What happened, in summary

A 76-year-old man was found to have two small nodules in the right upper lung. Because their appearance was not typical of cancer, the lesions were followed with imaging. Over 4 months both nodules shrank dramatically without treatment, and follow-up was stopped after they were considered nonmalignant. Two years later, a nodule reappeared in exactly the same location and had grown to about 19 mm. PET imaging showed high metabolic activity, and biopsy diagnosed squamous cell carcinoma. He underwent right upper lobectomy with lymph-node dissection. Pathology showed a rare basaloid squamous cell carcinoma of the lung, with immune-cell infiltration around the tumor. The unusual course suggested spontaneous regression followed by regrowth. His course underscores that even a lung lesion that shrinks or nearly disappears without treatment can later prove malignant and may still require continued surveillance.