The ligamentum flavum, of which there are only a few studies in the literature, has several features discussed in this work. On the macroscopic level, it has a metameric arrangement: it has two layers, superficial and deep, whose fibers are opposite, and it has close relations with the tendons of attachment of some spinal erector muscles. On the microscopic level, its structure is unique for a ligament, because of a predominance of elastic fibers, because of its intrinsic innervation at each level of the spine, and because this innervation grows poorer with increasing degeneration. The ligamentum flavum constitutes an active ligament, with an essential biomechanical role. Its injury is probably not without consequences, and therefore there are many technical problems about the surgical interlaminar approach.

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One hundred and ninety-two cases of supratentorial astrocytic tumors are classified in 4 groups according to the presence or absence in the pathological material of simple morphological criteria: abnormal cellular density, nuclear pleomorphism, neovascularization, necrosis. Each one of these criteria is strongly correlated with prognosis. Nevertheless only a simple classification in low and high grade lesions has a definite predictive value. A multivariate analysis utilizing Cox's hazard function confronts these histological findings with a number of clinical and etiological possible factors of prognosis. Age and performance status at the time of diagnosis are the best predictors of survival time. The clinical use of a predictive model derived from Cox's function analysis is discussed.

Recent progress in immunopathological studies of peripheral nerve and lymph node fragments together with 16 personal cases and numerous clinicopathological reports have suggested a new classification of peripheral neuropathies (PN) and lymphomas. These are: (1) PN due to local infiltrations by a T-cell lymphoma: (2) acute polyradiculoneuritis due to active demyelination and associated with infiltrates of a T-cell lymphoma in the epineurium, resembling Marek's disease (which is a T-cell lymphoma); (3) B-cell lymphoma proliferation which may be restricted to or predominate in the peripheral nervous system, with a large clinicopathological heterogeneity ranging from localized forms to ascending polyradiculoneuropathies; (4) angiotropic lymphoma, which is a B-cell lymphoma and may present as an acute mononeuropathy; (5) patients with acquired immunodeficiency syndrome due to lymphomatous infiltrates in the endoneurium, of which 2 cases of PN have been reported; (6) PN associated with organomegaly, endocrinopathy, M-component and skin lesions, certain cases being associated with a plasmocytoma and sometimes Castleman's disease but without any monoclonal gammopathy: (7) classic Guillain-Barré syndrome, prone to develop in patients with extraneural lymphoma but without any lymphomatous infiltrates in the peripheral nervous system; (8) certain cases (4 out of 16 in our series) where there is no clear relationship between PN and lymphoma, and there are mainly features of axonal degeneration. Inflammatory perivascular infiltrates were sometimes present in the epineurium.

An immunohistological study of 15 chordomas, six chondrosarcomas, four liposarcomas and seven carcinomas on paraffin embedded samples using anti-cytokeratin, anti-epithelial membrane antigen (EMA), anti-S100 protein, anti-vimentin and anti-neurofilaments showed that chordomas has a characteristic immuno-staining, i.e. positive for cytokeratin, EMA, S100 protein and vimentin; and negative for neurofilaments. This immuno-staining allows a clear distinction of chordomas from other tumours.