Mf. Meneses et al., BIZARRE PAROSTEAL OSTEOCHONDROMATOUS PROLIFERATION OF BONE (NORA LESION), The American journal of surgical pathology, 17(7), 1993, pp. 691-697
Bizarre parosteal osteochondromatous proliferation was first described
in 1983, when Nora et al. reported 35 examples of a proliferative les
ion involving the small bones of the hands and, less often, the feet.
No examples involving the large bones were reported. We present 65 cas
es of this condition, five from the Mayo Clinic files and 60 from our
consultation files, including 34 females and 31 males; patients' ages
ranged from 8 to 73 years (average, 33.9 years). Thirty-six lesions in
volved the hands, 10 the feet, 17 the long bones, one the skull, and o
ne an unknown site. The long bones involved were the radius (three les
ions), ulna (six), fibula (two), femur (three), tibia (two), and humer
us (one lesion). Roentgenograms typically showed a heavily calcific ma
ss attached to the underlying cortex and having a broad base. Histolog
ically, a large amount of hypercellular cartilage showed maturation to
trabecular bone, which frequently contained spindle cells in the inte
rtrabecular spaces, an. appearance that could lead to a mistaken diagn
osis of parosteal osteosarcoma. A helpful feature was the distinct blu
e tinctorial characteristic of the bone in the lesion. Follow-up infor
mation was available for 40 patients; approximately 55% had a recurren
ce. No metastasis had been reported in any of the 65 cases. Bizarre pa
rosteal osteochondromatous proliferations are a form of heterotopic os
sification and should not be mistaken for chondrosarcoma or osteosarco
ma.