Abstract :
Introduction: Majority of lung cancer presents at an advanced unresectable stage, emphasizing the
diagnosis on cytological specimens like EBUS-TBNA. This study was aimed to subtype lung carcinomas
on EBUS-TBNA specimens on smears and cell blocks (CB) and to assess the utility of limited panel ICC
towards this subtyping.
Materials and Methods: This is both retrospective and prospective study done on total of 142 cases for
two and half years. The samples from either lung or mediastinal lymph nodes diagnosed as lung carcinoma
on cytomorphology in correlation with clinico – radiological features were included. Extrapulmonary
metastatic tumors, lymphomas and malignancies other than carcinomas were excluded. The cytologic
material (EBUS-TBNA smears and CB) was obtained by EBUS TBNA procedure done on lung lesions
and/or mediastinal lymph nodes and stained with required stains. All cases were first classified as small
cell carcinoma (SCC) and non small cell carcinoma (NSCC) on cytomorphology as per 2004 WHO
classification. NSCC was then further subtyped. ICC with TTF1/p63 antibodies was applied on NSCC
and synaptophysin on SCC/neuroendocrine tumors. Napsin A was applied on p63/TTF1 negative cases.
The results were expressed in frequencies and percentages.
Result: On cytomorphology alone, 25 of 142 cases (17.6%) were classified as SCC and 117 cases
(82.4%) as NSCC. NSCC was further subtyped on cytomorphology (smears CB) into definitive (squamous
cell carcinoma [SqCC]/adenocarcinoma [ADC]) v/s favouring (favouring SqCC/ ADC/ adenosquamous
carcinoma) v/s not otherwise specified (NOS) in 41 (35.1%) v/s 33(28.2%) v/s 43(36.7%) cases
respectively. Immunostains TTF1/ p63 and napsin A applied on possible 86 NSCC cases reduced NOS to
9.3 %. Synaptophysin confirmed all 20 cases of SCC and 1 large cell neuroendocrine carcinoma (LCNC).
Overall in 142 cases, limited panel ICC reduced NSCC-NOS to 11.9%.
Conclusion: Subtyping of lung carcinoma on EBUS- TBNA samples is feasible. Preparation of cell block
allows application of ICC. A limited panel ICC comprising p63, TTF1 and synaptophysin can classify in
majority of cases with napsin A useful as secondary antibody in p63, TTF1 negative cases. IntroductionThe
aim of this study was to know the efficacy of cytomorphology (smears and CB) in subclassification of lung
carcinomas on E BUS-TBNA samples & to assess the value of addition of limited panel ICC as an adjunct
to cytomorphology in this subtyping.
Keyword :
Lung cancer, EBUS-TBNA p63, TTF1, Synaptophysin, Cell block.