Appreciation of Pattern in Diagnosis of Lung Adenocarcinoma from Cytology Specimen: Our Experience with Fine Needle Aspiration Cytology and Cell Block in a Resource Constraint Setup

BACKGROUND AND AIMS: Advent of personalised treatment needs correct diagnosis of lung adenocarcinoma with its molecular subtyping. Minimal use of special stain or immunohistochemistry (IHC) in small specimens save material for molecular testing. Various histologic patterns in adenocarcinoma (ADC) subtypes have different prognostic implications and current recommendation is to describe these patterns in small specimens. Aim of this study was to diagnose adenocarcinoma from cytology specimens depending on adenocarcinoma pattern on fine needle aspiration smears and cell blocks. We also studied the additional role of cell blocks as a platform for special stain and IHC. MATERIALS AND METHODS: Conventional smears and cell block (CB) preparation were examined from transthoracic CT guided FNA samples of suspicious lung malignancy cases. Clear defining architectural pattern and cytomorphological features in favour of adenocarcinoma were evaluated and mucin stain and IHC were used as and when required. RESULTS: A total of 86 cases were included in this study, of which 83 cases were diagnosed as adenocarcinoma, 52 (62.5%) showed clear cut evidence of adenocarcinoma from smears and CBs. CB morphology alone aided the diagnosis in 12. Various ADC patterns in combination or alone were appreciated in these 64 cases. Sixteen needed mucin stain and 3 needed IHC for diagnosis. Forty one were ADC with solid pattern of which 39 showed high nuclear grade. CONCLUSION: Adequately cellular FNA smears and corresponding cell blocks of optimal quality can aid effectively in diagnosing adenocarcinoma and appreciating its pattern. Therefore, it would minimize the need for special stain and/or IHC with preservation of more material for molecular testing.