The anaplastic PXA, which occurs de novo or through recurrence, should be distinguished from glioblastoma by identifying the salient microscopic features of conventional PXA even in the anaplastic areas; and by demonstrating the expression of neuronal markers, in that the former is expected to have longer survival.

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An autopsy case of anaplastic ganglioglioma in the brain stem of a 12-year-old girl is reported. The ill-defined tumor involved the right cerebellar peduncle, medulla oblongata and upper cervical spinal cord, and showed mixed proliferation of many ganglioid cells and atypical pilocytic astrocytes with necrotic areas. Immunohistochemical studies revealed the presence of chromogranin A in most ganglioid cells and of metenkephalin in some large ganglioid cells. Glial cells were positive for glial fibrillary acidic protein and vimentin. Ultrastructurally, numerous dense-core granules of 90-220 nm in diameter were demonstrated in ganglioid cells and abundant glial filaments in glial cells. High neurosecretory activity in neuronal cells, suggested by chromogranin-immunoreactivity and dense-core granules, seems to be the most characteristic property of ganglion cell tumors.

While double pituitary adenomas have been found in approximately 1% of autopsy pituitaries, those in surgically resected material have been only rarely reported. We report herein 6 cases of double pituitary adenomas, which consisted of two histologically and/or immunohistochemically different areas among approximately 450 surgical specimens. Five out of 6 patients were men and the age was ranged between 18 and 61 years old. All these 6 patients presented acromegaly or acrogigantism and hyperprolactinemia was noted in 3 patients. In 2 patients (cases 1 and 2) the two adenomas belonged to different adenoma groups (GH-PRL-TSH group and FSH/LH group), while in the remaining 4 patients (cases 3-6) the two adenomas belonged to the same group (GH-PRL-TSH group). Thus, in all patients at least one of the two adenomas was GH-producing adenoma. Reasons for a high incidence of GH-producing adenomas in surgically resected double pituitary adenomas may include the presence of a variety of histologic subtypes among GH-producing adenomas and the advantage of cytokeratin immunostaining to distinguish these subtypes. In regard to pathogenesis of double pituitary adenomas, adenomas in cases 1 and 2 may be of multicentric occurrence, while those in cases 3-6 may occur through different clonal proliferation within originally one adenoma, resulting in diverse phenotypic expressions. Since there were patients with familial MEN 1 (case 2) and familial pituitary adenoma unrelated MEN 1 (case 3), genetic background should be also considered. Double pituitary adenomas in surgically resected material may not be so infrequent. Further molecular analysis will provide new insights into understanding the pathogenesis of pituitary adenomas and their mechanisms of multidirectional phenotypic diffrentiation.

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