Uterine adenosarcoma with sarcomatous overgrowth: a case report with cytology of overgrown poorly differentiated sarcoma and immunohistochemical identification of epithelial microinvasion.

In this report, we describe a case of adenosarcoma of the uterine corpus with overgrown and poorly differentiated sarcoma. The patient was an 80-year-old Japanese woman with abnormal genital bleeding. The endocervical biopsy showed undifferentiated carcinoma, and a cytologic examination at that time revealed the presence of cell types ranging from dispersed spindle to round atypical cells, suggestive of mesenchymal origin. The resected uterus had a polypoid mass in the corpus of the uterus and a solid white mass with the appearance of frank malignancy in the endocervix. The phyllode pattern was evident in the polypoid lesion and a diagnosis of adenosarcoma with sarcomatous overgrowth was made. The epithelial component was atypical with occasional microinvasion, which mimicked rhabdomyoblasts, but was easily identified as microinvasion by positive staining for epithelial, but not myogenic, markers. This case stresses the importance of the cytologic smear in the identification of frank sarcoma in an adenosarcoma, and it furthermore highlights the usefulness of immunohistochemistry in the distinction of epithelial microinvasion from rhabdomyogenic differentiation.