telangiectatic osteosarcoma

Definition: A malignant bone-forming tumour characterized by large spaces filled with blood with or without septa. The roentgenogram typically shows a purely lytic destructive process without matrix mineralisation. Telangiectatic osteosarcoma should be considered a variant of osteosarcoma.

Images

 Telangiectatic osteosarcoma

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Epidemiology

 As an uncommon variant of osteosarcoma, telangiectatic osteosarcoma accounts for 0.4-12% of all osteosarcomas.

 Telangiectatic osteosarcoma occurs in a male-to-female ratio of 2:1. Although disease can be found in patients aged 3-71 years, it rarely occurs in persons older than 25 years. Most patients present when they are aged 10-20 years.

Clinical synopsis

Telangiectatic osteosarcoma appears as a painful, radiographically lytic mass lesion in the metaphyseal portion of the long bones.

The clinical presentation of telangiectatic osteosarcoma closely resembles that of conventional osteosarcoma. However, local pain, soft-tissue masses, and fractures are the most common presenting symptoms and signs.

Site of lesions

 Telangiectatic osteosarcoma lesions are usually osseous, but extraosseous lesions have been reported.

 In the long bones, these tumors usually occur in the metaphyseal region within the medullary cavity. As the tumors expand and destroy the cortex, blowout fractures may occur. These lesions may also occur in a diaphyseal location.

 The distribution pattern of telangiectatic osteosarcomas in the long bones is as follows12 :

• Distal femur - 48%;
• Proximal humerus - 12%;
• Proximal tibia - 10%;
• Proximal femur - 8%;
• Fibula - 5%;
• Midfemur - 2%;
• Midhumerus - 2%

These tumors also occur in the mandible.

Telangiectatic osteosarcoma also has been noted to arise in extraosseous soft tissues in the forearm, thigh, and popliteal fossa.

Predisposition

Potentially, telangiectatic osteosarcomas can arise in bones involved with Paget disease, where it can mimic other forms of conventional osteosarcoma.

Telangiectatic osteosarcomatous differentiation has been reported in parosteal osteosarcoma, in dedifferentiated chondrosarcoma arising in the background of osteochondroma, in association with aneurysmal bone cysts, and in osteitis deformans.

Although rare, telangiectatic osteosarcomatous differentiation has been seen in cases of malignant phyllodes tumor of the breast and in cases of ovarian sarcoma.

Fine-needle aspiration biopsy

The examination of samples obtained at fine-needle aspiration biopsy reveals sheets of highly polymorphous cells. The cells include spindled cells reminiscent of fibroblasts, as well as round or oval malignant cells. Multinucleated cells also are frequently identified. Nuclear hyperchromasia, nuclear membrane irregularity, and prominent nucleoli are noted in the malignant cells. Increased mitotic activity may be noted as well. The cytoplasm is variable and granular.

Core-needle or conventional biopsy permits a definitive diagnosis of telangiectatic osteosarcoma.

Macroscopy

The tumors, which may be 10-20 cm in diameter, have the appearance of a hemorrhagic mass. An aneurysmal bone cyst is often suspected. Sometimes, these lesions have multicystic channels filled with blood that correspond to the radiographic appearance of fluid-filled spaces. A solid, fleshy, sarcomalike appearance is not appreciated in these lesions.

Microscopy

 large blood lakes seen at a low magnification reminiscent of findings in an aneurysmal bone cyst
 lining of blood-filled lakes shows overt malignant cells
 atypical mitosis with tripolar mitosis
 numerous giant cells (can mimic a giant cell–rich osteosarcoma)

Telangiectatic osteosarcoma is characterized by dilated, blood-filled vascular spaces lined by malignant osteoblasts. These osteoblasts are separated by fibrous septa, which contain the malignant cells, multinucleated giant cells, and tumor osteoid.

Malignant cells are noted in a background of blood and necrotic debris. Because the pleomorphic hyperchromatic malignant cells may be diluted in the necrotic and hemorrhagic background, a careful examination to recognize these elements is imperative.

Blood lakes, rather than endothelium-lined spaces, are present.

In some cases, an osteoid matrix may not be visualized except within the septal walls, which may be thin and difficult to find. In such cases, a characteristic radiographic appearance, when correlated with a careful microscopic search for features suggestive of malignancy, helps in the correct interpretation of the findings.

In some cases, low-power examination reveals a morphologic pattern that is reminiscent of an aneurysmal bone cyst.

Differential diagnosis

 aneurysmal bone cyst
 conventional osteoblastic osteosarcoma

A potential trap is created by a radiologic impression of an aneurysmal bone cyst and the characteristic gross features of that cyst. However, examination of the cyst lining reveals overt malignant cells, often with increased mitotic activity, as seen in the first image below. These cells may lie adjacent to the benign osteoclastic giant cells.

In some cases, these giant cells are numerous, and the tumor mimics a giant, cell–rich osteosarcoma, as seen in the second image below.

Unlike an aneurysmal bone cyst, telangiectatic osteosarcoma has an osteoid matrix that is delicate and lacelike in appearance. Also, the stroma between the dilated vascular spaces often contains malignant cells.

Radiology

On conventional radiographs, pure lytic lesions define telangiectatic osteosarcomas.

The tumor margins are frequently permeative. However, well-defined margins have been noted. A sclerotic rim suggests another diagnosis.

The lytic lesions may have fluid-filled spaces.

Cortical destruction and infiltration into the surrounding soft tissues can occur.

This tumor may also evoke a periosteal bone reaction, and it can be associated with the Codman triangle. A pattern of parallel striations is highly suggestive of telangiectatic osteosarcoma.

 The radiological differential diagnosis of telangiectatic osteosarcoma, based on imaging studies, often includes the following:

• aneurysmal bone cyst
• Ewing sarcoma
• Langerhans cell histiocytosis
• fibrosarcoma of bones
• malignant fibrous histiocytoma of bones

Etiology

Telangiectatic osteosarcomas are presumed to originate from transformed osteoblasts or from stem cells that are of mesenchymal derivation.

Results from transmission electron microscopic examination show that, in addition to undifferentiated osteoblastlike and fibroblastlike tumor cells, angiosarcomatous elements may be observed in this malignant bone tumor.

Endothelial, cell-like structures, including pinocytotic vesicles, tight intercellular junctions, fine fibrils, and Weibel-Palade bodies, are seen in the cytoplasm of these cells.

Such observations suggest that telangiectatic osteosarcoma may be derived from multipotential mesenchymal cells, with possible differentiation along various pathways.

Familial occurrence has been reported at least once.

Links

 emedicine.medscape.com

See also

 osteosarcomas