Low-grade malignant soft-tissue perineurioma: interphase fluorescence in situ hybridization

Perineuriomas are usually benign soft-tissue tumors that arise from perineurial cells of the peripheral nerve sheath. Low-grade malignant perineurioma is a rare type of perineurioma, presenting with infiltrative growth, low mitotic activity, and a lack of necrosis. This report describes a case of low-grade malignant perineurioma in a 60-year-old man who presented with a growing tumor on the dorsal side of his left wrist. The tumor was surgically excised and showed no adhesion to the surrounding muscle and no continuity with nerves. There was no evidence of recurrence or metastases 12 months after surgery. Histology indicated that the tumor contained hypercellular and hypocellular areas with spindle-shaped cells proliferating in storiform patterns or perivascular whorling. There was moderate infiltrative growth into the surrounding tissue. There was an evident central infarction but no coagulative necrosis. Mitotic figures were observed at 5/10 high-power fields. On immunohistochemistry tumor cells were found to be positive for epithelial membrane antigen, glucose transporter protein 1, and claudin-1. Approximately 18.4% of tumor nuclei were labelled for Ki-67. Interphase fluorescence in situ hybridization on paraffin sections indicated a loss of chromosome 13. This suggests that chromosome 13 abnormalities could also be involved in perineurioma with low-grade malignant potential.     

Bilateral intraneural perineurioma presenting as ulnar neuropathy at the elbow

We describe a 36-year-old woman with progressive bilateral ulnar neuropathy. Sonographic and magnetic resonance imaging studies revealed extensive focal ulnar nerve enlargement at the elbow. Histological studies gave evidence of an intraneural perineurioma. Because intraneural perineurioma usually appears as a single mass lesion at sites other than typical entrapment sites, this mode of presentation is unusual. We discuss the nature of this benign tumor and the differential diagnosis of nerve enlargement. Knowledge of possible causes of nerve thickening is crucial when performing imaging in patients with neuropathies.     

Perineurial Cell Differentiation in Benign Tumors and Tumorlike Proliferation of Peripheral Nerves

An unusual, benign, spindle cell peripheral nerve sheath tumor (PNST) is reported that on ultra-structural examination was composed only of perineurial cells. The neoplastic cells showed positive immunoreactivity for S-100 protein and negative immunoreactivity for epithelial membrane antigen; this is not the expected immunophenotype of a perineurioma. Continued examination of benign PNSTs using electron microscopy and immunohistochemistry has the potential to reveal additional variations in the cellular composition and immunophenotype of these soft tissue tumors. PNSTs such as the one described will renew the debate about the cytogenesis of the perineurial cell and its role in PNSTs.     

A case of intraneural perineurioma presenting with monomelic atrophy in a child

We report the case of an 11-year-old girl who developed slowly progressive atrophy of the left lower extremity. She suffered from mild dilated cardiomyopathy of unknown cause since 4 years of age. When she was 7 years old, her family noticed that her left extremity was thinner compared to the right one. Computed tomography showed atrophy and areas of low density in the left gluteus maximus, thigh, and calf muscles. The left sciatic nerve showed gadolinium enhancement on magnetic resonance imaging. A biopsy of the left sural nerve revealed pseudo-onion bulbs. Immunohistochemical staining was positive for epithelial membrane antigen and negative for S100 protein. Electron microscopy demonstrated myelinated or unmyelinated nerve fibers surrounded by concentric layers of perineurial cells. These results indicated intraneural perineurioma. The tumor was estimated at least from the nerve root to the ankle joint. The length of nerve involvement in this patient was the highest recorded in the literatures. Intraneural perineurioma is a very rare disorder, but is tend to be found in youth. This disorder should be considered when we see children with monomelic weakness and/or atrophy.     

Plexiform Soft Tissue Tumor Composed Predominantly of Perineurial Fibroblasts (Perineurioma)

A 15-year-old girl presented with a small, indolent mass near the knee joint. Light microscopy revealed a peculiar myxoid plexiform tumor composed of cytologically bland cells. Interpretation of the initial biopsy material was controversial. Subsequent immunohistochemical studies revealed tumor cells to be strongly reactive for epithelial membrane antigen (EMA) and negative for S-100 protein. Ultrastructural studies revealed tumor cells with long, thin, bipolar cell processes and discontinuous basal laminae. They had no epithelial or histiocytoid features. Admixed among the tumor cells were Schwann cells, but they represented a rare and scattered component of the overall cell population. These features are most consistent with a so-called perineurioma and contrast with those of plexiform neurofibroma and traumatic neuroma (two lesions strongly positive for S-100 protein and showing a distinctive EMA immunoreactivity pattern with focal peripheral staining of neural bundles).