[1789] Clinical Utility of Immunohistochemistry for the Diagnosis of Lung Squamous Cell Carcinoma in Biopsy and Cytologic Specimens

M de Peralta-Venturina, D Phan, R Parakh, T Fennell, M Amin, A Marchevsky. Cedars Sinai Medical Center, Los Angeles, CA; William Beaumont Hospital, Royal Oak, MI

Background: Oncologists are currently interested in distinguishing squamous cell carcinoma (SCC) from 'non-squamous' (non-SCC) lung cancer as histologic subtype is associated with efficacy and toxicity of emerging targeted or combination therapy regimens. SCC generally express CK5/6 and p63 while non-SCC stain for TTF-1 and Napsin-A. Desmoglein-3 (DSG3) is a recently described marker for SCC particularly for the lung.This study aims to evaluate the clinical utility of immunohistochemistry (IHC) using these antibodies in the distinction between SCC and non-SCC in small biopsy specimens.
Design: A total of 47 patients with resected lung SCC who had previous positive bronchial or core biopsy or fine needle aspiration (FNA) were identified from the files of 2 institutions. There were 13 bronchial biopsies, 23 core biopsies and 11 FNA. Formalin-fixed paraffin-embedded tissue sections of the biopsies or cell block were stained with p63 (Biocare), CK 5/6 (Cell Marque), DSG3 (Abcam), TTF-1 (Cell Marque) and Napsin-A (Leica). Double immunostaining technique was used for p63/CK 5/6 and TTF-1/Napsin-A. 20 lung adenocarcinoma biopsies were stained for comparison. The extent of staining was evaluated as 1+ to 3+ (<25%, 25-50% and >50%) and the intensity as 0 to 3+.
Results: Biopsies and FNA were diagnosed as SCC based on histomorphology in 97% and 72% of cases, respectively. The use of IHC identified all SCC in all types of biopsy material based on positivity with at least one squamous marker. p63 was the most sensitive antibody for SCC (98%) followed by DSG3 (94%) and CK 5/6 (85%). DSG3 membranous staining tended to be variable and patchy compared with p63 or CK 5/6. Four cases of SCC (8.5%) expressed TTF-1 while none expressed Napsin-A. Of the 20 adenocarcinoma biopsies, 8 (40%) showed rare faint p63 staining. None of the adenocarcinoma cases showed staining for CK 5/6 or DSG3. Sensitivity and specificity for the diagnosis of SCC using DSG3, CK 5/6 and p63 were 94% and 100%, 85% and 100% and 98% and 60%, respectively.
Conclusions: Immunohistochemistry on small biopsy material, particularly on FNA with adequate cell block, can provide a definitive diagnosis of SCC. Although p63 is the most sensitive, DSG3 and CK 5/6 have higher specificities for diagnosing SCC. A panel of 2 squamous markers (DSG3 and CK 5/6) and 2 adenocarcinoma markers (TTF-1 and Napsin-A) is useful in distinguishing SCC from non-SCC in small biopsy specimens.
Category: Pulmonary

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 247, Wednesday Morning


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