Periosteal osteosarcoma

Last revised by Mohd Ashyiraff Ilani Bin Ismail on 3 Nov 2023

Periosteal osteosarcomas are intermediate-grade bone-forming neoplasms originating on the bony surface in strong association, typically underneath the periosteum.

Periosteal osteosarcomas are the second most common type of surface-based osteosarcoma after parosteal osteosarcoma and account for 1-2% of all osteosarcomas 1-4. Periosteal osteosarcomas are seen in a wide age range from the first to the seventh decade with a peak in the second decade of life 1.

The diagnosis of periosteal osteosarcomas is based on a combination of typical radiographic features and histology.

Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:

  • imaging features of a bone tumor

  • histology of an intermediate-grade mostly chondroblastic osteosarcoma

  • origin from the surface of the bone under the periosteum

  • typically involves the diaphysis of long tubular bones

Typical symptoms include swelling and/or pain lasting for weeks to months 1.

Periosteal osteosarcomas are predominanty chondroblastic osteosarcomas with a chodroid matrix. They typically arise from the inner cambium layer of the periosteum 4 and are attached to the underlying cortex 1. The cytologic grade is intermediate which is higher than parosteal osteosarcoma and lower than conventional osteosarcomas 1.

The etiology of periosteal osteosarcomas is unknown.

Periosteal osteosarcomas tend to be diaphyseal  and are found in the following locations 1-5:

  • the femur and tibia are the most common sites

  • occasionally in other long bones and/or flat bones

  • rarely in the hand and feet or the craniofacial bones

Grossly tumors are characterized by the following features 1,5:

  • ovoid broad-based lobulated pale cartilaginous appearance

  • attachment to the osseous cortex in continuity with the inner periosteum

  • possible reactive bony spiculae

  • commonly delineated capsule

Microscopically, periosteal osteosarcomas are characterized by cartilaginous areas with a transition to an osteoid matrix with the following histological features 1,5:

  • lobules of atypical cartilage

  • intervening bands of reactive bone

  • periosteal reaction with linear reactive bone spicules separated by cartilaginous matrix

  • primitive undifferentiated mesenchymal cells at the tumor perimeter with mitoses and nuclear atypia

On immunohistochemistry stains periosteal osteosarcomas express SATB2 which is not particularly helpful in the differentiation from periosteal chondrosarcoma 1.

Typical imaging characteristics include 3,4,6:

  • broad-based cortically attached tumor with a partially mineralized soft tissue mass

  • extrinsic erosion of thickened underlying diaphyseal cortex with a surface-base crater

  • perpendicular or spiculated periosteal reaction

  • usually involves ~50% of the cortical circumference

  • intramedullary extension is rare

  • lucent fusiform mass attached to the bony surface

  • variable mineralization

  • cortical thickening with ectosteal scalloping or “saucerization” 6

  • solid, lamellated or spiculated periosteal reaction and occasionally Codman triangle 1

Periosteal osteosarcomas feature a chondroid matrix that is characterized by a low attenuation on CT images 1,4,6.

 As on the other imaging modalities on MRI periosteal osteosarcomas appear as cortical-based tumors with strands of ossification within the lesion perpendicular radiating from the surface and more pronounced towards the cortex 1,3,4. They usually surround about half of the affected bone 3. Compared to muscle lesions are usually hyperintense in T2 and intermediated-weighted images 6 with areas of low-signal intensity due to matrix mineralization. They might have reactive abnormal intramedullary signal changes, even though true bone marrow infiltration is rare 1,4.

  • T1: intermediate to high signal

  • T2: intermediate to high signal

  • STIR/IMFS: heterogeneously high signal

  • T1 C+ (Gd): enhancement

The radiological report should include a description of the following 4:

  • form, location and size

  • tumor margins and transition zone

  • circumferential extent

  • periosteal reaction

  • cortical erosion, cortical breakthrough

  • medullary involvement (less likely)

  • infiltration of neurovascular structures (if present)

Periosteal osteosarcoma is of intermediate grade with the prognosis being better than conventional osteosarcoma, but not as good as parosteal osteosarcoma (which is usually low grade) with 5-year and 10-year survival rates of 89 and 77-86% 1,8. Bone marrow invovement is rare but if present is associated with less favorable outcome 1. Treatment usually consists in wide excision. Chemotherapy does not seem to influence prognosis or survival and has been associated with the occurance of secondary malignancies in occasional cases 9. Local recurrences, metatsases and death usually occur within a period of 3 years after the diagnosis 1,8.

Periosteal osteosarcomas were first recognized by the American pathologist James Stephen Ewing in 1939 and again described later by the American pathologist Louis Lichtenstein 9,10 .

Differential diagnoses that look similar to periosteal osteosarcoma on imaging studies include the following entities 4:

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