Intraneural angiosarcoma and angiosarcoma arising in benign and malignant peripheral nerve sheath tumours: clinicopathological and immunohistochemical analysis of four cases
Angiosarcomatous differentiation represents the least common form of heterologous differentiation in malignant peripheral nerve sheath tumours (MPNST), and is seen most frequently in patients with neurofibromatosis type 1. More rarely, it has been reported in patients without stigmata of neurofibromatosis, or in benign nerve sheath tumours and peripheral nerves. This study was undertaken to confirm this rare association. Four cases of angiosarcoma arising in a peripheral nerve, in a long-standing schwannoma and in two MPNST are described. Immunohistochemical studies were performed on paraffin sections with the alkaline phosphatase-antialkaline phosphatase method. An intraneural high-grade epithelioid angiosarcoma arose in the left posterior tibial nerve of a 78-year-old man, a well to moderately differentiated angiosarcoma was seen in an ancient schwannoma of the lateral neck in a 73-year-old women, and an angiosarcoma of varying grades of differentiation developed in a recurrent MPNST in the thigh of 38-year-old man. In addition a high-grade MPNST in the axillary region of a 30-year-old man showed foci of heterologous high-grade angiosarcomatous differentiation. The neural and endothelial lines of differentiation were confirmed in each case by positive immunohistochemical staining for neural and endothelial markers, respectively. In all cases tested, the neural differentiated cells stained immunohistochemically positive for antibodies against vascular endothelial growth factor. This study confirms the rare association of angiosarcoma arising in peripheral nerves, as well as in benign and malignant peripheral nerve sheath tumours.