[1789] Utility of Ancillary Studies in the Classification of Lung Adenocarcinoma and Squamous Cell Carcinoma in Cytology Specimens.

Rebecca Ocque, Naobumi Tochigi, Paul Ohori, Sanja Dacic. University of Pittsburgh Medical Center, PA

Background: Histologic subtyping of non-small cell lung carcinoma (NSCLC) is becoming important because the efficacy and toxicity of new treatments for NSCLC highly depend on tumor histology. Majority of lung cancers are not surgically treated, and only limited tissue is available for diagnostic and molecular studies. The aim of this study was to assess the diagnostic accuracy of classification of lung adenocarcinoma (ADC) and squamous cell carcinoma (SQC) on cytology and biopsy specimens based on cytomorphology alone or in combination with ancillary studies when compared to resection specimens.
Design: 448 diagnostic preoperative cytology specimens (transthoracic CT-guided FNAs, bronchial brushings, and washings) of a primary lung ADC (263 cases; 59%) and SQC (185 cases; 41%) that underwent surgical resection at the Universitiy of Pittsburgh Medical Center between January 2000 and January 2010 were included in the study. Histologic classification of the tumor on the cytology and resection specimens, the results of histochemical (mucicarmine, PAS with diastase) and immunohistochemical (IHC) studies (cytokeratin (CK) 7, 20, 5/6; TTF-1, surfactant protein A, and p63) reported in the Pathology electronic records were documented. Classification accuracy of cytology specimens was defined as histologic concordance between the cytologic classification and the final surgical resection diagnosis. CK5/6 and p63 were used asIHC markers for SQC and TTF-1 and surfactant protein A were markers for ADC.
Results: The diagnosis of SQC was based more often on cytomorphology alone (75% SQC vs. 41% ADC)(P=0.001). More frequent use of IHC in cytology was noted after introduction of EGFR targeted therapies in clinical practice (14% ADC and 8% SQC before 2005 vs. 86% ADC and 89% SQC after 2005). Use of IHC resulted in increased diagnostic accuracy for ADC (56% before 2005 vs. 83% after 2005)(p=0.0001), but not for SQC (77% before 2004 vs. 74% after 2005)(p=0.7290). IHC reduced the number of ADC, but not SQC, classified as NSCLC. ADC showed high expression of CK7 (100%), TTF-1 (86%), surfactant A (81%) and PASD (80%). All of SQC were positive for CK5/6 and p63. Subsets of ADC and SQC were interpreted as positive for p63 and TTF-1 respectively.
Conclusions: Implementation of EGFR targeted therapies in lung cancer treatment resulted in increased use of ancillary studies for the classification of NSCLC. IHC appears to be useful in diagnosis of ADC, but not SQC. The panel of p63 and PASD may be help to exclude the squamous differentiation on diagnostically limited specimens.
Category: Pulmonary

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 281, Tuesday Afternoon

 

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