Müllerian Adenosarcoma of the Urinary Bladder: Clinicopathologic and Immunohistochemical Features With Novel Genetic Aberrations

BACKGROUND: Müllerian adenosarcoma is a biphasic neoplasm most commonly occurring in the uterus and less frequently of the ovary. It has been rarely described to occur in other sites such as peritoneum and liver. PATIENTS AND METHODS: In this study, we report the clinicopathologic, immunohistochemical and molecular features of a primary Müllerian adenosarcoma of the urinary bladder in a 62-year-old woman. To our knowledge, this is the first report of detailed pathologic characterization of Müllerian adenosarcoma primary to the urinary bladder in the literature. RESULTS: Light microscopy showed a biphasic epithelial and stromal tumor with benign-appearing glands surrounded by densely cellular endometrial-type stroma that is densely cellular with increased mitotic figures. The stroma surrounding the glands was more cellular than the intervening areas, which were more loose and edematous. Immunohistochemistry staining revealed positive staining for Pax-2/8 within the glands, for positive CD10 and WT-1 within the spindle cell stroma, and for estrogen and progesterone receptors in both. Staining for desmin, GATA3, p63, and human papillomavirus was negative. Molecular analyses identified mutations in protein kinase B E17K, fms related tyrosine kinase 3 D835N, KRAS proto-oncogene, GTPase G12D, and HRAS proto-oncogene, GTPase G12S. These novel molecular aberrations have yet to be reported in the medical literature. X chromosome inactivation analysis revealed a clonal pattern in the stromal component and a nonclonal pattern in the epithelial component. Currently, the patient is disease/recurrence-free after regular follow-up of approximately 84 months. CONCLUSION: This case represents, to our knowledge, the first reported diagnosis of Müllerian adenosarcoma arising in the urinary bladder with extensive clinicopathologic, immunohistochemical, and molecular analyses.