High grade endometrial stromal sarcoma on thinprep

High grade endometrial stromal sarcoma (HGESS) is an uncommon malignancy recently re‐defined in the new WHO classification of endometrial stromal tumors. In this article, we discuss the differential diagnoses of metastatic HGESS in a fine needle aspiration (FNA) of a lymph node and compare the cytomorphology of HGESS in ThinPrep [(TP), Hologic Inc., Boxborough, MA] to conventional smears (CS). The patient had a history of stage I HGESS, status‐post supracervical hysterectomy without regional lymph node metastases. Her post‐operative course was complicated by pelvic fluid collections and enlarging para‐aortic lymph nodes. Diff‐Quik (DQ)‐stained and Papanicolaou (Pap)‐stained smears from a para‐aortic lymph node FNA demonstrated a cellular specimen with monomorphic population of plump to oval cells with scant, wispy cytoplasm in aggregates and as single cells. The nuclei showed fine chromatin and small inconspicuous nucleoli. Compared to the CS, HGESS cells in the TP showed similar cytological features, with the exception that the nuclei were slightly smaller, hyperchromatic, and the chromatin pattern was attenuated. In the absence of prior clinical history, the cytomorphology of metastatic HGESS in a lymph node can be difficult to differentiate from a lymphoma, a variety of metastatic spindle cell tumors or metastatic carcinoma. Immunohistochemical analysis and comparison with the primary tumor can be useful in proving the nature of the malignant cells. The cytomorphology of HGESS on TP correlated well in both single cells and aggregates when compared to CS. The differences noted were decreased nuclear size, nuclear hyperchromasia, and slightly attenuated nuclear detail on TP. Diagn. Cytopathol. 2015;43:756–762. © 2015 Wiley Periodicals, Inc.