Squamous cells in effusions: A study of 24 cases

Abstract

Malignant squamous cells in serous effusions are rare. We present our experience with squamous cell carcinoma (SqCC) and benign squamous cells in effusions. Specimens were retrieved from our database using search codes as "squamous" within the final diagnosis under various serous effusions. Twenty-nine specimens were recovered, and 5 of those were excluded. Of the 24 specimens, 3 were duplicates; therefore, only the first specimen from each was included for a final tally of 21 specimens. Specimens were from pleural fluid (n = 16, 76%), pericardial fluid (n = 2), pelvic fluid (n=2), and peritoneal fluid (n = 1). Nineteen were SqCC (primary sites: 7 lung, 2 uterine cervix, 2 larynx, 2 anus, 2 esophagus, 1 tongue, 1 mandible, 1 skin, 1 vulva), and 2 patients had benign squamous cells only (1 from a ruptured esophageal adenocarcinoma and 1 from a nonmalignant esophageal rupture). In SqCC cases, a round-oval cell with dense cytoplasm was the predominant cell type (n = 12) followed by undifferentiated cells (n = 4), polygonal-type cells (n = 2), and fiber-type cells (n = 1). Of the SqCC specimens, 12 (63%) showed varying degrees of keratinization. Other features in SqCC cases included refractile rings (89%), keratin pearls (53%), and vacuolated cytoplasm (42%). Herxheimer spirals were absent. Two benign cases showed polygonal cell morphology only. All patients with SqCC died shortly after fluid collection (range 2-313 days; mean: 58.1 days). Metastatic SqCC in serous effusions are rare, primarily arranged as single cells with rounded nuclei lacking visible nucleoli surrounded by a minimal amount of dense cytoplasm, and represent a dismal prognosis.