Neuroendocrine carcinoma of the posterior mediastinum arising from a foregut cyst.

Neuroendocrine carcinoma of the posterior mediastinum is extremely rare. Described here is a patient with neuroendocrine carcinoma of the posterior mediastinum arising from a foregut cyst. A paravertebral mass detected in the posterior mediastinum of a 64-year-old man was spherical, solid and yellowish white. Some cystic or cleft-like spaces were present. Microscopically, the lesion was composed of proliferating round or polygonal tumor cells in a diffuse, solid or trabecular fashion with extensive necrosis and high mitotic activity. Components of glandular epithelia and smooth muscle layers were evident in the cystic wall. Immunohistochemically, the tumor cells were positive for both epithelial and neuroendocrine markers, including pan-cytokeratin, chromogranin A and synaptophysin. Neuroendocrine marker-positive cells were also present in the glandular epithelium of the cystic walls. It was considered that posterior mediastinal neuroendocrine carcinoma arose from a foregut cyst. Malignant change within a foregut cyst is very uncommon. This is the first report of a neuroendocrine carcinoma of the posterior mediastinum arising from a foregut cyst.