Fine needle aspiration cytology of low grade endometrial stromal sarcomas.

The cytomorphology of endometrial stromal sarcoma (ESS) has been described. However, almost all of the reports are about the high grade type according to the newly revised histopathologic criteria; the cytomorphology of low grade ESS (endolymphatic stromal myosis) has yet to be characterized. This paper reports on two cases of recurrent low grade ESS diagnosed by fine needle aspiration and confirmed histopathologically. The aspirates consisted of extremely cohesive tissue fragments of monotonous, small (8-9 microns), oval cells tightly woven in a metachromatic, extracellular matrix on Diff-Quik-stained smears. In Papanicolaou-stained smears the transparency allowed visualization of bland, normochromatic, oval nuclei as well as small arterioles transecting the tissue fragment, whereas the extracellular matrix became invisible. The metachromatic, extracellular matrix in the smears correlated with the reticular fibrillar network wrapping around individual tumor cells on tissue sections, one of the histopathologic criteria that separates low grade from high grade ESS.