Giant malignant peripheral nerve sheath tumor of the scalp.

Herein, we describe a rare case of giant malignant peripheral nerve sheath tumor of the head in a 38-year-old Japanese man. The tumor measured 210 mm at its largest diameter and was ulcerated, hemorrhagic, multilocular and non-mobile. It should be noted that the patient stubbornly refused to see a doctor for a long time, resulting in the extreme growth of the tumor. We suspect a psychological basis for this behavior. Dermatohistopathological findings of the biopsy indicated ancient schwannoma and total excision was therefore performed. However, after 4 months, the patient developed multiple metastases and died. Post-mortem skin biopsy revealed features of malignant peripheral nerve sheath tumor. We performed immunohistochemical studies on the primary and recurrent lesions and concluded that there was a difference in the expression of Ki67 and p16. We propose that the expressions of Ki67 and p16 should be checked for all lesions of peripheral nerve sheath tumor for distinguishing benign from malignant forms.