A case of epidermal growth factor receptor tyrosine kinase inhibitor effectiveness in epidermal growth factor receptor mutation-positive squamous cell carcinoma

A 71-year-old non-smoker woman was admitted to our hospital because of left front chest pain. A computed tomography scan showed a large mass of >7.0 cm in the lower left part of the lung and multiple organ metastases in the liver, brain, bone, and left adrenal gland. Pathological analysis of a resected specimen obtained by bronchoscopy revealed keratinization. In addition, p40 was positive and thyroid transcription factor-1, synaptophysin, CD56, and chromogranin A were negative by immunohistochemistry. Programmed cell death ligand 1 expression was 1%–10%, and exon 19 deletion was detected. We diagnosed the patient with stage IVB lung squamous cell carcinoma and administered osimertinib. Osimertinib was later replaced with afatinib because of grade 3 skin rash. Overall, the size of the cancer was decreased. Furthermore, her symptoms, laboratory data, and computer tomographic findings markedly improved. In summary, we experienced a case of epidermal growth factor receptor–positive lung squamous cell carcinoma that was responsive to epidermal growth factor receptor tyrosine kinase inhibitors.