Endometrial stromal sarcomas with true papillae and pseudopapillae

Most endometrial stromal sarcomas (ESSs) have a characteristic histologic appearance and the diagnosis is easily made based on the typical growth pattern, vascular pattern, and cell type. However, there are several variants, which may result in problems in diagnosis and consideration of other neoplasms. We describe 3 examples of a hitherto not well-described phenomenon in uterine ESS, namely the formation of papillae or pseudopapillae. The patients were aged 37, 42, and 52. In 2 cases, the neoplasms were typical ESSs apart from the presence of pseudopapillae; in 1 case the pseudopapillae were present throughout the neoplasm and in the other this was a focal finding involving 10% of the tumor. In the third case, there was a true papillary component involving sex cord-like elements within an ESS and a prominent papillary architecture in the metastatic tumor which developed 7 years later resulted in initial misdiagnosis as a serous adenocarcinoma. This report emphasizes the potential for ESSs to form pseudopapillae or true papillae, which may involve areas of usual ESS or sex cord-like elements. The formation of papillae or pseudopapillae may result in diagnostic difficulty and confusion with other neoplasms, especially if the phenomenon is widespread.