KRAS G12C lung adenocarcinoma with hypertrophic pulmonary osteoarthropathy: no recurrence after lobectomy

What happened, in summary

A 52-year-old man was referred for a tumor shadow in the right upper lung. He also had painful swelling in his hands, feet, knees, and lower legs, making it hard to wear shoes or grip objects. Exam showed clubbing of the fingers and toes, and imaging showed periosteal thickening, a pattern consistent with hypertrophic pulmonary osteoarthropathy related to lung cancer. Chest x-ray and CT revealed a 6 cm right upper-lobe mass with enlarged right hilar lymph nodes. PET-CT showed strong uptake in the lung tumor and mild uptake in the hilar nodes, tibias, and ankles. He was clinically staged cT3N1M0 / Stage IIIA and underwent right upper lobectomy. Final pathology showed acinar-predominant lung adenocarcinoma, pT3N0M0 / Stage IIB. Molecular testing detected KRAS G12C, and PD-L1 expression was below 1%. His joint pain improved quickly after surgery; he could walk on postoperative day 1, his chest drain was removed on day 5, and he was discharged on day 8. After discharge, he no longer needed NSAIDs, physical therapy, or other treatment for the joint symptoms. Grip strength improved from severely impaired levels before surgery to 40.9 kgf on the right and 32.9 kgf on the left at 3 months. At 1 year, there was no evidence of cancer recurrence, and hand x-rays showed improvement in periosteal thickening despite no adjuvant chemotherapy. Before surgery, blood tests also showed inflammation and elevated carcinoembryonic antigen, while rheumatoid factor and anti-CCP antibody were negative, making a primary inflammatory arthritis less likely. The rapid improvement after tumor removal supported the cancer-related nature of the joint syndrome.