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

Background: 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.

Methods: 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).

Results: 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.

Conclusions: 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.