Motor disorder in "normal pressure" hydrocephalus.

was pain free and walking well on a pylon before receiving a definite prosthesis. Examination of the amputation specimen (Fig. 1) showed an illdefined red tumour lying deep to the Achilles tendon, tumour nodules mingling with adjacent adipose tissue. A number of separate tumour masses were also present in both superficial and deep fascia, the most proximal being attached to the tibia 12 cm above the lateral malleous. Histological examination of the tumour showed regular polyhedral cells grouped around blood vessels (Fig. 2). There was evidence of tumour infiltration in many areas and an occasional suggestion of vascular invasion. Mitoses were very infrequent. Special stains showed mast cells in considerable numbers in and around the tumour. Comparison of this tumour with known examples of compact glomus tumours left little doubt that this was a glomus tumour but displaying histological evidence of malignancy.