Spontaneous regression of a residual pineal tumor after resection of a cerebellar vermian germinoma

A case of multiple intracranial germ cell tumor in which a pineal tumor reg ressed spontaneously after resection df the cerebellar mass is reported. Im munohistochemical staining of the cerebellar mass showed that most of the i nfiltrating lymphocytes were positive for CD3 and CD8. The anti-Ki-67 monoc lonal antibody MIB-1 staining of the resected tumor revealed a high MIB-1 p ositivity ratio (36.1%) among the large tumor cells, and TUNEL staining dem onstrated that positivity in up to 6% of the tumor cells. Possible mechanis ms responsible for this spontaneous regression including immunological resp onses and apoptosis induced by T lymphocytes are discussed.