Epidermal growth factor receptor-mutated lung adenocarcinoma diagnosed from endometrial polyp metastasis: A case report and literature review.

Endometrial metastasis from the lung primary remains is rare. Moreover, the literature only contains case reports of endometrial metastasis from the primary lung cancer. An 83-year-old female patient presented with postmenopausal uterine bleeding and anemia. Endometrial thickening was detected using transvaginal ultrasound and endometrial curettage was performed. Histopathology revealed adenocarcinoma infiltration on an endometrial polyp surface. On histologic examination, high-grade serous carcinoma and clear cell carcinoma diagnoses were initially considered. The tumor cells were immunohistochemically negative for Wilms' tumor 1 and wild-type for p53 expression; however, it was positive for Napsin A. Primary lung adenocarcinoma (LUAD) metastasis was also included in the differential diagnosis. Thyroid transcription factor 1 was positive, whereas paired box gene 8 (Pax8) was negative in tumor cells. Primary LUAD metastasis was diagnosed since a lung mass was radiologically confirmed. Furthermore, epidermal growth factor receptor-exon 19 mutation was detected by molecular analysis. In addition to the clinical and morphological features, this case report emphasizes the importance of multiple immunohistochemical panel applications for the correct diagnosis.