Solitary fibrous tumor of the meninges occurring after irradiation of a mixed germ cell tumor of the pineal gland.

Twenty-nine months after surgery, irradiation, and systemic chemotherapy for a pineal mixed germ cell tumor, an 11-year-old Caucasian male developed a 3 cm dural based nodule in the occipital lobe that proved to be a solitary fibrous tumor by immunohistochemical and ultrastructural examination. Differential diagnosis included fibrous meningioma, neurofibroma, Schwannoma, cranial fasciitis of infancy, and solitary fibrous tumor. A Masson trichrome stain revealed a prominent collagenous stroma and reticulin staining exhibited strong pericellular positivity. Immunohistochemical staining demonstrated diffuse vimentin and focal CD34 positivity of tumor cells. Ultrastructural examination revealed fibroblastic differentiation. These features are consistent with solitary fibrous tumor. Although we favor a radiation-induced origin for the neoplasm, alternative explanations for the tumor's origin include cerebrospinal fluid spread from the original germ cell tumor or a de novo neoplasm.