Atypia in pulmonary cytology: Morphologic spectrum and causes

Abstract

Background The term “atypical” has had a long history of usage in cytology but has had variable definitions and usage. Most commonly the term was used to indicate a degree of cytomorphologic abnormality greater than that clearly due to reactive or reparative changes but not associated with a high concern on the part of the cytopathologist that a malignancy is present. The Papanicolaou Society of Cytopathology System for Reporting Respiratory Cytology provided a foundation for using the category “Atypical” along with the category “Suspicious for Malignancy” to categorize the spectrum of morphologic changes ranging from those which are clearly benign to those that are clearly malignant. The two intermediate categories of “Atypical” and “Suspicious for Malignancy” have characteristic recommendations resulting in clinical utility for both categories. Conclusion The Papanicolaou Society of Cytopathology System for Reporting Respiratory Cytology represents a useful system with defined intermediate categories of Atypical and Suspicious for Malignancy.

The World Health Organization Reporting System for Lung Cytopathology

“…The main causes of an "Atypical" categorization include intrinsic characteristics of the targeted lesion, the expertise of the operator, technical issues related to obtaining and preparing the material, and the experience of the pathologist who is interpreting the specimen [17,18]. All cellular elements of the respiratory tract including squamous cells lining the buccal mucosa and oropharynx, metaplastic squamous cells, respiratory columnar cells, terminal bronchiolar, or alveolar lining cells and pulmonary macrophages can demonstrate architectural and cellular atypia [19,20].…”

“…2). It is recommended clinical and imaging findings are reviewed before categorizing a specimen as "Atypical" [5,18]. Imaging studies can help differentiate between a localized and a diffuse and/or bilateral disease process.…”

“…A specimen categorized as "Suspicious for malignancy"' demonstrates some cytopathological features suggestive of malignancy but with insufficient features either in number or quality to make an unequivocal diagnosis of malignancy. The category "Suspicious for malignancy" is generally used in respiratory cytopathology to indicate a degree of uncertainty regarding the diagnosis of malignancy and offers a risk stratification for a Malignant diagnosis [2,4,18]. This category is often used when there is insufficient quality or quantity of cellular material in an adequate specimen for a definite diagnosis of malignancy.…”

The rationale for the development and publication of the World Health Organization reporting systems for cytopathology and a brief overview of the first editions of the lung and pancreaticobiliary systems

“…Typically, the expertise of the proceduralist, the targeted lesion's characteristics and ease of access, the manner in which the specimen material is handled, and the experience of the reporting pathologist all affect the "Atypical" reporting rate. 22,23 Categorization as "Atypical" is often related to reactive changes, including metaplasia and hyperplasia, infectious changes particularly those related to viral infections, acute respiratory distress syndrome, and changes after chemotherapy and radiotherapy. Correlation with clinical, microbiological, and imaging findings is required; and, if discrepant, further investigation is recommended.…”

“…Categorization as “Atypical” is often related to reactive changes, including metaplasia and hyperplasia, infectious changes particularly those related to viral infections, acute respiratory distress syndrome, and changes after chemotherapy and radiotherapy. Correlation with clinical, microbiological, and imaging findings is required; and, if discrepant, further investigation is recommended 21,23 . “Atypical” rates are reported as 3%–5%, and the ROM in a small number of published studies ranges from 50% to 60% 18,20,24 …”