Case Report: A 35-year-old female patient, G1 P1 D1 married since six years complained of "something coming out per vaginum" since 4-5 months. She also had a history of amenorrhea since two months and menorrhagia five to six months ago.

On examination, her vitals were stable.On per speculum examination, a large mass, approximately 11 cm in size, arising from the vagina with multiple necrotic areas was seen.

Her hemoglobin was 7gm%, which after transfusion of three pints of blood rose to 13 gm%.

RADIOLOGICAL FINDINGS:

A plain and contrast enhanced CT scan of the abdomen & pelvis was done. The coronal and sagittal reconstructed images revealed a large 10x 6 x 5 cms heterogeneously enhancing mass lesion in relation to the vaginal wall, extending cranially up to the level of the cervix and pushing the bladder neck anteriorly and laterally. It was not seen separate from the levator ani muscle. Posteriorly, it was in relation to the anal canal. A large component of the lesion was pedunculated (Figs.1, 2)

An MRI of the pelvis was also done. Post contrast T1WI scans revealed a 10x 6 x 5 cms, soft tissue mass lesion arising from the medial wall of the vagina on the left side and shifting the urethra to the periphery .(Fig.3)

T2 weighted sagittal images revealed high signal intensity within the tumour.The soft tissue planes between the mass and the urethra were effaced. The mass was seen to abut the pubic symphysis anteriorly. and extend superiorly up to the bladder neck.(Fig.4)

Coronal T1W STIR images demonstrated well, the relationship between the mass, the urinary bladder, urethra and the uterus.(Fig.5)

Axial T2 weighted images revealed that the mass displaced the neck of the urinary bladder laterally and demonstrated its relationship with the obturator internus muscle and the ischio-rectal fossa .No extension of the mass was seen in the ischiorectal fossa. (Fig.6)

Invasion of the levator ani muscles was noted on axial T2 and Fat suppressed T1 images (Figs.7,8).

A trans-perineal resection of this retrovaginal mass was performed and the gross specimen was sent for histopathology.

Pathologic findings : The gross specimen showed the mass to be gray-white and unencapsulated with few congested areas. On cut surface, it appeared homogenous and gray-white in colour.

Histopathology findings: The frozen section showed an unencapsulated tumour with myxoid matrix with many thin walled proliferating blood vessels and spindle cells. The cells lacked nuclear atypia and abnormal mitoses. Focal areas of necrosis were seen. There was no adjacent tissue infiltration. A diagnosis of an aggressive angiomyxoma was made. (Figs11,12)

DISCUSSION:

The term aggressive angiomyxoma was coined by Steeper and Rosai in 1983 for a morphologically distinctive, slowly growing myxoid neoplasm that occurs chiefly in the genital, perineal and pelvic regions of adult women. Despite its bland histologic features it has a propensity for local recurrence.

These lesions predominantly affect women in the reproductive age with a peak incidence during the 3rd decade of life. The female to male ratio is more than 6:1, but this tumour has increasingly been recognized as arising in the inguinal region, along the spermatic cord or in the scrotum or pelvic cavity of men. In women, the vulvar region is the most common site of involvement and may be initially misdiagnosed clinically as a Bartholin's cyst, perineal cyst or as a hernia. Although slowly growing, these lesions aggressively infiltrate the perivaginal and perirectal soft tissue.

Pathologic features:- Grossly, angiomyxomas are soft, partly circumscribed or polypoid. On cross section, they have a gelatinous appearance and range in size from a few centimeters to 20cm or more. Most have a lobulated appearance. Although some areas of the tumour may be sharply marginated, others show adherence or infiltration into the surrounding soft tissues.

Microscopically the tumour is composed of widely scattered spindle and stellate shaped cells with ill defined cytoplasm and variably sized thin or thick walled vascular channels in a myxoid stroma that is rich in collagen fibres and like other richly myxoid tumours often contains foci of haemorrhage.Mitotic figures are rare or absent and are not atypical.

Imaging studies

Ultrasonography shows a mass that is hypo echoic or appears frankly cystic.

Angiography shows a generally hyper vascular mass.

CT shows a hypo attenuating mass. The low attenuation at unenhanced CT is consistent with a myxoid matrix, high water content within the mass or both. The tumor tends to grow around the structures of the pelvic floor without penetrating the muscularis of the vagina or rectum. It shows a marked tendency to displace rather than invade perineal structures.

MR imaging shows very high signal intensity of the mass on T2-weighted images. This onT2weighted MR images may reflect the myxomatous stroma of these tumors. The enhancement of T1-weighted MR images after administration of gadolinium is related to the vascularity of aggressive angiomyxoma (AAM).

Both CT scans and T2-weighted MR images show the tumor to have a 'swirling internal architecture'. The cause of this appearance is not clear but may relate to the fibrovascular stroma that develops in tumors that are stretched as they protrude through the pelvic diaphragm.

No evidence of gross fat is seen within the mass, which distinguishes this tumor from other fat-containing tumors that also occur in the pelvis of women. The combination of these radiologic findings and the patient's symptoms related to a space-occupying lesion within the right pelvis make AAM the most likely diagnosis.

CT and MR imaging can accurately reveal whether a tumor traverses the pelvic diaphragm. This determination is critical to choosing the surgical approach either perineal, abdominal or both - comprehensive enough to avoid leaving residual tumor.

Differential Diagnosis:-

1)Angiomyofibroblastoma : This tumor also arises from the subcutaneous tissues of the vulva, vagina and rarely the scrotum.The lesion assumes a myxoid appearance as is found in aggressive angiomyxoma but has numerous thin walled vessels with perivascular hyalinisation. An aggressive angiomyxoma has a much higher risk of recurrence than angiomyofibroblastoma which is cured by local excision.
2) Pelvic fibromatosis show areas of typical fibromatosis on histopathology.
3) Others like myxoid liposarcoma and myxofibrosarcoma require pathologic differentiation.

Treatment
Surgical excision is the primary treatment for AAM. Although the tumor is histologically benign, locally aggressive behavior and high recurrence rates require complete excision wherever possible. The appearance of AAM on MR images is valuable in the identification of characteristic features of this tumor, evaluation of tumor extent, and planning of surgery. Recurrence rates of 36%-72% have been reported. Incomplete resection is acceptable because AAM is a benign tumor and because, in some cases, complete resection has high surgical morbidity and can threaten fertility in a patient population that is composed of mainly women who are in their child bearing years. Radiation therapy or chemotherapy is unlikely to be helpful, as patients with AAM demonstrate low mitotic activity. Long-term follow-up with CT and, preferably, MR imaging is recommended, since recurrences have been reported several years after first excision.