions extending till the aortic bifurcation superiorly. Inferiorly, the lesion was extending up to the right ischiorectal fossa displacing the rectum and the sigmoid colon without any signs of invasion. There was an extension into the vaginal vault, up to the labia majora. Anteriorly, the lesion was abutting the anterior abdominal wall. The lesion also caused displacement of small bowel loops laterally. Posteriorly, there was compression of the bilateral common iliac arteries by the lesion, without any signs of thrombosis.
There was no sign of invasion into surrounding structures.

There are few differential diagnoses of perineal soft tissue tumours in adult female patients.

Aggressive angiomyxoma (AAM) is ill-defined, mostly >5cm in size. It is locally invasive and tends to recur, however, distant metastases are not recorded. They grow slowly without invasion of the surrounding structures. [1, 3, 6]
Patients present with the complaints of perineal swelling, dysmenorrhoea or dyspareunia.
The true extent is often underestimated on physical examination, because the visible portion usually shows only a fraction of the deep involvement. [5]
CT demonstrates a large locally invasive pelvic tumour, which extends towards the ischiorectal fossa. It may be a well-defined, moderately enhancing mass, hypodense relative to muscle or it may be predominantly cystic with solid components. It is consistent with myxoid matrix, high water content within the mass or both. It does not show gross fat within the mass. [3, 5]

Angiomyofibroblastoma is a localised, well-circumscribed tumour, which usually measures <5 cm in size. It may show microscopic fat within and does not recur. [2, 4]

Fibroepithelial stromal polyps are relatively common benign lesions of the vulvovaginal region that may be multiple and are associated with pregnancy or exogenous hormone use. Local excision is usually curative. [5]

Myxoid leiomyoma is another pelvic tumour that can grow quite large. Myxoid change may be focal or involve the entire tumour and a helpful diagnostic clue is to identify an area of transition between the myxoid features and more-classic smooth muscle differentiation histologically. [5]

Differentiating these tumours on the basis of imaging findings is quite difficult as they all share the most imaging features. However, on the basis of clinical history (as in the case of fibroepithelial stromal tumour), the size of the lesion (as in the case of angiomyofibroblastoma) or presence of recurrence, it is possible to reach a conclusion. The final diagnosis is generally made by the biopsy.

The first line of therapy for AAM is surgery, but achieving negative resection margins is difficult because of the infiltrative nature and the absence of a defined capsule. Smaller tumours may be removed with wide, local excision, but larger, deep-seated tumours of the pelvis may require more extensive surgery with partial or complete resection of some pelvic organs. The prognosis is generally good. Recurrence rates range from 25-47% with 85% of those occurring within 5 years of initial surgery. [5, 7]

This patient had undergone surgery for pelvic mass 10 years back which was proven to be AAM histologically and again presented with a similar appearing lesion. Due to the extensive involvement of the lesion, the patient was declared non-operable.