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.

Molecular testing on serous effusion: An update

Cytological examination of the effusion fluid provides valuable information regarding the presence of malignancy. At times, it is challenging to diagnose malignant cells in serous effusion. The various ancillary techniques are available to solve the problem including immunocytochemistry, DNA ploidy, and multicolored flow cytometry. At present, the molecular tests on the effusion sample are of growing interest. The effusion sample is rich in cells and cell-free fluid that contains free DNA, cytokines, and extracellular vesicles. Molecular tests in effusion sample not only provide a diagnosis of malignancy but can also give valuable information that may be essential for the individualized therapy, management, and prognostic assessment. In this paper, we reviewed the application of the different molecular tests in the effusion sample.

Approach to Diagnostic Cytopathology of Serous Effusions

Collection of most serous fluids from various effusions is a relatively simple procedure. Because of this, serous fluids are commonly submitted for pathologic examination including cytopathologic evaluation by various clinical institutions. As a consequence, even a general pathology laboratory which may not have expertise with highly trained cytopathologist would be confronted with serous fluids for cytologic evaluation. However, cytopathologic evaluation of serous fluids is complex as compared to evaluation of fine needle aspiration cytology. This signifies the fact that all pathologists, irrespective of subspeciality cytopathology training and level of subspeciality expertise, should be conversant with the diagnostic challenges and pitfalls of effusion fluid cytology. Although, majority of effusions are due to reactive and non-neoplastic etiologies, cancer is one of the causes of an effusion as a manifestation of advanced cancer. Detecting neoplastic cells in effusion specimens in most of clinical settings is related to the advanced status of the disease, which usually is equivalent to incurable stage. Thus, interpretation of cytopathology as positive for cancer cell is highly critical in planning the trajectory of the clinical management with an obvious negative impact of false positive interpretation. Apart from cancer, effusions may be secondary to hemodynamic pathologies such as heart failure, hypoalbuminemia, cirrhosis etc. in addition to the different inflammatory conditions including parasitic infestations, bacterial, fungal, or viral infections, and other non-neoplastic etiologies including collagen diseases. Due to the cytomorphologic overlap of reactive mesothelial cells with malignant cells, general cytologic criteria for diagnosis of malignancy in single cells cannot be applied in most of the effusion specimens. This challenge is further amplified because of surface tension related phenomenon which ‘round up’ the cells after exfoliation in serous fluids. As a result, the native shapes of cancer cells cannot be a guiding feature. Thus the cytomorphologic features of cancer cells in serous fluids may not be same as seen in routine cytopathology of exfoliative, brushing, and fine-needle aspiration specimens. The cancer cells may continue to proliferate after exfoliation in the nutrient rich effusion fluids and may form proliferation spheres. It is crucial to consider these factors when interpreting effusion cytology. Amongst malignant effusions, adenocarcinomas are the most common cause of metastatic cancers, but almost any type of malignancy including melanomas, hematopoietic neoplasms, sarcomas, and mesotheliomas may involve serous cavities. The interpreter must be aware of the wide range of the cytomorphologic appearances of reactive mesothelial cells in effusion fluids. It is essential to understand these and other nuances related to effusion fluid cytology. Understanding potential pitfalls during various stages from processing to application of ancillary studies would increase the diagnostic accuracy and minimize atypical interpretations and false positivity.

Diagnostic pitfalls in effusion fluid cytology

Effusion fluid cytology has propensity for both false positives (in up to 0.5%) and false negatives (in up to 30%) results. Methodical approach from collection step to final interpretation stage could prevent both false positives and false negatives, if the interpreter is familiar with various factors responsible for diagnostic pitfalls in effusion fluid cytology. For this discussion, these factors are categorized as mentioned below: Surface tension-related alterations in cytomorphology Improper specimen processing Many faces of reactive mesothelial cells, overlapping with those of cancer cells Proliferation-related features Degenerative changes, such as nuclear hyperchromasia and cytoplasmic vacuolation Unexpected patterns and unusual entities.

The panorama of different faces of mesothelial cells

All effusions in serous cavities represent a pathologic processes secondary to inflammatory, neoplastic, hemodynamic, or mechanical/traumatic etiologies. This elicits reactive changes in the extremely sensitive mesothelial cells lining the serosal surfaces. The result is hypertrophy and hyperplasia which lead to broad changes with a wide range of morphological appearances. These reversible alterations may resolve entirely after the recovery of underlying pathology. Under the tertiary care situations, neoplastic effusion specimens are encountered more frequently. Although some non-neoplastic pathologic process may demonstrate a few diagnostic features, cytologic evaluation of malignant effusions usually show diagnostic malignant cells. However, the most versatile mesothelial cells demonstrate a very wide cytomorphological spectrum secondary to reactive challenges. These mesothelial cells are usually referred to as ‘reactive mesothelial cells’. In addition other terms such as reactive mesothelial proliferation, reactive mesothelial hyperplasia, irritated mesothelial cells, activated mesothelial cells, hyperplastic mesothelial cells, hypertrophic mesothelial cells, and proliferative mesothelial cells. Rarely atypical mesothelial cells, although not recommended, is used inadvertently. Although there is a lack of general agreement defining these terms, some of these including atypical mesothelial cells, should not be preferred. With reference to this CMAS series, usually favored term ‘reactive mesothelial cells’ is preferred. The size of reactive mesothelial cells range from 15 to 30 µm (but may be up to 50 µm). These polyhedral cells with variable amount of cytoplasm and enlarged nuclei may show variation in sizes and shapes with conspicuous nucleoli. Bi- and multi-nucleation is frequent. Cohesive groups of mesothelial cells as sheets and three dimensional groups may be present. Some floridly reactive mesothelial cells with hyperchromatic enlarged nuclei with prominent nucleoli and scant cytoplasm may resemble malignant cells. This astonishingly wide morphological spectrum of reactive mesothelial cells is a significant interpretation challenge in effusion fluid cytology. Methodical interpretation approach with appropriate knowledge about this wide spectrum is important aspect in diagnostic cytopathology of effusion fluids.

Eosinophilic pleural effusion in an eleven-year-old boy

Pleural effusion fluid with ?10% eosinophils may be seen in 5-16% of exudative pleural effusions. Its association with helminthic infestation is reported in the literature. This patient with left-sided eosinophilic pleural effusion was a referred case from another hospital and treated initially as parapneumonic. With inadequate response to antibiotics and a markedly high IgE level praziquantel was started. This resulted in rapid disappearance of symptoms, decrease in the eosinophil count, and radiological improvement. After exclusion of parapneumonic, tuberculosis, autoimmune disease, and malignancy, a trial of antihelminthics should be considered an option. This may spare unnecessary investigations.

A case of coinfection of a pediatric patient with acute SARS-COV-2 with MIS-C and severe DENV-2 in Mexico: a case report

Background COVID-19 cases have been increasing since the epidemic started. One of the major concerns is how clinical symptomatology would behave after coinfection with another virus. Case presentation In this case report, a pediatric native patient from Estado de Mexico (EDOMEX), MEX had severe DENV-2 and acute SARS-CoV-2 at the same time. The clinical features were severe thrombocytopenia, secondary septic shock, cerebral edema, pericardial effusion, fluid overload that exhibited bipalpebral edema in all four extremities, hemophagocytic lymphohistiocytosis (HLH), coronary artery ectasia (CAE), multisystemic inflammatory syndrome in children (MIS-C), and probable COVID-19 pneumonia or acute respiratory distress syndrome (ARDS) that triggered patient intubation. The patient presented unusual symptomatology according to the literature. After 15 days of intubation and 15 more days under surveillance, he was released without respiratory sequelae and without treatment after major clinical improvement. Conclusion The aim of this manuscript is to present clinical challenges that coinfection may cause in pediatric patients, even though COVID-19 in children does not tend to be as severe as in other sectors of the population.

Role of liquid-based cytology and cell block study of pleural fluid in the evaluation of cases of malignant Pleural effusion with special reference to immunohistochemistry

Introduction: Lung cancer is the most common primary tumor associated with malignant pleuraleffusion (MPE). In this study, we aim to use cell remnants for cell block preparation after performingliquid-based cytology (LBC) of effusion fluid. Immunohistochemistry was helpful to evaluate thosecases having diagnostic dilemmas in LBC and cell block. Method: It was a cross-sectional,prospective, single institution-based study, conducted in the department of Pathology incollaboration with the Department of Respiratory Medicine IPGMER & SSKM Hospital, from January2018 to June 2019 in the institution. Result: Most of the study population were in between the agegroup of 51 to 60 years with male predominance and with fever and cough being the predominantsymptoms. Liquid-based cytology was positive for malignancy in 58% of cases and suspicious ofmalignancy in 22% of cases of malignant pleural effusion and it had 95.35% sensitivity, 58.82%specificity in diagnosing malignant pleural effusion.LBC was done followed by cell block preparationsare studied further by Immunohistochemistry. Discussion: Morphological features were betteridentified by the cell block method when compared to LBC. Multiple sections can be obtained forspecial stain or IHC study which bridges the gap between cytology and histology.