We experienced 7 cases of immunosuppressed patients with enhancing intracerebral lesions on CT and MRI at our hospital in the period between 2004 and 2008. The cases included 6 patients infected with HIV and 1 rheumatoid arthritis patient. Patients aged between 40 and 56, and they consisted of 6 males and 1 female. HIV patients are generally first treated for HIV associated benign diseases or infectious diseases, including Cryptococcus infections, fungal infections, and so on. When these treatments are not effective, a differential diagnosis for malignant lymphoma is required before considering radiation therapy and chemotherapy. We performed open biopsies on all cases, and used a computer aided navigation system to assist in our minimal invasive surgery. The average total volume of specimens attained by biopsy was about 1cm3 and enough to undertake an immunohistochemical study, a flow cytometric study, and a gene translication study of gamma immunoglobulin genes. The final diagnosis of the 7 cases were diffuse large B cell lymphoma, adult T cell lymphoma, toxoplasmosis, a lymphoproliferative state due to an EB virus infection, and immuno-reconstruction syndrome after treatments for HIV. Despite the fact that CT and MRI image studies were similar between patients, final diagnosis differed and included malignant diseases. In conclusion, we consider it difficult to make an accurate diagnosis of CT and MRI enhancing intracerebral lesions in immunosuppressed patients, and regard it as very important to undertake open biopsies to make a final diagnosis and to differentiate between a variety of disorders in such patients.

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Objective: In case of brain tumor resection it is important for neurosurgeons to know the boundary between the tumor and the normal apparatus, the cleavage plane. The objective of this study was to clarify the existence of the cleavage plane in the resection of the pituitary adenomas, intirinsic tumors. Methods: Inclusion criteria of this study were, 1） newly diagnosed cases, 2） Hardy's classification Grade 0, A, and B for suprasellar extension of the tumor, and 3） Knosp's Grade 0-4 for lateral extension of the tumor. From April in 2003 to April in 2008, 20 cases of pituitary adenomas were enrolled in this study. Results: All cases have the cleavage plane, so-called pseudocapsule. The thickness of the pseudocapsule was varied from 10 to 100μm. All sections examined showed that tumor cells were inside and within the pseudocapsule. Conclusion: Pituitary adenomas have the pseudocapsule which can be the cleavage plane in the surgical resection.

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Rare two cases of hemorrhagic PNET are reported. The first patient was one years old boy with the tumor located parietal lobe whose preliminary diagnosis was head trauma. Histological examination showed malignant and predominantly undifferentiated with evidence of focal attempts to differentiate along glial and neuronal lines. Cell culture showed glia differentiation .The second patient was an 73 years old woman whose tumor located in the fronttemporal lobe. She presented hemorrhage during radiotherapy followed tumor partial resection. Histologically,the hemorrhagic mechanism of PNET showing tumor necrosis and hemorrhagic infarction was suspected by vessel invasion, increasing of vascular permeability.

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