Advanced Non-Small Cell Lung Cancer With ERBB2 and TP53 Mutations

What happened, in summary

A 53-year-old man who had never smoked developed cough, sputum, chest pain, and shortness of breath in November 2023. Imaging showed a right upper-lung tumor invading nearby mediastinal structures, additional tumors in both lungs, pleural fluid, multiple liver metastases, and extensive bone metastases. Fluid was drained from his chest to relieve his breathing difficulty.

Cancer cells in the pleural fluid supported a lung primary. The tumor had an unusual pattern in which TTF-1 and p40 were both expressed, suggesting features of both glandular and squamous differentiation rather than a straightforward conventional subtype. Molecular testing found an ERBB2 exon 20 mutation and a TP53 mutation. PD-L1 expression was reported as 0%.

He received 6 cycles of carboplatin and pemetrexed with the anti-angiogenic drug bevacizumab. Follow-up scans in December 2023 and February 2024 showed stable disease rather than further progression. After completing the initial 6 cycles, he moved to maintenance treatment with pemetrexed and bevacizumab. At the latest documented follow-up, he was in good condition and the cancer remained stable. The case illustrates how molecular testing and careful pathology review can help guide treatment when a lung cancer does not fit neatly into a single histologic category.