Clear cell meningioma: report of a spinal case.

A sacrococcygeal case of clear cell meningioma in a 38-year-old man is reported. Compared to the seven spinal clear cell meningiomas described so far, this case demonstrated the highest recurrency rate. Multiple recurrences were most likely due to the extensive infiltrative growth pattern of the tumor hindering complete microscopic surgical resection. Histologic parameters were not relevant to predict recurrences, since cellular anaplasia was lacking and growth fraction was low in the first operation and all subsequent recurrences. In view of what is now known of clear cell meningiomas, the tumor showed all histologic and immunohistochemical features which are typical for this tumor entity. However, the tumor was first diagnosed by capable pathologists and neuropathologists as fibroma-like mesenchymal tumor, metastatic renal carcinoma, chordoma, chondroma untypical osteosarcoma, and microcystic meningioma. Correct diagnosis was made by electron microscopy which has revealed comparable findings to those of other rare electron microscopical cases reported so far; high content of cytoplasmic glycogen diffusely distributed throughout the cytoplasm or aggregated within vacuoles, intermediate filaments, desmosomes, interdigitation of cell membranes and large amounts of collagen fibers, some of which were of the giant amianthoid type. Since meningiomatous features of clear cell meningiomas are not obvious light microscopically and the tumors may be confused with nonmeningiomatous neoplasms, electron microscopical investigation is highly recommended in each case of suspected clear cell meningioma.