Discussion

ACC is a rare malignancy of exocrine glands. The minor salivary glands are its most common location. They may also arise in other sites of the head and neck region, aerodigestive tract, breast, lungs, prostate and the female genitourinary tract. It usually occurs in the fifth or sixth decade of life and has a slight female preponderance.^{Reference Dillon, Chakraborty, Moskaluk, Joshi and Thomas1} Primary ACC of the lung constitutes only 0.1–0.2 % of all lung cancers. In the respiratory tract, they tend to occur centrally, in the trachea or central bronchi. They extensively invade inside and beyond the bronchial wall.^{Reference Qing, Zhou, Liu, Li, Deng and Ma2} Lung ACC manifests as a slow-growing mass, and clinical features are due to the mass lesion itself. Paraesthesia or pain occurs due to perineural invasion.^{Reference Spiro and Huvos3} ACCs have a low propensity for lymph nodal spread. Metastatic disease may occur in 40% of cases, with the liver, breast, bone or the brain the usual sites for distant spread.^{Reference Dillon, Chakraborty, Moskaluk, Joshi and Thomas1} Histopathology reveals tumour cells with angulated hyperchromatic nuclei, with minimal eosinophilic or clear cytoplasm. The original term ‘cylindroma’ is a reflection of cylindrical secretory cells with a hyaline stroma. Three growth patterns seen on histopathology are cribriform, tubular and solid.^{Reference Dillon, Chakraborty, Moskaluk, Joshi and Thomas1,Reference Azumi and Battifora4} IHC aids the histopathological diagnosis.^{Reference Qing, Zhou, Liu, Li, Deng and Ma2} Primary management is surgical. Definitive radiotherapy can be considered if surgery is not feasible. Post-operative radiotherapy may decrease local recurrences.^{Reference Spiro and Huvos3,Reference Balamucki, Amdur and Werning5} Metastatic disease shows low response rates to chemotherapy. There is no standard chemotherapy regimen, but, cisplatin has the strongest rationale.^{Reference Cerda, Sun and Vignot6} Targeted therapy specific to ACC requires further investigation, and drugs inhibiting the epidermal growth factor receptor (EGFR) pathway may have a role.^{Reference Mendes, Barroso and Campainha7}