Amyloidosis is a heterogeneous group of protein deposition diseases with more than 40 known clinical presentations. Localized amyloidosis occurs when the protein deposits exist in a singular location. Patients with diabetes mellitus who inject insulin at the same site can develop localized insulin-derived amyloidosis (AIns) at the injection site, which can be confused clinically with lipoma, lipohyperplasia, lipoatrophy, and fat necrosis. Histologic examination is performed to confirm localized AIns. We report a case of a patient with a long history of type 2 diabetes who presented with a subcutaneous mass in the abdomen at a preferred insulin injection site. Examination by light microscopy revealed diffuse deposition of eosinophilic material. Two of the tissue fragments contained numerous 30-40 μm spherical bodies within the eosinophilic material. The bodies had dark centers with peripheral eosinophilic material. Polarized sections stained with Congo red showed apple green birefringence, a characteristic of amyloid. Immunohistochemistry was positive for insulin antibodies in the dark spherules and the surrounding matrix. Proteomic analysis by mass spectrometry showed that the Congo red-positive material was insulin. Electron microscopy showed a background matrix consisting of nonbranching protein fibrils measuring 8.8-16.1 nm, consistent with amyloid; the spherules contained dark globular proteins in the center surrounded by nonbranching fibrillary proteins. Because these spherules were positive for insulin by immunohistochemistry and showed amyloid ultrastructurally, we refer to them as amyloid insulin bodies. The identification of AIns, specifically with amyloid insulin bodies, is important for diagnosis and treatment and may further our understanding of amyloidogenesis.

This case of a unilateral isolated mass with neither local nor systemic involvement adds to the ever-enlarging spectrum of IgG4-ROD presentations.

Objective and Importance: Ganglioglioneurocytoma is not yet a well defined clinical and histopathological entity; recent reports outline the histopathological features of this very rare trimorphous tumor, under different names with its basic components of gangliocytoma, neurocytoma and glioma. Four previous reports described this tumor in eleven patients. This is the first case report describing ganglioglioneurocytoma in the posterior fossa. Clinical Presentation and Intervention: A 31-year old male with midline posterior fossa ganglioglioneurocytoma is described, providing the neuroimages and histopathological studies. Conclusion: Ganglioglioneurocytoma is a rare mixed neuronal and glial tumor that can also occur in the posterior fossa. Can. J. Neurol. Sci. 1999; 26: 207-210 Mixed cell tumors in the CNS containing both glial and neuronal elements are rare. Gangliogliomas account for about 1 % of all brain neoplasms, which usually present with seizures in children. They have been reported in all levels of the neuroaxis, but were more common in the temporal lobe. The tumor contains a glial component usually astrocytic of variable cellularity and a ganglionic component of large often binucleated neurons scattered or in clusters that immunostain with synaptophysin and chromogranin. These tumors usually have a good prognosis following surgical resection.' Central neurocytomas are rare tumors of the CNS, classically affect young adults, and arise in the lateral ventricles near the foramen of Monro. However, they have been reported away from the ventricles, 2 in the cerebellum 3 and in the spinal cord. 4 The tumor consists of neurocytes; small round cells with perinuclear halo formation and stain with synaptophysin. Under the electron microscope, neurosecretory granules in the perinuclear cytoplasm and neurites are characteristic. This neoplasm is usually curable with total resection whenever possible. Glioneurocytomas are another mixed tumor with glial and neurocytic components. They have been reported with similar clinical and pathological findings. 6 Since then, a total of eleven cases were reported describing tumors with such a morphology, usually associated with glial component of well differentiated astrocytes. In this paper we describe the 12th case, which to our knowledge is the first to be reported arising in the posterior fossa. CASE REPORTA 25-year-old previously healthy male presented with a one year history of progressive headache and blurring of vision. Physical exam showed papilledema and ataxic gait but normal cranial nerve function. CT scan images revealed a midline posterior fossa mass at the level of the fourth ventricle with a large dorsal cystic component and a smaller solid ventral component with calcification. The solid mass partially enhanced with IV contrast. It seemed to originate from the cerebellum and compressed the fourth ventricle causing obstructive hydrocephalus (Figure 1). The patient underwent surgery for gross total resection and had an uneventful recovery. Postoperativ...

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