Epidermal Growth Factor Receptor Mutation in a Patient with Squamous Cell Carcinoma of the Lung: Who Should Be Tested?
An otherwise healthy 64-year-old Caucasian man presented with worsening right inguinal pain since 3 months. He had a 30 pack-years smoking history until 25 years ago. A computed tomography scan showed a 7 × 7.5-cm mass infiltrating the right psoas muscle, a right-sided hilar lung lesion, enlarged ipsilateral mediastinal lymph nodes and a 4.5 × 3-cm adrenal mass. A bronchoscopic biopsy confirmed a poorly differentiated carcinoma, positive for p63, CK5/6 and negative for TTF-1 (thyroid transcription factor-1) on immunohistochemical staining (fig. ). The pathology report stated a poorly differentiated squamous cell carcinoma (SCC) of the lung, and systemic therapy was initiated. Unfortunately, the patient progressed after two cycles of first-line chemotherapy with carboplatin and paclitaxel and subsequently received palliative radiotherapy with 50 Gy for the psoas metastasis and the primary tumour. In addition, an epidermal growth factor receptor (EGFR) mutation analysis from the initial tumour material revealed an activating point mutation in exon 21 (p.L858R). The EGFR tyrosine kinase inhibitor (TKI) erlotinib was started resulting in a partial remission after 8 weeks of therapy, and the patient became asymptomatic and unrestricted in his physical activity (fig. ). Twenty-two months later, he developed multifocal progression with lung and liver metastases. A bronchoscopic rebiopsy showed small nests of undifferentiated tumour cells with weak immunoreactivity of some tumour cells for p63, CK5/6 and also positivity of some tumour cells for TTF-1, suggesting a mixed squamous/glandular immunophenotype (fig. ). Third-line chemotherapy remained unsuccessful, and the patient died 33 months after initial diagnosis.