Abstract
Objective : Differential diagnosis among primary lung adenocarcinoma, malignant mesothelioma and breast cancer metastasis is difficult in cases of malignant pleural effusion. We discussed the morphological and immunohistochemical pitfalls in the differential diagnosis among these conditions based on pleural fluid cytology.
Study Design : At first, we report the case of a 62-year-old woman who had undergone resection for breast cancer 28 years ago and presented with malignant pleural effusion. Additionally, immunohistochemical analysis was conducted on 16 invasive lobular and 24 invasive ductal carcinoma cases of the breast.
Results : The cytological findings of pleural effusion were consistent with a diagnosis of malignant mesothelioma. Immunohistochemically, the tumor cells in the pleural fluid cytology specimen were positive for cytokeratin 7, EMA, calretinin, CEA and estrogen receptor, and negative for cytokeratin 20, MOC-31, cytokeratin 5, D2-40, WT-1, CD146, progesterone receptor, HER2, GCDFP-15, TTF-1 and napsin A. Based on the histological and immunohistochemical findings of a pleural biopsy specimen, we finally concluded that the tumor was a breast lobular carcinoma recurrence. Additional immunohistochemical revealed that three of 16 (19%) invasive lobular carcinomas (ILC) and 12 of 24 (50%) invasive ductal carcinomas (IDC) of the breast were positive for MOC-31, and three of 16 ILC (19%) and two of 24 IDC (8%) were positive for calretinin.
Conclusion : It is important to be aware that there are morphological and immunohistochemical pitfalls in the differential diagnosis among primary lung adenocarcinoma, malignant mesothelioma and breast cancer metastasis based on pleural fluid cytology.
