Endobronchial ultrasound fine‐needle aspiration biopsy of pulmonary non–small cell carcinoma with subclassification by immunohistochemistry panel

Abstract

With the introduction of new treatment modalities and guidelines, it is important to subclassify primary pulmonary non-small cell carcinoma (NSCCA). Subsequent treatment and testing is dependent on accurate subclassification. Endobronchial ultrasound fine-needle aspiration (EBUS FNA) is used for primary evaluation and diagnosis, and can provide a cell block for ancillary testing. EBUS FNA cases from primary pulmonary NSCCA with an immunohistochemical (IHC) panel performed on a cell block with concomitant surgical pathology biopsy were analyzed. Cell block preparations underwent an IHC panel including monoclonal antibodies for napsin A (nap-A), thyroid transcription factor (TTF-1), p63, and cytokeratin 5/6 (CK5/6). A total of 81 cases from 81 patients were identified. Of these, 69 cases (85%) were provided a specific diagnosis of adenocarcinoma (ADCA) or squamous cell carcinoma (SCCA) on the EBUS FNA. In 12 cases (15%), a diagnosis of NSCCA, not otherwise specified was provided. For specific subclassifications, there were 35 ADCA cases, 34 SCCA cases, and 12 NSCCA, not otherwise specified cases. For ADCA, nap-A showed granular cytoplasmic staining and TTF-1 nuclear staining. For SCCA, CK5/6 showed cytoplasmic staining and p63 nuclear staining. Surgical pathology concomitant material was present in 29 of 81 cases with 18 correlations and 11 noncorrelations. With new treatment guidelines for patients with primary pulmonary NSCCA, specific diagnosis is increasingly important. EBUS FNA with cell block provided a specific subclassification of NSCCA in 85% of cases when used in conjunction with a specific IHC panel including nap-A, TTF-1, CK5/6, and p63.