EGFR mutation identifies distant squamous cell carcinoma as metastasis from lung adenocarcinoma

Figure 1 Images of the patient on admission. A: An X-ray of the left femur showed an osteolytic change (arrow); B: Chest X-ray showed a tumor shadow; C: Chest computed tomography showed a 4-cm tumor, which was considered to be the primary lesion.

Figure 2 Histology of squamous cell carcinoma in the femur tumor. A: Single cell keratosis (arrows); tadpole cells (arrowhead; HE staining, × 40); B: Intercellular bridges (arrows; HE staining, × 40); C: Cytokeratin 5/6 immunostaining (× 4) (monoclonal mouse anti-human cytokeratin 5/6 antibody from clone D5/16 B4; DakoCytomation, Copenhagen, Denmark); D: p63 immunostaining (× 4) (Monoclonal mouse anti-human p63 antibody from Clone 4A4; Nichirei Biosciences Inc., Tokyo, Japan).

Figure 3 Histology of adenocarcinoma in the lung tumor. A: Glandular formations (arrows; HE staining × 40); B: D-periodic acid–Schiff suggests mucin production (arrows; × 40); C: Cytokeratin 5/6 immunostaining (× 4); D: p63 immunostaining (× 4).

Figure 4 Sequencing of epidermal growth factor receptor showing G719S in both the lung and femur samples. A: Tumor of the lung; B: Tumor of the femur. Nucleotides: Green; A: Black; G: Blue; C: Red.