Giant-cell tumour of the tendon sheath.

An unusual case of giant-cell tumours of the tendon sheath (syn. Pigmented villonodular tenosynovitis or fibrous xanthoma) of a long thumb flexor is presented. The unusual features are: two distinctly different tumours of almost similar size and shape arising from the tendon sheath at its either ends but with a segment of normal tendon sheath in between and presence of early malignant changes in the distal tumour with a benign proximal one, confirmed microscopically. Lastly, radiograph showed definite bony involvement in the proximal phalanx of the thumb. On extensive review of the literature, I found reports of rare presentation of malignant changes and bony erosion, but none had these various features.