#00066489

In a 56-year-old female with metastatic ovarian carcinoma, peritoneal fluid cytology showing signet ring cells suggests metastatic mucin-producing adenocarcinoma. A signet ring cell is characterized by abundant intracellular mucin that pushes the nucleus to the cell periphery, giving the cell a ring-like appearance with the eccentric nucleus forming the “signet.” Microscopically, these cells have pale or clear vacuolated cytoplasm and a crescent-shaped peripheral nucleus. Signet ring cells are classically associated with Signet Ring Cell Carcinoma of the stomach but may also be seen in carcinomas of the ovary, breast, colon, urinary bladder, and lung. Their presence in peritoneal fluid indicates advanced metastatic disease and usually reflects aggressive tumor behavior.