The specimen is the lower end of a femur almost completely surrounded by a nodular tumour some
10.0 cm in maximum diameter. The growth is predominantly extraperiostial but there is some
invasion of bone apparent towards the lower end. On the posterior surface there is evidence of
invasion of muscle.
This woman presented at the age of 36 with a two-year history of ache in the left knee at
the end of the day. A lump was present; arteriograms showed a vascular pattern consistent with
malignancy. Biopsies were taken and it was concluded that the tumour was a parosteal osteoma.
Because of the uncertain nature of the tumour which some authorities regarded as malignant, and
because of the abnormal vascular pattern an amputation was carried out. The patient is alive 28
years later. Further histological examination of the lesion shows areas which are undoubtedly a
low-grade osteogenic sarcoma. (Weston, Reid, and Saunders 1958, Journal of Bone & Joint
Surgery 40B, 722).