adenocarcinoma

Adenocarcinoma is a cancer that arises from gland-like cells — the kind that normally make and secrete substances such as mucus. In the lung, picture the small mucus-producing cells of the airways and air sacs turning malignant and trying, imperfectly, to form gland structures. This gland-forming habit is exactly what pathologists look for to name it.

It is the most common subtype of lung cancer today, and notably it is the type most often seen in people who have never smoked, as well as in younger patients and women. Adenocarcinomas usually grow toward the outer (peripheral) part of the lung rather than in the central airways, which is one reason they may not cause early cough or be visible on a basic chest X-ray.

Adenocarcinoma is the subtype most likely to carry treatable molecular drivers, such as EGFR mutations and ALK rearrangements. Because of this, guidelines strongly recommend molecular testing on adenocarcinoma tissue, since a positive result can open the door to oral targeted therapies that are often gentler and more effective than chemotherapy for those specific tumors.

On imaging, early adenocarcinoma can appear as a faint ground-glass shadow rather than a solid lump, which is part of why it can be subtle and why follow-up of such findings matters.