[42-year-old man with painless swelling of the ring finger].

A 42 years old man presented with a painless increasing swelling in the region of the proximal phalanx and metacarpal bone of the ring finger persistent since five months. Plain X-rays revealed increased soft tissue density. The possibilities of differential diagnostic of tumors in the region were discussed because essential for the correct procedure. Histology revealed a bizarre periostal osteochromatic proliferation (Nora lesion). This rare lesion must be distinguished from an periostic osteosarcoma.