Introduction to the second edition of 'Diagnostic Cytopathology of Serous Fluids' as CytoJournal Monograph (CMAS) in Open Access.

Serous fluids are excessive accumulation of fluids in a serous cavity as effusion. However, traditionally this area also covers cytopathologic evaluation of washings of these cavities including pelvic/peritoneal washing. This is the introductory review article in series on this topic with the application of simplified algorithmic approaches. The series would be compiled finally as a book after minor modifications of individual review articles to accommodate the book layout on the topic as second edition of 'Diagnostic Cytopathology of Serous Fluids' book. The approach is primarily directed towards detection of neoplastic cells based on morphology alone or with the help of various ancillary tests, including commonly applied immunocytochemistry to be interpreted as second foreign population with application of SCIP (subtractive coordinate immunoreactivity pattern) approach in effusion fluid tapings. As the role of molecular pathology tests is increasing, this component as ancillary testing will also be covered as applicable. Because a picture and sketches are worth a thousand words, illustrations and figures are included generously even at the risk of moderate repetition. The clinically important serous cavities include peritoneal cavity, pericardial cavity, and two pleural cavities. The primary topic of this series is specimens from these cavities as effusion fluids and washings including cytopathologic evaluation of peritoneal/pelvic washing. It is expected that some readers may not read the entire series or the final book from beginning to end, but refer to the individual review articles and chapters sporadically during their clinical practice. Considering this practical limitation, some brief repetition may be observed throughout the book. Some of the important themes will be highlighted as italicized and bolded text for quick reference. Dedicated articles/chapters are assigned for technical and other reference material as appendices. Tables, algorithms, sketches, and combination of pictures are included generously for quick reference. Most of the illustrations are attempted to be labeled appropriately with arrows and other indicators to avoid equivocation, especially for beginners in the field. This introductory review article describes general details under the following three broad headings: Histology and general cytology of serous cavity lining Effusion (general considerations) Ancillary techniques in brief.