Answer: Embryonal rhabdomyosarcoma

Histology: Microscopically there is a loose stroma with numerous blood vessels and inflammation. Occasionally, entrapped benign glands can be seen. Focal areas with increased cellularity contain primitive spindled cells with hyperchromatic, pleomorphic nuclei. Numerous mitotic figures are present in these areas.

Discussion: Embryonal rhabdomyosarcoma is the most common malignant neoplasm of the vagina in infants (“sarcoma botryoides”). It is important to note, however, that it can occur in the cervix in adults. Microscopically there is a cambium tumor cell layer of rhabdomyoblasts under the epithelium. In addition, dense collections of rhabdomyoblasts may be seen within the loose myxoid stroma. Immunohistochemical staining for desmin highlights the rhabdomyoblasts and a Ki-67 proliferation index is increased in these areas. In embryonal rhabdomyosarcoma, glands can become entrapped and are not part of the neoplasm. In adenosarcoma, the glandular component is part of the neoplasm and the stroma dislays hypercellular “cuffing” around the benign glands. Endometrial stromal sarcomas are more uniformly and densely cellular proliferations of bland endometrial-type stromal cells and are reactive with CD10. Myxoid leiomyosarcomas lack a cambium layer and are more uniformly hypocellular.