Primary Pulmonary Mucinous Adenocarcinoma in a Patient with Previous Ovarian Mucinous Adenocarcinoma: A Diagnostic Challenge

Background/Aim: Primary ovarian mucinous adenocarcinoma and pulmonary mucinous adenocarcinoma are distinct entities; however, their overlapping histopathological and immunohistochemical features may create significant diagnostic challenges, particularly in distinguishing primary tumors from metastatic disease. This case report aims to highlight the diagnostic challenge of distinguishing primary pulmonary mucinous adenocarcinoma from metastatic ovarian mucinous adenocarcinoma and to emphasize the importance of integrating clinical, histopathological, and immunohistochemical findings in the differential diagnosis.
Case: A 49-year-old female patient presented with pain. Her medical history revealed that she underwent fertility-sparing surgery and debulking for a right ovarian mass in 2001, followed by chemotherapy and successful pregnancy via in vitro fertilization. Molecular analysis was negative for EGFR, ROS1, and BRAF mutations. The patient had a history of living in Kahramanmaraş for over 20 years, and environmental exposure included possible dye exposure related to her spouse’s occupation. In 2017, lesions were detected in the right upper and lower lobes of the lung. Histopathological examination revealed mucinous adenocarcinoma in both lobes. Immunohistochemically, tumor cells were CK7 and CA125 positive, focally CK20 positive, and negative for TTF-1, Napsin-A, CDX2, PAX8, ER, PR, and p16. The presence of “mucinous adenocarcinoma in situ” areas in both lesions supported the diagnosis of two separate primary lung tumors rather than metastatic disease. Additionally, anthracosis and emphysematous changes were observed in the surrounding lung parenchyma.
Conclusion: Distinguishing between primary and metastatic mucinous tumors requires a comprehensive evaluation of clinical, radiological, histopathological, and immunohistochemical findings. This case highlights the diagnostic complexity of mucinous tumors and underscores the importance of a multidisciplinary approach in accurate tumor classification and management.

Keywords: Ovarian mucinous adenocarcinoma, Pulmonary mucinous adenocarcinoma, Differential diagnosis, Immunohistochemistry