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A malignant peripheral nerve sheath tumor (MPNST) is a form of cancer of the connective tissue surrounding peripheral nerves. Given its origin and behavior it is classified as a sarcoma. About half the cases are diagnosed in people with neurofibromatosis; the lifetime risk for an MPNST in patients with neurofibromatosis type 1 is 8–13%. [2]
1% of nerve sheath and soft tissue neoplasms, respectively (>50 cases of intraneural perineuriomas and >300 cases of soft tissue perineuriomas have been described) Common presentation: focal, unilateral lesion affecting major peripheral nerves (sciatic, median, radial, brachial plexus) and their branches.
In perineural invasion, cancer cells proliferate around peripheral nerves and eventually invade them. Cancer cells migrate in response to different mediators released by autonomic and sensory fibers. Tumor cells secrete CCL2 and CSF-1 to accumulate endoneurial macrophages and, at the same time, release factors that stimulate perineural invasion.
The primary Schwann cell differentiation and neoplastic proliferations are characteristics of peripheral nerve sheath tumors. For instance, the Schwann cell, which is the major neoplastic cell component of neurofibroma, [7] is cytologically distinguished by the expression of S-100 protein and wavy nuclear outlines.
Malignant melanotic nerve sheath tumor (previously known as melanotic schwannoma) is a rare aggressive peripheral nerve sheath tumor that typically develops in conjunction with spinal or visceral autonomic nerves, consisting uniformly of Schwann cells displaying melanocytic differentiation.
A sarcoma is a malignant tumor, a type of cancer that arises from cells of mesenchymal (connective tissue) origin. [1] [2] Connective tissue is a broad term that includes bone, cartilage, muscle, fat, vascular, or other structural tissues, and sarcomas can arise in any of these types of tissues.
It is classified as a malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation. [citation needed] The unusual name "triton" was first used in reference to observation of supernumerary limbs containing bone and muscle growing on the backs of triton salamanders after the implantation of sciatic nerve tissue. [1]
The name "synovial sarcoma" was coined early in the 20th century, as some researchers thought that the microscopic similarity of some tumors to synovium, and its propensity to arise adjacent to joints, indicated a synovial origin; however, the actual cells from which the tumor develops are unknown and not necessarily synovial. [3]