What is the characteristic histology of small cell lung cancer?

Small cell lung cancer (SCLC) is characterized histologically by the presence of small round cells that have scant cytoplasm. This distinctive appearance, often referred to as "oat cell" morphology, results from the small size of these tumor cells, which can have very little cytoplasm relative to the nucleus. The nuclei are typically hyperchromatic with a high nuclear-to-cytoplasmic ratio, providing a hallmark feature of SCLC.

This histological presentation is critical in differentiating small cell lung cancer from other types of lung cancers. The small round cells often grow in sheets or clusters and can exhibit mitotic activity, which is an indicator of their high proliferation rate. Understanding this characteristic histology is vital for diagnosis and treatment planning in clinical oncology.

The other options depict histological features found in different lung cancer types or conditions: large atypical cells are more indicative of poorly differentiated cancers, fibrous tissue overgrowth suggests a desmoplastic reaction rather than a primary tumor feature, and keratinized squamous cells relate to squamous cell carcinoma. Thus, recognizing small round cells with scant cytoplasm as the defining feature of small cell lung cancer is crucial in the context of cancer diagnosis and treatment.