Proximal Femoral Metastasis From Epidermal Growth Factor Receptor-Mutated Lung Adenocarcinoma Mimicking Osteosarcoma on Magnetic Resonance Imaging

Abstract

The aggressive nature of lung cancer is frequently accompanied by a high incidence of bone metastasis; however, proximal femoral metastasis from lung cancer is comparatively uncommon when compared to other malignancies. In this report, we present the case of a 53-year-old Asian male who presented with pain in the left thigh and back. Magnetic resonance imaging revealed severe bone destruction with involvement of adjacent soft tissue mass at the left thigh, exhibiting imaging findings that mimic osteosarcoma. Subsequent bone biopsy confirmed the diagnosis of epidermal growth factor receptor (EGFR)-mutated lung adenocarcinoma with bone metastasis. The patient achieved survival following administration of osimertinib and underwent surgery for femoral metastases without palliative surgery for lung cancer. Therefore, proximal femoral metastasis from EGFR-mutated lung adenocarcinoma should be considered as a differential diagnosis in patients suspected to have osteosarcoma. The imaging findings of proximal femoral metastasis from EGFR-mutated lung adenocarcinoma were presented, and their therapeutic management was discussed.

Keywords: EGFR mutation; Lung adenocarcinoma; Osteosarcoma; Proximal femoral metastasis.

Figure 1

(a-c) MRI scans indicating potential multiple metastatic lesions in bilateral proximal femur, ilium, ischium, pubis, and spine. (b) T1-weighted sagittal spin-echo sequence of the thigh and hip joint displaying a hypointense lesion in the left proximal femur. (c, d) T2-weighted sagittal spin-echo sequence with fat-suppression demonstrating a hyperintense lesion involving intraosseous and extraosseous soft tissue in the left proximal femur. MRI: magnetic resonance imaging.

Figure 2

(a) A neoplasm in the left upper lobe was observed on a computed tomography (CT) scan. (b) The presence of a neoplasm in the left lung was confirmed through an enhanced CT scan. (c) A follow-up CT scan at 3 months after osimertinib administration revealed shrinkage of the neoplasm in the left upper lobe.

Figure 3

(a) H&E staining (original magnification, × 400) depicting tumor cell morphology. Immunohistochemical analysis revealed expressions of CK7 ((b) original magnification, × 400) and TTF1 ((c) original magnification, × 400), confirming the diagnosis of lung adenocarcinoma. H&E: hematoxylin and eosin; CK7: cytokeratin 7; TTF1: thyroid transcription factor 1.