Spontaneous regression of a malignant primary bone tumour.

A histologically confirmed malignant, primary bone tumour in the pelvis, presumably an osteosarcoma, underwent spontaneous regression. The large tumour was inoperable and gave rise to severe pain as well as difficulty in walking. After 2 years of progression, with increasing destruction of the pelvic bones, the clinical and radiological condition improved spontaneously, and at present the patient is alive, almost symptom-free, after 6 years follow-up.