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Pacheco et al. J Cancer Metastasis Treat 2020;6:49 I http://dx.doi.org/10.20517/2394-4722.2020.85 Page 11 of 15

Pathogenesis
[2]
No consistent genetic abnormality has been reported for periosteal osteosarcoma .

Diagnostic ancillary techniques
Compared to low-grade central osteosarcoma and parosteal osteosarcomas, MDM2 and CDK4 are very
rarely expressed in periosteal osteosarcoma and therefore they do not seem to be molecules central to the
[47]
control of cancer development, growth, and progression in this rare subtype of osteosarcoma .
Main differential diagnosis
BPOP arising in long bones may be mistaken for a periosteal osteosarcoma, due to its rapid growth, high
rate of local recurrences and atypical histology [38,39] . BPOP does not exhibit the brisk mitotic activity nor the
level of cytological atypia observed in periosteal osteosarcomas. In addition, blue bone is a feature of BPOP
absent in periosteal osteosarcoma.

Parosteal osteosarcoma arises in metaphysis of long bones in slightly older population. Their radiological
growth patterns are dissimilar. Microscopically their recognition is usually straightforward due to the fact
that parosteal osteosarcoma is predominantly fibroblastic, is typically low-grade, and contains abundant
tumor bone; whereas periosteal osteosarcoma is predominantly chondroblastic and of intermediate to high
grade.

Differentiating a periosteal osteosarcoma from a high-grade surface osteosarcoma is of prognostic and
therapeutic importance, as high-grade surface osteosarcoma behaves in a much more aggressive manner.
High-grade surface osteosarcomas most frequently arise in metaphysis of long bones of extremities.
Histologically, periosteal osteosarcoma shows less anaplasia and more prominent chondroid differentiation
than high-grade surface osteosarcoma. High-grade surface osteosarcoma is a high-grade tumor (grades 3
[2]
or 4), whereas periosteal osteosarcoma is an intermediate grade tumor (grades 2 or 3) .
Periosteal chondrosarcoma arises predominantly in metaphyseal locations and in older patients. The
neoplastic cartilage lacks marked nuclear pleomorphism, mitotic figures are rare, and osteoid or bone
formed by the neoplastic chondrocytes are absent.

Treatment and prognosis
Treatment consists of en bloc resection with wide margins without chemotherapy. Periosteal osteosarcoma
has less aggressive behavior compared to high-grade osteosarcoma, including a lower propensity for
systemic recurrence which is reported to be around 15% in periosteal osteosarcoma [21,48] . The 10-year
overall survival rate is 77.1%-84% [44-46] .

High-grade surface osteosarcoma
Definition and clinical features
High-grade surface osteosarcoma is a high-grade, malignant, bone-forming neoplasm arising in the
bony surface with minimal or no involvement of the underlying cortical bone. It is the least common
type of surface osteosarcoma, representing approximately 1% of all osteosarcoma types. It mostly affects
adolescents and young adults with a peak incidence in the second decade of life and a striking male
[1]
predominance . The skeletal distribution is similar to that of conventional osteosarcoma, most frequently
involving the metaphysis of the distal femur, proximal tibia, and proximal humerus.

Imaging
[1]
X-rays show mixed non-mineralized and mineralized matrix with fine cloud-like areas of opacity .
Periosteal reaction is uncommon, and the margins are indistinct [Figure 5]. Up to one third of the tumors