Mullerian adenosarcomas are uncommon tumors of the female genital tract characterized by a synchronous proliferation of benign glands and sarcomatous stroma. In general, uterine Mullerian adenosarcomas are associated with a low risk of recurrence. The presence of "stromal overgrowth" (SO), historically defined by an estimate of the volume of sarcoma growing independently of epithelium, is associated with deep myometrial invasion, presence of heterologous elements, and poor outcomes. Very rarely, the stromal component can harbor foci resembling ovarian sex cord tumors (FROSCT). The aim of this study was to determine whether the presence of an extensive FROSCT component in Mullerian adenosarcomas has an impact on survival, akin to more typical types of SO. Six patients were included in this study. Age ranged from 39 to 71 yr. Five patients presented with uterine lesions (4 intracavitary, 1 isthmic), and 1 was located in the ovary. Tumors ranging in size from 2.5 to 19 cm were all diagnosed as Stage I. Morphologically, all had prominent FROSCT-like components that comprised 60% to 90% of tumor volume. Immunohistochemically, the FROSCT component was positive for CAM 5.2, vimentin, WT1, CD56, α-inhibin, calretinin, androgen and progesterone receptors, α-actin, and desmin. All patients are alive without disease at 26 to 102 mo. Compared with adenosarcomas with typical forms of SO, FROSCT overgrowth is low grade and not associated with recurrence or metastasis in this small series. Therefore, Mullerian adenosarcoma with extensive FROSCT should not be equated with SO.