adenocarcinoma

Adenocarcinoma is a malignant tumor that arises from glandular epithelium or from cells that have acquired gland-forming or mucus-producing abilities. It forms abnormal glandular structures and can occur in many organs where glandular cells are present. It is the most common histologic type of cancer in several sites, including the lung, colon and rectum, breast, pancreas, stomach, and prostate.

In the lung, adenocarcinoma is the most common type of non-small cell lung cancer and frequently arises in the outer regions of the lung. In the colon and rectum, colorectal adenocarcinoma develops from gland-forming cells and is linked to the process of adenomatous polyp progression. In the breast, the majority of cancers are adenocarcinomas, including ductal and luminal subtypes. Pancreatic and stomach adenocarcinomas originate from ductal or gastric glandular epithelium, and prostate adenocarcinoma arises from prostatic glands.

Histologically, adenocarcinomas are characterized by malignant glands with irregular architecture and often mucin production. Immunohistochemistry and molecular testing help determine the tumor’s origin and guide therapy; markers such as TTF-1 can indicate lung origin, while other profiles may point to colorectal or breast origin. Common molecular alterations in adenocarcinomas include mutations and rearrangements that inform targeted therapies or immunotherapy, depending on the tumor site.

Staging follows established systems such as the TNM classification, and prognosis varies by site and stage. Treatment is tailored to location and extent: localized disease may be managed with surgical resection and possibly adjuvant chemotherapy or radiotherapy; advanced disease commonly requires systemic chemotherapy, targeted therapies, immunotherapy, or combinations thereof. Early detection and site-specific management are important factors influencing outcomes.