[1771] Evaluation of Cyto-Histologic Agreement for Defining Histologic Subtype of Lung Carcinoma.

Shin W Lai, Mauro A Saieg, William R Geddie, Scott L Boerner, Gilda C Santos. University Health Network, Toronto, ON, Canada; University of Toronto, ON, Canada

Background: The differential therapeutic efficacy and toxicity of targeted therapies has made differentiation of non-small lung cancer (NSCLC) into squamous cell carcinoma (SCC) and adenocarcinoma (AC) subtypes mandatory. The use of immunohistochemistry (IHC) in core needle biopsies has been recently reported to improve accuracy. This study aimed to review lung fine needle aspirates (FNAs) to assess the overall impact of IHC in subtyping NSCLC and the agreement between the final cytological and surgical diagnoses.
Design: An electronic search retrieved all cases with lung FNAs and subsequent surgical resection during the period between 2001 to 2009. All metastatic tumors, non epithelial neoplasms, inflammatory, negative or suspicious for malignancy, and unsatisfactory results were excluded from the analysis. Only NSCLC cases with cytological and corresponding surgical specimen were selected. Overall agreement between cytological and surgical diagnoses was assessed for cases with specific cytology subtypes. NSCLC cases without subtyping were stratified by year and the cell block (CB) slides were reviewed to identify the reasons why subtyping was not stated. The number of cases in which IHC was performed, the antibodies used and the purpose of the assay were also tabulated.
Results: A total of 605 cytology cases were retrieved from the database. 433 (71.6%) cases had a final cytological diagnosis of either AC or SCC. In 172 cases, no subtypes were defined and were reported as NSCLC, NOS (not otherwise specified) (28.4%). The number of cases in this category has decreased since 2001, reaching the lowest rate in 2009 (17.4%). Among NSCLC cases cytology subtyped into AC and SCC, an agreement with surgical diagnosis was found in 377 (94.0%) cases. When stratifying the reasons for no subtyping, 40 cases had no CBs, 9 CB had no tumor cells, and in 28 cases IHC was performed but was not contributory. IHC was performed in 157 cases, of which 56 were done specifically for subtyping NSCLC. The median number of antibodies used was 3. TTF-1 was the most frequently (91.1%) used antibody, followed by CK7 and HMWK (44.6%).
Conclusions: Specific subtyping can be achieved in a high proportion of lung FNAs with high level of agreement with surgical diagnosis. The percentage of NSCLC with no further subtype has been decreasing in recent years. The use of IHC increased the accuracy of the cytological diagnosis, and TTF-1, CK7 and HWMK were the most used antibodies.
Category: Pulmonary

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 280, Tuesday Afternoon


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