Final answer:
Small round to oval cells that are highly malignant in the lungs indicate small cell lung cancer (SCLC), a rapidly progressing form of lung cancer most commonly caused by tobacco smoking.
Step-by-step explanation:
Small round to oval cells that are highly malignant are characteristic of a type of lung cancer known as small cell lung cancer (SCLC). This form of cancer is distinguished by its rapid growth and early spread to other organs. It is strongly associated with tobacco smoking, which is the most common cause of lung cancer and is known for its aggressive nature. SCLC comprises about 10-15% of all lung cancer cases and requires prompt and aggressive treatment, usually involving chemotherapy and radiotherapy. Diagnosis is typically confirmed through a combination of imaging tests, such as chest X-rays or CT scans, and biopsy samples.