[A case of pineal teratoma with interesting radiological findings].

A rare case of mature pineal teratoma with interesting radiological findings in a 16-month-old infant is reported. The patient was referred to our clinic because of generalized convulsions. A CT scan showed marked hydrocephalus and a low density mass lesion without contrast enhancement in the pineal region. A CT cisternography demonstrated the lesion as a filling defect area on the image produced immediately after the emergent V-P shunt, and a filling area 24 hours later. The lesion was of signal intensity on T-1 weighted MR image and of high signal intensity on T-2 weighted MR image, equal to CSF intensity. These radiological findings were compatible with an arachnoid cyst in the quadrigeminal cistern, so we performed the excision of both anterior and posterior cyst walls using the occipital tentorial approach. However, the histology of the cyst wall was not compatible with that of an arachnoid cyst, showing neuroepithelial-like cell lining with positive staining for cytokeratine. The postoperative follow-up on MRI was continued for 31 months. An MRI performed 9 days after the first operation showed, compared with the gray matter, iso-signal intensity area and high signal intensity area on T-1 weighted image. At first, we thought this was because of bleeding of the pineal gland brought on by the operative maneuver. However, the mixed intensity lesion shown on T-1 weighted images gradually expanded and distorted, and finally showed the typical MR images for a teratoma. The operative findings using the occipital transtentorial approach were typical for a teratoma.(ABSTRACT TRUNCATED AT 250 WORDS)