Endobronchial metastatic breast cancer with pagetoid histology mimicking bronchial pagetoid squamous cell carcinoma in situ

We report a case of a 56-year-old woman with endobronchial breast cancer metastasis of unusual histology. The patient presented with persistent cough, and a lesion was noted in the left mainstem bronchus on bronchoscopic examination. Biopsy revealed extensive squamous metaplasia of bronchial epithelium along with large, atypical cells exhibiting pagetoid intraepithelial spread within squamous mucosa. Immunohistochemical stains were compatible with a diagnosis of metastatic breast adenocarcinoma with pagetoid spread. To our knowledge, this is the first reported case of endobronchial breast cancer metastasis with this histologic presentation. In this report, we describe the clinical, radiographic, bronchoscopic, histologic, and immunohistochemical characteristics of this case. We provide a brief review of existing literature on endobronchial breast cancer metastasis. In addition, we discuss the principal differential diagnosis of bronchial pagetoid lesions. This report raises awareness of this uncommon manifestation of metastatic breast cancer.