MPNST : Architecture
Malignant peripheral nerve sheath tumor (MPNST) is a highly cellular neoplasm resembling fibrosarcoma and is composed of monomorphic spindle cells arranged in interlacing fascicles, palisades, and whorls. The cells have comma-shaped, wavy or buckled hyperchromatic nuclei and indistinct pale cytoplasm. Some cases have plump oval or rounded nuclei. The tumor may show compact hypercellular areas alternating with hypocellular foci with myxoid stroma (as seen here). Focal nuclear palisading and whorled arrangement of spindle cells suggesting tactoid differentiation may also be seen. Other less commonly seen features include hyalinized cords and nodules and proliferation of plump epithelioid tumor cells within the vessel walls.