Epidermal growth factor receptor mutated oligometastatic adeno-squamous lung cancer transformation to small cell lung cancer

A 66-year-old non-smoker was diagnosed with stage IIIB, epidermal growth factor receptor (EGFR) mutated, squamous cell lung carcinoma. Treatment included chemotherapy, 35 fractions of radiotherapy and later Gefitinib for 3.5 years. On progression he developed a solitary brain and liver lesion. The brain lesion was excised and histology revealed adenocarcinoma of a lung primary. Afatanib was commenced for 1 further year. At the second time of progression re-biopsy identified small cell carcinoma. He completed four cycles of Carboplatin and Etoposide however deteriorated on completion of chemotherapy. EGFR directed treatment is associated with improved patient outcomes. It has been suggested that EGFR mutated squamous cell carcinoma more likely represent mixed morphology or poorly differentiated adenocarcinoma. Patients with oligometastatic progression can be treated beyond progression however the addition of a local therapy may be required. Small cell transformation is described as a rare mechanism of resistance to EGFR treatment as in our case.