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The authors describe the computed tomography (CT) and magnetic resonance (MR) imaging findings of a 69-year-old woman and a 69-year-old man with a nonfunctional mediastinal parathyroid cyst. In the described cases, unenhanced CT showed homogeneous areas of water density, and unenhanced MRI showed homogeneous areas that were isointense to cerebrospinal fluid, reflecting their serous fluid contents. Both cysts were located posterior to the left lower pole of the thyroid gland with an extension to the superior mediastinum, either anterior or posterior to the left brachiocephalic vein. CT and MR imaging findings of parathyroid cysts are nonspecific, and they are often difficult to differentiate from other cystic lesions located in the lower neck or in the superior mediastinum. However, a parathyroid cyst should be considered when radiologic images demonstrate its characteristic location, posterior to the thyroid gland, with an extension to the superior mediastinum.

The case of an eight-year old male with a pineal tumor is reported, in which metastases occurred to extraneural organs. The pineal tumor consisted of portions of benign teratoma, malignant ependymoma and embryonal carcinoma. Only the embryonal carcinoma metastasized. The intracanial and spinal subarachnoid space alos was invaded by disseminated embryonal carcinoma. There have been seven other similar cases reported. All patients were males from five to 34 years of age.

Carcinogenicity of an aqueous extract of bracken was studied in inbred strain ACI rats. In Experiment 1, Group 1 rats received a diet containing unprocessed dry bracken powder for 3 months, Group 2 received the boiling water extract of dry bracken as drinking water for 16 months, Group 3 received the cold water extract of dry bracken as drinking water for 16 months, and Group 4 received a diet containing the concentrated boiling water extract of dry bracken during the whole experimental period. Rats in Experiment 2 also received a diet containing the boiling water extract of dry bracken. A control group was fed a normal diet. Majority of the animals in Group 1 developed multiple ileal tumors, such as adenomas and adenocarcinomas. In Group 2, 6 of 11 rats which survived beyond 7 months developed tumors in either the ileum or urinary bladder, or in both. Rats in Group 3 had no tumor. In Group 4 and in Experiment 2, all the animals except 1 rat in Experiment 2 had urinary bladder tumor. Furthermore, almost all the rats in these groups had simultaneously ileal tumors. Based on these results, it may be assumed that the carcinogen in bracken is extractable in boiling water and is most probably also water-soluble.