Neurothekeoma (NT) sometimes extends to subcutaneous adipose tissue, skeletal muscle or epidermis, and thus may imitate some malignant situations. A 17-year-old female patient was admitted to another medical center with a swelling at her waistline. Plexiform fibrous histiocytoma was diagnosed, and she was referred to our clinic. Total re-excision was performed. The new pathology report indicated features of atypical NT. A case of atypical NT, which can be misdiagnosed as a malignant mesenchymal tumor, is discussed in this paper.