Occurrence of intercellular spaces (windows) in metastatic adenocarcinoma in serous fluids: A cytomorphologic, histochemical, and ultrastructural study

The application of cytomorphologic criteria to the examination of serous ef fusions allows the reliable diagnosis of malignancy in the majority of case s. One feature observed in tissue fragments previously thought to be indica tive of mesothelial origin is the presence of intercellular windows, presum ably due to long surface microvilli. In this study; however; we examined cy tologic preparations of 143 effusion and body-cavity washing specimens and noted distinct intercellular window formation within tissue fragments of ad enocarcinoma in 13% of the cases studied. Stains for mucicarmine, Alcian bl ue with hyaluronidase pretreatment, and periodic acid-Schiff following dias tase digestion on corresponding cell block material demonstrated that inter cellular mucin contributes to such window formation in greater thar? half o f these cases. Thus the presence of intercellular windows within tissue fra gments does not, in isolation, preclude the diagnosis of malignancy in sero us effusions. (C) 1999 Wiley-Liss, Inc.