Which lung cancer is defined as a poorly differentiated tumor that cannot be classified as squamous or adenocarcinoma?

Prepare for your CVP and GI Pathology Exam. Study using flashcards and multiple choice questions with hints and explanations to excel in your test.

In lung cancer, when a tumor doesn’t show clear features of either squamous differentiation (like keratinization or intercellular bridges) or glandular differentiation (like mucin production or gland formation), it is categorized as a large cell carcinoma. This is a diagnosis of exclusion within non-small cell lung cancers. The cells are poorly differentiated and lack the recognizable patterns of squamous cell carcinoma or adenocarcinoma, even after immunohistochemical testing. Some cases may be further studied with stains to see if a definitive lineage can be identified, but if those tests remain non-definitive, the tumor is labeled large cell carcinoma. This distinguishes it from small cell carcinoma, which has a neuroendocrine phenotype and different morphology and markers, and from the other two main NSCLC types that have distinct architectural features.