Pagetoid involvement of bronchioles by metastatic breast carcinoma

We report a case of a 36-year-old female with endobronchiolar spread of breast carcinoma in the lung. The patient had recently been diagnosed with invasive ductal breast carcinoma and imaging of the lungs revealed bilateral lung nodules. She then underwent a wedge resection of a lung nodule. The biopsy revealed a subpleural metastatic nodule of invasive ductal carcinoma with an intra-alveolar pattern of spread at its advancing edge. Several smaller foci of intra-alveolar tumor were noted as well as pagetoid spread of tumor cells along a 0.9 mm wide bronchiole. The neoplastic cells were TTF-1 negative, GATA3 positive and ER positive. This is the third reported case of pagetoid spread of metastatic breast carcinoma along the bronchial tree. This case emphasizes the importance of examining not only bronchi but also bronchioles to detect this unusual pattern of spread of metastatic breast carcinoma in lung resection specimens.