Metastatic Lung Adenocarcinoma to the Uterus Mimicking a Primary Uterine Malignancy: A Case Report

ABSTRACT Background Lung adenocarcinoma is the most prevalent subtype of non‐small cell lung cancer and exhibits a high tendency for distant metastasis. However, uterine metastasis with synchronous multiorgan involvement is extremely rare and prone to misdiagnosis due to atypical clinical presentations. To date, fewer than 20 cases of lung adenocarcinoma metastasizing to the uterus have been documented globally, most of which present with typical gynecological symptoms, making our atypical case highly educational and complementary to existing clinical data. Case Herein, we describe a 77‐year‐old postmenopausal female patient who initially presented with lumbago and dizziness without typical pulmonary or gynecological symptoms, with an ECOG performance status of 1. Imaging studies raised suspicion of a primary uterine malignancy, but pathological biopsy, immunohistochemistry, and genomic testing ultimately confirmed advanced lung adenocarcinoma with multiorgan metastases (uterus, lung, liver, bone). Molecular analysis identified an EGFR exon 21 p.L858R mutation, and the patient received palliative local radiotherapy combined with osimertinib targeted therapy. During treatment, the patient developed mild radiation‐induced fatigue and slight myelosuppression, which were fully relieved after symptomatic supportive care, with no severe unexpected adverse events observed. Conclusion This case illustrates the atypical metastatic pattern of lung adenocarcinoma, underscores the pivotal role of pathological and immunohistochemical examinations in differentiating primary from metastatic tumors, and offers a reference for managing diagnostically challenging cases. Early and accurate diagnosis coupled with genomic‐guided personalized therapy is critical for enhancing quality of life and prognosis in patients with advanced lung cancer.