lung cancer is the most common cancer worldwide and is the leading cause of death in many countries . in the past , primary bronchopulmonary carcinomas were classified as non - small cell lung carcinoma ( nsclc ) and small cell neuroendocrine carcinoma . with the introduction of new treatment modalities , the identification of epidermal growth factor receptor ( egfr ) positive nsclc permits the use of tyrosine kinase inhibitors ( tki ) . also , the recognition of squamous cell carcinoma ( scc ) is important because if this subset of lung carcinoma patients is given bevacizumab , then it may lead to serious pulmonary bleeding . most patients with lung carcinoma present with clinically advanced disease , and fine needle aspiration cytology ( fnac ) may be the only available diagnostic specimen and also the only material available for molecular studies necessary for current therapeutic decision making . it is well documented that cytomorphology and immunohistochemistry ( ihc ) are useful in further categorization of nsclc . in centers where ihc is not readily accessible , a limited panel of antibodies can be used to categorize the tumor . in this study , we used a limited panel of antibodies to classify nsclc diagnosed based on fna from lung lesions . fine needle aspirates from patients with lung carcinoma with a morphological diagnosis of nsclc over a period of 5 years were studied . in 23 cases , ihc was performed ( blinded to the clinical data ) for thyroid transcription factor-1 ( ttf-1 ) , cytokeratin 7 ( ck7 ) , cytokeratin 20 ( ck20 ) , tumor protein p63 , and chromogranin a. ihc was performed manually on representative 4-m sections cut from formalin - fixed paraffin - embedded cell blocks using commercially available monoclonal antibodies . dehydrated tissue sections for immunocytochemistry were treated with 3% hydrogen peroxide in methanol for 10 min to block endogenous peroxidase and heated in 0.01 m citrate buffer ( ph 6.0 ) in a microwave for epitope retrieval . sections as well as smears were incubated with primary antibody for 1 h at room temperature . detection system used was envision - flex ( dako , glostrup , denmark ) according to manufacturer 's instructions . detection was achieved using diaminobenzidine ( dab liquid ; dako , carpinteria , ca , usa ) . the antibodies used in the study were ttf-1 ( monoclonal , 8g7g3/1 ; 1:50 dilution ; dako , carpinteria , ca , usa ) , ck7 ( monoclonal , ov - tl 12/30 ; 1:50 dilution ; dako , glostrup , denmark ) , ck20 ( monoclonal , ks 20.8 ; 1:50 dilution ; dako , glostrup , denmark ) , p63 ( monoclonal , 4a4 ; 1:50 dilution ; dako , glostrup , denmark ) , and chromogranin a ( monoclonal , dak - a3 , 1:50 dilution , dako , glostrup , denmark ) . standard , appropriate histologic tissue was used as positive control and the negative control was run by omission of primary antibody . ck7 was positive in 12 of the 14 ttf-1 positive tumors and 5 of the ttf-1 negative tumors . ck20 and chromogranin was negative in both the ttf-1 positive and negative tumors [ table 1 ] . all the 14 ttf-1 positive tumors were primary lung tumors , 12 being nsclc and 2 being scc . five of the 9 ttf-1 negative tumors were metastatic tumors from endometrium , kidney , and head and neck region ( two ) , and in one tumor , the primary site was unknown . four of the 9 ttf-1 negative tumors were morphologically nsclc and were clinically considered to be primary lung tumors . three of these tumors stained positive for ck7 but negative for ck20 and p63 , and one case was negative for all the immunomarkers . two tumors that were positive for p63 and ck7 but negative for ttf-1 were metastatic from the head and neck region . the final diagnosis in the 23 nsclc was primary lung nsclc in 18 and metastatic tumor in 5 . the distinction of subgroups of nsclc may be challenging on cytological material based on morphology alone . this distinction is very important in the proper management as the egfr - directed tkis , erlotinib and gefitinib , are effective in patients with adenocarcinoma having the egfr mutation , while patients with scc should not be given bevacizumab because of the risk of fatal pulmonary hemorrhage . the determination of the egfr mutation is not available in all the cytology laboratories , and thus , we proposed to use a minimal panel of antibodies for further characterization of the nsclcs . we found that by using ttf-1 , ck7 , ck20 , chromogranin , and p63 , we were able to identify primary lung tumors and further type them as scc . ttf-1 and p63 immunostaining has been successfully applied to cytological material to facilitate pathological differentiation between small cell carcinoma and poorly differentiated pulmonary scc . ttf-1 has been found to be the most specific marker for adenocarcinoma with 60% sensitivity and 98% specificity , in comparison to napsin a that has a sensitivity of 83% and specificity of 98% . also , it has been shown that p63 had 95% sensitivity and 86% specificity for scc , while cytokeratin 5/6 had 53% sensitivity and 96% specificity . napsin a and p63 have been proposed as the most cost - effective panel of antibodies for differential diagnosis of primary lung adenocarcinoma from scc . due to availability of ttf-1 in our laboratory , we proposed to study this marker and found it equally effective . 2011 ) , by using a four - antibody panel ( ttf-1 , desmocollin-3 , p63 , and napsin a ) , were able to refine lung cancer classification in fnac cell blocks , remarkably reducing the percentage of unclassified nsclc from 36% to 14% . to conclude , we found that using a limited panel of antibodies , we were able to classify nsclc . though not ideal , this panel of antibodies offered the best discrimination and helped separate primary tumors and also classify them into adenocarcinomas or scc .
background : newer treatment modalities require subtyping of non - small cell lung carcinomas ( nsclc ) . 
 morphological differentiation is often difficult and various immunohistochemical ( ihc ) panels have been used to maximize the proportion of accurately subtyped nsclc.aim:the aim of this study was to subtype nsclc on fine needle aspirates ( fna ) using a minimal antibody panel.materials and methods : cell blocks from 23 fna samples with a morphological diagnosis of nsclc were taken . 
 ihc was evaluated ( blinded to clinical data ) for thyroid transcription factor-1 ( ttf-1 ) , cytokeratin ( ck)7 , ck20 , and tumor protein p63.results:ttf-1 was positive in 14 and negative in 9 cases . 
 the p63 was positive in two cases each of ttf-1 positive and negative tumors . 
 ck7 was positive in 12 of the 14 ttf-1 positive tumors and 4 of the ttf-1 negative tumors . 
 ck20 was negative in all . 
 all the 14 ttf-1 positive tumors were primary lung tumors , 12 being nsclc and 2 being squamous cell carcinoma . 
 five of nine ttf-1 negative tumors were metastatic tumors from endometrium , kidney , and head and neck region ( two ) , and one was an unknown primary . 
 four of the nine ttf-1 negative tumors were morphologically nsclc and were clinically considered to be primary lung tumors . 
 three of these tumors stained positive for ck7 but negative for ck20 and p63 , and one case was negative for the immunomarkers.conclusion:use of limited ihc panel helps categorize primary versus secondary tumors to the lung . 
 the p63 is a useful marker for detecting squamous cell carcinoma . in countries where antibodies are not readily available , 
 using a limited ihc panel of ttf-1 , p63 , and ck7 can help further type nsclc lung tumors .