Telangiectatic osteosarcoma

Telangiectatic osteosarcomas (TOS) are an uncommon variant of osteosarcoma that represent 2.5-12% of all osteosarcomas. 

Epidemiology

TOS have similar demographics to that of conventional osteosarcoma and typically presents in adolescents and young adults (reported age range of 3-67 years with a mean age of 20 years). There is a recognised male predilection.

Pathology

Most osteosarcomas have a small telangiectatic component but in order to classify as a telangiectatic osteosarcoma the telangiectatic component should comprise >90% ¹.

Macroscopic appearance

Most of the tumour comprises of large blood filled spaces separated by thin bony septations.

Histology

Microscopically the tumour consist of vascular sinusoids surrounded by thin septaesepta, osteoid matrix and cells with significant pleomorphism and high mitotic rate.

Associations

A telangiectatic osteosarcoma can be a secondary lesion (arising in association with fibrous dysplasia, Paget disease, or post radiation therapy).

Location 

Most common locations by site are: 

• around knee:
  • femur: 50-62%
  • tibia: 10-25%
• humerus: 12-16%

In terms of location within bone:

• metaphyseal: ~80%
• diaphyseal: ~20% 

Radiographic features

Plain radiograph

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

• geographic bony destruction with wide zone of transition tends to be more common than permeative bony destruction ⁶
• less osteoid matrix than conventional type
• pathological fractures are frequent

CT

• 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 mineralisation

MRI

• 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 septationssepta as well as the soft tissue component may be observed
• haemorrhage appears as hyperintense on T1 and variable signal intensity on T2

Nuclear medicine

Overall, lesions tends to show marked but heterogeneous uptake on bone scans. May demonstrate a region of central photopenia representing a doughnut sign ^3,6.

Treatment and prognosis

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

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

Complications

They are associated with a high rate of pathological fractures ⁴.

Differential diagnosis

Considerations on plain film include:

• aneurysmal bone cyst (ABC): should not have any soft tissue component outside the lesion
• giant cell tumour of bone: again no soft tissue component 
• osteolytic metastatic bone lesions: should not have any fluid levels

History and etymology

First described by J Paget in 1854 ⁷.