Neurofibroma and neurofibrosarcoma are an infiltrative benign peripheral nerve sheath tumor, classified as a differentiated form of Schwannomas which can affect both the peripheral and central nerve tissue.
Although schwannomas are entirely formed of neoplastic Schwann cells, neurofibromas are a mixture of Schwann cells, perineurial cells and fibroblasts, with the Schwann cell the primary neoplastic cell.
A collective term 'benign peripheral nerve cell tumor' has been advocated instead of schwannoma or neurofibroma due to the close histological appearance of these two tumor types as well as both benign schwannomas and benign neurofibromas behave similarly in clinical setting.
Clinically affected dogs usually present with a slow-growing tumor, often affecting nerve-rich tissues such as the ovaries, .
Blood tests and imaging studies (radiographs, ultrasonography and MRI) are usually unrewarding.
Diagnosis is based on presenting clinical history and needle biopsy or surgical biopsy during mass excision.
Neurofibromas are usually single, well-demarcated, expansile tumors, but a plexiform variant has been reported that is composed of multiple nodular masses.
Histological examination of neurofibromas usually reveals three common forms; localized, diffuse and plexiform types. Macroscopically, these tumors are frequently composed of well demarcated multinodular masses with centrally located nerve fiber bundles surrounded by neoplastic nerve sheath tissue. Microscopically, these tumors can appear as classic, cellular, collagenous, myxoid, and pigmented forms, with slender, elongated cells containing buckled and/or wavy nuclei in a fibromyxoid stroma with thin, wire-like collagen fibers. Within the mass, nerve fibers can be identified.
Immunohistochemistry usually reveals positive staining limited to neoplastic Schwann cells.
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