title: Immunohistochemical staining on fine needle aspiration biopsy-cell block specimens in the differential diagnosis of lung cancers.
abstract: BACKGROUND
  Fine needle aspiration biopsy [FNAB] is used extensively in the clinical work-up of radiologically detected lung lesions. However, categorisation of lung cancer by computed tomography guided FNAB alone is limited by overlapping morphological features.
  
  
  OBJECTIVE
  To examine further the utility of immunohistochemical panel of antibodies to thyroid transcription factor [TTF-1], synaptophysin, chromogranin A [CgA], cytokeratin-pan, cytokeratin-7 [CK-7], cytokeratin-20 [CK-20], leucocyte common antigen [LCA], and carcinoembryonic antigen [CEA] in cytologic cell block samples in the differential diagnosis of lung cancer.
  
  
  METHODS
  Twenty-nine FNABs of newly diagnosed cases of lung cancer were studied. Immunohistochemistry was done on paraffin embedded cell block sections using Dako monoclonal antibodies.
  
  
  RESULTS
  Morphological diagnosis of non-small cell carcinoma (NSCLC) was made in 22/29 [76%] and small cell carcinoma in 7/29 (24%) cases. Five of the seven (71.4%) cases of small cell carcinoma were CgA+/TTF-1+, 14.3% [1/7] were CgA+/ synaptophysin+/TTF-1-negative. In one case, LCA positivity lead to the diagnosis of non-Hodgkins lymphoma. The NSCLC was categorised further into well differentiated 11/22 [50%], moderately differentiated 7/22 [31.8%] and poorly differentiated 4/22 [18.2%] cases. Cytokeratin-pan positivity in squamous cell carcinomas [n=15] was seen to be related to cellular differentiation. All the three cases of adenocarcinoma were CK-7+/CK-20 negative. In one case with large cell carcinoma, CgA-positivity lead to recategorisation as large cell neuroendocrine carcinoma.
  
  
  CONCLUSIONS
  Our results suggest that the proposed panel of immunohistochemical markers might help further classification of lung carcinomas even in small FNAB material and permit more consistent patient enrollment for trials with targeted treatments.
authors.affiliation: Department of Pathology, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India. ritukumar71@yahoo.com
authors.forename: Ritu
authors.initials: R
authors.lastname: Kulshrestha
authors.forename: V K
authors.initials: VK
authors.lastname: Vijayan