Answer: Adenosarcoma

Histology: The tumor consists of tubular glands with cleft-like spaces. The papillary fronds are covered by a simplified columnar epithelium with occasional cells showing tubal metaplasia. The architecture of the fronds resembles a phyllodes tumor of the breast. The epithelium is typically bland and carcinoma is not by definition identified in these tumors. The mesenchymal component of the tumor is similar to that of a low-grade spindle cell sarcoma or low grade endometrial stromal sarcoma; however, high grade sarcoma can be present. In this tumor you can see the very characteristic periglandular stromal hypercellularity; this glandular cuffing is a characteristic of adenosarcoma. Sarcomatous overgrowth was not encountered in this tumor, but is present in about 10% of adenosarcomas and is said to occur when the sarcomatous component makes up great than 25% of the tumor.

Discussion: The main differential diagnosis for an adenosarcoma is a benign polyp. Polyps, however, lack the phyllodes architectural pattern that is characteristic of adenosarcomas. Further, polyps lack the periglandular stromal hypercellularity and nuclear atypia seen in adenosarcomas. Adenofibromas, which are also in the differential, are exceedingly rare. The stroma in an adenofibroma is less cellular with no stromal condensation around the glands. In contrast to endometrial stromal sarcomas (ESS), the glandular component is essential to the diagnosis of adenosarcoma. Although an ESS may entrap glands at its periphery it is very rare to find them throughout the tumor and the architecture of an ESS is very different from an adenosarcoma.