Hyaline matrix material in high-grade endometrial stromal sarcoma diagnosed by fine-needle aspiration: case report

We present a case of a high-grade endometrial stromal sarcoma metastatic to the abdomen with an unusual extracellular hyaline matrix material seen on fine needle aspiration biopsy. The patient was initially diagnosed with a stage IIIA high-grade endometrial stromal sarcoma and had received four cycles of chemotherapy over the past year. She subsequently developed an abdominal mass that consisted of discohesive small cells with scanty cytoplasm on fine needle aspiration. On the Diff-Quik-stained smears, metachromatic, extracellular hyaline material was identified. This appeared on the Papanicolaou-stained smear as cyanophilic material and did not react with reticulin stain. This case emphasizes the importance to the cytopathologist of including endometrial stromal sarcoma in the differential diagnosis of hyaline matrix material.