Which of the following is a marker for small cell lung carcinoma?

Bombesin is a peptide that can act as a neurokinin and is associated with small cell lung carcinoma (SCLC). SCLC is a type of lung cancer characterized by small, round cells that grow quickly and are often associated with neuroendocrine features. One of the aspects of SCLC is its production of neuroendocrine markers, including bombesin.

Bombesin serves as both a hormone and a neurotransmitter, and its presence can help indicate the neuroendocrine differentiation of tumors, making it particularly relevant for small cell lung carcinoma. The connection between bombesin and SCLC is significant because it underscores the neuroendocrine nature of the cancer, which impacts its biological behavior and treatment strategies.

In contrast, other options like CA 19-9, CA 15-3, and CA 125 are tumor markers associated with other types of cancers. CA 19-9 is primarily linked to pancreatic cancer, CA 15-3 is associated with breast cancer, and CA 125 is most commonly known for its relevance in ovarian cancer. Therefore, bombesin stands out as the specific marker relevant to small cell lung carcinoma.