Primary Vaginal Alveolar Rhabdomyosarcoma in an Adult Woman: A Case Report.

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children, but its occurrence in adults is exceedingly rare. Among its subtypes, embryonal RMS predominates in the female genital tract, whereas alveolar rhabdomyosarcoma (ARMS) is exceptionally rare at this site, with only isolated cases reported in the literature. We describe the case of a woman in her mid-40s who presented with abnormal vaginal bleeding and a friable polypoidal mass arising from the anterior vaginal wall. Magnetic resonance imaging demonstrated a well-defined lesion measuring approximately 28 × 23 × 13 mm, confined to the vaginal wall, without invasion of adjacent structures or evidence of nodal or distant metastasis. The patient underwent wide local excision of the lesion. Histopathological examination revealed a malignant small round cell tumor with an alveolar growth pattern, and immunohistochemistry confirmed the diagnosis of ARMS, showing strong nuclear positivity for myogenin and cytoplasmic positivity for desmin, with negative epithelial, lymphoid, and neural markers. Following multidisciplinary tumor board discussion, the patient was planned for adjuvant systemic chemotherapy with ifosfamide and adriamycin, followed by external beam radiotherapy (50 Gy in 25 fractions) and intracavitary brachytherapy boost (6 Gy in three fractions). Adult vaginal ARMS is associated with an aggressive clinical course and poor prognosis despite multimodal therapy. This case highlights the importance of considering RMS in the differential diagnosis of vaginal masses in adults and underscores the need for early diagnosis and multidisciplinary management in improving outcomes.