Telangiectatic osteosarcoma

Last revised by Joachim Feger on 23 Dec 2022

Telangiectatic osteosarcomas (TOS/TAEOS) are an uncommon variant of osteosarcoma 1-3

Telangiectatic osteosarcomas make up for 2-12% of high-grade osteosarcomas with varying frequencies between studies 1-6. They have similar demographics to that of conventional osteosarcoma and typically occur in adolescents and young adults 4,5 (reported age range of 3-67 years ref with a median age of 15- 20 years 5). There is a recognized male preference 4,5.

Telangiectatic osteosarcoma is considered a subtype of conventional osteosarcoma. Similarly, the diagnostic criteria are based on a combination of typical radiographic and pathological features.

Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 4:

  • imaging features of a bone tumor

  • osteoid matrix with neoplastic bone formation

  • permeative and destructive growth pattern

and in addition, the following criterion is required:

  • empty or blood-filled cystic spaces separated by septa

As with conventional osteosarcoma, the following histological criteria are desirable 4:

  • high-grade atypia of tumor cells

  • frequent atypical mitotic figures

Clinical and imaging-related characteristics indicating the diagnosis without the pathological information:

  • in adolescents (10-20 years)

  • bone tumor with osteoid matrix, cystic spaces with fluid-fluid levels, enhancing septae, permeative features and cortical destruction

  • location in a metaphyseal-diaphyseal region with epiphyseal extension

Telangiectatic osteosarcomas are a subtype of osteosarcoma characterized by empty or blood-filled cystic spaces separated by septa 1-6. A small telangiectatic component is present in most osteosarcomas, but to classify as telangiectatic osteosarcoma, the telangiectatic component should comprise >90% 7.

The most common sites are the metaphyses of long bones possibly with extension into the epiphysis or diaphysis especially around the knee (~60) 4-6:

  • distal femur: ~40-45%

  • proximal tibia: ~15-20%

  • proximal humerus: ~8-10%

  • proximal femur: ~7-8%

The femoral, humeral and tibial diaphyseal regions as well as the pelvic bones are less common with frequencies ranging from ~5-7% for the mid-femur to ~3% in the pelvis 5.

Rare locations are the fibula, skull and ribs with a frequency <2% each 5,8.

Grossly, telangiectatic osteosarcomas are characterized by the following features 1-5:

  • cystic, blood-filled spaces

  • multiple thin fibrous septa with sponge-like or honeycomb appearance

  • fish-flesh appearance of solid tumor portions

  • tumor size is 5-13 cm on average 3

Microscopically, telangiectatic osteosarcomas display a similar picture to an aneurysmal bone cyst with the following histological features 1-5:

  • hemorrhage and necrotic debris

  • blood pools without endothelial lining

  • septa of variable thickness

  • atypical stromal cells among osteoclast-like giant cells

  • atypical mitoses with moderate to high mitotic rate

  • nuclear hyperchromasia and pleomorphism

  • focal osteoid formation and sometimes lacelike osteoid matrix (maybe absent in biopsy sample) 4,5

Typically seen as an expansile lytic bone lesion at the metaphysis:

  • geographic bony destruction with a wide zone of transition tends to be more common than permeative bony destruction 9

  • less osteoid matrix than the conventional type

  • pathological fractures are frequent

  • low attenuating fluid-fluid levels within the lesion (in ~80% of cases)

  • useful at assessing associated cortical destruction

  • thick peripheral and nodular septal enhancement

  • osteoid matrix mineralization

  • commonly shows fluid-fluid levels within the lesion (~90% of cases) with variable signal intensity

  • allows appreciation of surrounding soft tissue components

  • signal characteristics are often heterogeneous

  • enhancement of septa with nodularity as well as the soft tissue component may be observed 10

  • hemorrhage appears as hyperintense on T1 and variable signal intensity on T2

Overall, lesions tend to show marked but heterogeneous uptake on bone scans. May demonstrate a region of central photopenia representing a doughnut sign 9,10.

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

  • form and location

  • blood-filled or empty cystic spaces, fluid-fluid levels

  • thickened fibrous septa, nodular/solid components

  • tumor margins and transition zone

  • cortical striations indicating prominent intraosseous veins

  • cortical destruction

  • soft tissue extension

  • pathological fractures

The treatment of telangiectatic osteosarcoma is often similar to that of conventional osteosarcoma: chemotherapy followed by wide surgical resection and limb salvage or amputation. 

The survival rate of telangiectatic osteosarcoma (estimated at ~70%) is similar to that of conventional osteosarcoma.

They are associated with a high rate of pathological fractures 6,11 and fracture risk is higher than conventional osteosarcoma 6.

Telangiectatic osteosarcoma was first described by the English surgeon Sir James Paget (1814-1899) in 1854 as a ‘medullary cancer of bone with excessive vessels and blood cysts’ 13. Later in 1903, the entity has been called ‘malignant bone aneurism’ by the American surgeon Gaylord 14 before the American pathologist James Ewing designated it as an osteosarcoma variant in 1922 and 1939 15.

Considerations on plain film include 5:

  • aneurysmal bone cyst (ABC): should not have any soft tissue component outside the lesion and will have a narrower transitional zone. Smooth septal and rim enhancement is seen without nodularity, osteoid matrix mineralization or aggressive features like cortical destruction and infiltration into surrounding tissue (unlike telangiectatic osteosarcoma) 11

  • giant cell tumor of bone: no soft tissue component

  • osteolytic metastatic bone lesions: should not have any fluid levels

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