Purpose or Case Report: A 17-month-old female presented with a one-month history of abnormal soft tissue protruding from the vaginal introitus.

The patient’s past medical history was significant for hemi-hypertrophy of the left lower extremity. Physical examination demonstrated normal external genitalia, with pink solid tissue protruding from the vagina posterior aspect, and mild associated white fluid discharge. Laboratory analysis revelaed a normal CBC, serum HCG and AFP.

An ultrasound examination of the pelvis demonstrated a heterogeneous echogenicity soft tissue mass with scant internal vascularity centered in the vagina and cervix, measuring approximately 4.0 x 2.3 x 2.5 cm.

The patient’s clinical and imaging findings were most concerning for malignancy, namely vaginal rhabdomyosarcoma, so consultation was requested from Pediatric Surgery and Oncology. As a result of these consultations, the patient was scheduled for vaginoscopy with biopsy under general anesthesia, as well as surgical port placement due to the high suspicion for malignancy. Also to be performed under the same anesthetic was a CT examination of the chest and MR examination of the pelvis.

Vaginoscopy revealed a “pebbly appearance” of the vaginal walls, which also reportedly “felt thickened” on digital exam. Multiple surgical biopsy specimens were obtained from the visibly abnormal areas.

MR examination immediately post biopsy showed circumferential mural thickening of the cervix and vagina, with a more prominent area of soft tissue thickening at the level of the vaginal introitus. The areas of mural thickening appeared T1 and T2 signal isointense with mild post-contrast enhancement and no evidence of abnormal restricted diffusion. No focal mass was identified. CT examination of the chest was normal.

Histopathologic analysis revealed a benign lesion composed of a relatively small number of spindle cells embedded in a loose fibrous stroma. No significant numbers of mitoses or atypia were observed, including in the lining squamous epithelium. These features were most consistent with a fibroepithelial stromal polyp.

In light of the pathology findings, the port implant was removed, and the patient has since undergone surveillance vaginoscopy examinations.

This case illustrates MRI findings of a rare benign condition which may mimic vaginal rhabdomyosarcoma on the basis of clinical and ultrasound findings. MRI demonstrating an absence of aggressive features may help to suggest this rare differential consideration.
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