R. BAZ, C. NISCOVEANU
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tion of bizarre (even spindle shaped) fibroblast in the
intertrabecular spaces of disorganized bone has been re-
ported. Typically the cartilage lobules show mild atypia
and moderate mitotic activity is seen in the spindle cells.
This often conf uses the diagnosis and the lesion n eeds to
be distinguished from conventional osteosarcoma, low-
grade parosteal osteosarcoma, and chondrosarcoma. There
is no “columnation” of the cartilage as in osteochon-
droma, rather the cartilage is disorganized and irregular,
with patc hy areas of ossification [7].
The recommended treatment of choice is excising the
pseudocapsule over the lesion, any periosteal tissue be-
neath the lesion, and decorticating any abnormal appear-
ing areas in the underlying host bone, as this procedure
has less recurrence rate than simple excision of th e lesion
[8].
These lesions have a remarkable tendency to recur:
recurrence rates between 29% and 55% in a 2-year in-
terval have been reported, and almost half of those pa-
tients have had a second recurrence. [9] Nora and col-
leagues presented 35 cases of BPOP with 18 (51%) local
recurrences [1]. Meneses and colleagues reported a re-
currence rate of 55% in a series of 65 patients [2] and
Dhondt and colleagues reported a recurrence rate of 29%
in 24 patients [10]. However, despite a high tendency to
recur and a sometimes atypical histological appearance,
no malignant transformation, metastases, deaths or asso-
ciated systemic diseases have been described so far in
patients with BPOP.
4. Conclusion
Nora’s lesion represents a distinct radio-pathological
entity. It should be considered whenever the diagnosis of
osteochondroma is made. Being a rare lesion, the diag-
nosis of Nora’s lesion is challenging for most radiolo-
gists and pathologists as illustrated by this case and oth-
ers. The particularity of our case is the distinct localiza-
tion of the lesions, with very few cases of BPOP of the
skull bein g r ep or t ed.
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