CASE REPORT: Extralobar pulmonary sequestration presenting a paravertebral mass with extensive fibroadenomatous change in an adult

We report herein an unusual case of pulmonary extralobar sequestration (ELS) showing fibroadenomatous change. It was incidentally found in a 41-year-old woman presenting with a paravertebral mass on chest radiography during a routine health check-up. Computed tomography reveled a 3.6 cm, well-defined solid mass in the paravertebral region. The resected mass was predominantly solid and well-covered by pleura with irregular cystic spaces. Microscopically, it showed a unique fibroadenomatous change, dilated bronchiolar structures and prominent fibrous stroma. In the periphery of the mass, a small portion of the lung with normal alveolar structure was noted. The lining epithelium showed reactivity for thyroid transcription factor-1 by immunohistochemical staining.