[450] Cytological Identification of Adenocarcinoma of the Lung with Minimal Use of Immunohistochemistry. Can We Meet the Challenge?

Congli Wang, Yajue Huang, Varsha Manucha. Temple University Hospital, Philadelphia, PA

Background: Adenocarcinoma is the most common histologic type of lung cancer. To address recent advances in therapy of lung adenocarcinoma IASLC/ATS/ERS has put forward a new adenocarcinoma classification. This requires a multidisciplinary and strategic management of tissue for molecular and immunohistochemical studies. For the first time, the new classification addresses an approach to small biopsies and cytology in lung cancer diagnosis. It has been recommended that the use of immunohistochemistry at the time of primary evaluation should be restricted to the use of a two stain panel and to preserve as much tissue as possible for potential molecular markers, thereby laying more emphasis on morphological categorization. Unfortunately, morphology often is bypassed in favor of immunohistochemistry in routine pathology. In this study we attempted to see how far we can correctly categorize non small cell carcinomas without the use of immunostains.
Design: 50 cases of cytologically diagnosed non small cell type lung carcinomas were blind reviewed by one of the author (VM) with an attempt to categorize them into adenocarcinoma and squamous cell carcinoma based on cytological features alone. The findings were compared with the initial diagnosis. Results of immunohistochemistry if used for the initial diagnosis was documented.
Results: On retrospective blind review, 26 cases were categorized into adenocarcinoma and 14 cases were categorized as squamous cell carcinoma. There were 10 cases that were called non small cell carcinoma. In comparison at the time of initial diagnosis, 24 cases were called non small cell carcinoma (including the 10 cases on blind review). In 24 cases immunohistochemistry was used for further subtyping at the time of initial diagnosis and use of 2 stains (p63 and TTF-1) amongst multiple stains, were helpful in a definitive categorization. Of the 10 non small cell carcinoma called at the time of initial diagnosis and at the time of blind review, 4 turned out to be squamous cell carcinoma. There were 2 cases that could not be categorized even on resection specimen; thereby highlighting that use of large panels of immunohistochemical stains does not provide an advantage over routine light microscopic diagnosis.
Conclusions: When attempted, at least 90% cases of adenocarcinomas can be identified based on cytological features alone and with use of a two stain immunostains panel. Poorly differentiated squamous cell carcinoma is more likely to be called a non small cell carcinoma.
Category: Cytopathology

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 73, Wednesday Afternoon


Close Window