Congenital mediastinal bronchogenic cyst with malignant transformation: an autopsy report

A rare autopsy case of mediastinal bronchogenic cyst with malignant transformation is presented. The cyst had been located in the anterior mediastinum for at least 28 years in a 52 year old male. Chest X-ray findings showing rapid enlargement of the cyst and biopsy of the spine for lumbago made a clinical diagnosis as suspicious mediastinal cystic teratoma with malignant transformation metastasizing to the spine. Postmortem examination revealed that the cyst was located in the anterior mediastinum extending to the left pulmonary hilum and had no connection with the tracheobronchial tree. The cyst wall consisted of bronchus-like tissue including ciliated epithelium, hyaline cartilage, smooth muscle and mucoserous glands. There were no teratomatous components in the wall. Malignant tumor predominantly consisting of round cells occurred in the thickened cyst wall and grew into the cyst cavity with direct invasion of the lung and metastases to the liver, adrenal glands, bone marrow of the lumbar spine and lymph nodes. An immunohistochemical study showed that the tumor cells frequently expressed cytokeratin, epithelial membrane antigen and carcino-embryonic antigen, occasionally CA19-9, vimentin and neuron-specific enolase. From these findings, the tumor was diagnosed as undifferentiated carcinoma arising in the mediastinal bronchogenic cyst.