title: Melanoma with signet-ring cells in a peritoneal effusion.
abstract: Melanoma may occasionally give rise to a malignant effusion and when this occurs it can present a challenging differential diagnosis. We present such a patient who developed a peritoneal effusion. Cytologic examination of the peritoneal fluid revealed individual malignant cells with prominent cytoplasmic vacuoles raising the possibility of a signet-ring cell adenocarcinoma. Immunohistochemical studies were indicative of a malignant melanoma. In this case we believe that the cytoplasmic vacuoles may be a degenerative phenomenon and as such may represent another mechanism for the development of a signet-ring morphology in malignant melanoma.
authors.affiliation: Department of Pathology, University of Iowa, Iowa City, USA.
authors.forename: T H
authors.initials: TH
authors.lastname: Niemann
authors.forename: P A
authors.initials: PA
authors.lastname: Thomas
mesh_terms: D001202:Ascitic Fluid / Q000473:pathology*; D018279:Carcinoma, Signet Ring Cell / Q000473:pathology*; D003937:Diagnosis, Differential; D017809:Fatal Outcome; D006801:Humans; D008297:Male; D008545:Melanoma / Q000473:pathology*; D008875:Middle Aged