Malignant peripheral nerve sheath tumours (also called neurofibrosarcomas) are a rare, highly aggressive soft tissue sarcomas that arise from the peripheral nerves or cells associated with the nerve sheath, such as Schwann cells, peri-neural cells and fibroblasts. It is representing 10% of all soft tissue sarcomas in which it is considered as an extremely rare malignancy, especially in patients with neurofibromatosis type I. In the general population, it affects approximately 1 in 100,000 people. This article is reporting a 56-year-old Malay female patient who is a known case of neurofibromatosis type I for 20 years, presented with a lower back, pruritic, gradually increasing swelling during the last five months. Last month before the presentation, the lesion rapidly grows, reaching a size of (15×15 cm), accompanied by foul-smelling discharge and pain exacerbated with movement. Although no history of preceding trauma or accident, the mass bleeds within contact. In conclusion, only a few cases of giant malignant peripheral nerve sheath tumours reported in the literature describing its location and growth progression. We present a massive, extremely rapid growth of cutaneous exophytic malignant peripheral nerve sheath tumours over the lower back.