However, SCEVs are distinctive because they express little if any [Alpha]-smooth muscle actin and S100 protein or intermediate filaments other than cytokeratin and vimentin.
Thus, coexpression of CD34, CD99, and Bcl-2 without immunohistochemical or ultrastructural evidence of myofibroblastic differentiation is consistent with the origin of SCEVs from more primitive, less differentiated cells than other mixed tumors.
In recent years, an ever-widening spectrum of [CD34.sup.+] tumors has been described; some have features similar to those in SCEVs, and these [CD34.sup.+] tumors were considered in the differential diagnosis.
The origin of SCEVs has been proposed to be from a possible embryonic remnant. Although the embryologic development of the vagina is controversial, the hymenal ring appears to be derived from the urogenital sinus.[1,17,18] The greatest controversy exists on the relative contributions of the mullerian ducts and urogenital sinus to the development of the vagina.