c-Myb Overexpression in Cytology Smears of Tracheobronchial and Pulmonary Adenoid Cystic Carcinomas

Aims: Adenoid cystic carcinoma (AdCC) is a malignant epithelial neoplasm that occurs rarely in the lower respiratory tract (LRT). AdCC at various sites is associated with the novel fusion transcript MYB-NFIB, along with the overexpression of the Myb protein. The expression of the Myb protein in AdCC of the LRT has not been evaluated much. Study Design: Cases of AdCC of the LRT diagnosed on cytology or histology were retrieved from our institutional archives. c-Myb expression was analyzed on immunocytochemistry/immunohistochemistry (ICC/IHC) and was correlated with clinicopathological parameters. Results: Twenty-three samples of AdCC originating from the LRT were included in the study. Four cases were diagnosed on cytology, 3 of which had corresponding histology specimens. The remaining 19 cases had either biopsy or resection. Most of the patients presented with endobronchial mass. The mean age was 49.4 years and a male predominance was seen. ICC and IHC for c-Myb showed positivity in 75 and 59% of the cases, respectively. Western blot was used to validate IHC results. Conclusion: AdCC of the LRT is rare and hence poses diagnostic difficulty. Cytology smears can be utilized for c-Myb ICC. The presence of c-Myb immunopositivity in most cases may possibly make Myb a diagnostic biomarker and a therapeutic target for personalized treatment.