Bone Tumors and Tumor-like Conditions of Bone

Matthew V. Cronin, MD; Tudor H. Hughes, MBBS, MD, FRCR

Disclosures

Appl Radiol. 2012;41(10):6-15. 

In This Article

Malignant Bone Lesions

Osteosarcoma

In patients <30 years, osteosarcoma and Ewing's sarcoma are the most common primary malignant tumors of bone. Osteosarcoma can be subdivided into medullary, parosteal, periosteal and telangiectatic, all of which carry different prognoses and treatment options.

Medullary osteosarcoma (Figure 7) is the most common, occurring in adolescents and young adults typically between the ages of 15 and 25 yrs. These are rapidly growing, heterogeneous, metaphyseal lesions that show cortical destruction, aggressive periostitis, and a wide ZOT. Osseous matrix formation is the norm and a soft tissue component is often present. Evaluation with MRI shows variable T1 and T2 signal characteristics secondary to varying degrees of ossification. High T2 signal is often seen around the periphery of the lesion, presumably related to adjacent edema. Metastatic skip lesions are commonly seen and should be worked up with radionuclide evaluation.

Parosteal osteosarcoma (Figure 12) originates from the parosteal soft tissues and is less aggressive than the medullary form. This lesion typically occurs in older patients. Growth is circumferential around the involved bone and typically does not initially result in cortical destruction. As such the prognosis for this lesion is more favorable. However, if intramedullary extension does occur, the prognosis is more guarded.

Figure 12.

Parosteal osteosarcoma. (A) Frontal and (B) lateral radiographs of the distal femur in a 16-year-old male demonstrate florid new bone formation projecting medially, laterally, and posteriorly.

Telangiectatic osteosarcoma (Figure 9) has the potential to be misdiagnosed as a giant cell tumor or chondroblastoma, as it is characteristically lytic and deceivingly nonaggressive in appearance. Subtle cortical erosion or periostitis may be present. Periosteal osteosarcomas are rarer than those mentioned previously. Periosteal osteosarcoma is a surface lesion that typically produces a sunburst or Codman's triangle periostitis. Adjacent cortical erosion is usually seen.[3,4,7]

Ewing's Sarcoma

Ewing's sarcoma is the most prevalent primary malignancy of bone in children and is second to osteosarcoma in adolescents and young adults. Classically, Ewing's is described as a diaphyseal-based, permeative lesion with a wide ZOT and aggressive periostitis (Figure 13). An associated soft tissue mass is invariably present. It should be noted, however, that Ewing's is not limited to a diaphyseal location; in fact , it is often found in metaphyseal or metadiaphyseal locations. This lesion typically affects the appendicular skeleton in children but is found more axially in adolescents. The radiographic appearance of Ewing's is nonspecific and can overlap that seen with infection or eosinophilic granuloma. MRI characteristics show low signal on T1, high signal on T2, and typically an adjacent soft-tissue mass that may be heterogeneous in appearance secondary to focal necrosis.[3,4,7]

Figure 13.

Ewing's sarcoma. (A) Frontal and (B) lateral radiographs, (C) sagittal T1 and (D) coronal T2 with fat saturation MRI of the left humerus in a 15-year-old girl with arm pain and a mass. There is a permeative mixed lytic and sclerotic lesion involving the distal humeral shaft with accompanying periosteal reaction. The MRI shows a nonspecific low T1, high T2-signal pattern and soft-tissue involvement.

Chondrosarcoma

Chondrosarcoma is typically a low-grade malignant osseous tumor found in adults. The radiographic appearance can be misleading, as often few aggressive features are present. This is a lytic, metaphyseal-based lesion, which may have a "snowflake" chondroid matrix. However, completely lytic lesions are not unusual (Figure 14). Cortical erosion, soft-tissue extension, and pain may or may not be present. Low-grade chondrosarcoma can be difficult, if not impossible, to differentiate from an enchondroma, which is the primary alternative consideration in the differential diagnosis. On MRI, low grade, differentiated chondrosarcomas will appear bright on T2 imaging, with more homogeneous signal than that of higher-grade lesions.[3,4]

Figure 14.

Chondrosarcoma. (A) Frontal radiograph, (B) axial CT, (C) sagittal-T2 and (D) sagittal-T1, fat-saturated, post-gadolinium MRI of a 34-year-old man with a sacral chondrosarcoma. There is a large necrotic tumor with enhancing margins surrounding the central rings-and-arcs pattern of calcified matrix arising from the sacrum.

Undifferentiated Pleomorphic Sarcoma (Malignant Fibrous Histiocytoma) and Fibrosarcoma

Although these two lesions have differing histologic appearances, they are indistinguishable radiographically. These are relatively rare bone tumors that may arise de novo or secondary to an underlying osseous lesion, such as Paget's disease, fibrous dysplasia, or nonossifying fibroma, or at sites of prior radiation. This lesion has a permeative appearance with an indistinct ZOT and may or may not have an associated soft tissue component (Figure 15). The MRI appearance is again nonspecific, with low T1 signal and heterogeneously bright signal on T2-weighted images.[3,7]

Figure 15.

Undifferentiated Pleomorphic Sarcoma (Osseous malignant fibrous histiocytoma). AP radiograph in a 59-year-old man with a basicervical pathologic fracture through an ill-defined lytic lesion. These lesions tend to have an aggressive permeative pattern.

Metastatic Disease and Myeloma

Osseous metastatic lesions have multiple appearances and therefore are often included in the differential for atypically appearing sclerotic or lytic lesions. Several metastatic lesions, such as renal cell, thyroid, melanoma, and choriocarcinoma, are classically lytic in appearance. However, other than renal cell cancer, this need not always be the case. Metastatic prostate cancer (Figure 16) will typically show sclerotic lesions, but breast, lung (Figure 17) and gastrointestinal malignancies can also mimic this appearance. As is the case with other lesions, MRI is useful for evaluation of soft tissue extent and staging; however, biopsy is needed for diagnosis.[3–5]

Figure 16.

Metastatic disease. AP radiograph of the proximal femur in an elderly man. Although the classic pattern of metastatic disease is either moth-eaten lytic lesions or relatively well-defined sclerotic lesions, occasionally a very aggressive pattern such as this may be seen. In this case the primary is prostatic carcinoma. With this appearance the prostatic primary is often hormone insensitive.

Figure 17.

Non-small cell lung cancer metastasis. (A) Frontal and (B) frog leg radiographs of a 66-year-old man. For a lesion to be this obvious on the frog leg view, it must involve the cortex. For this reason it is referred to as a cookie bite lesion. Cortical metastases most often are adenocarcinoma and come from the lung.

Multiple myeloma is a diffuse, permeative malignancy found in adults over the age of 35 to 40 yrs. While this lesion is typically lytic, a rare form of sclerotic myeloma is seen in association with POEMS syndrome (Polyneuropathy, Organomegally, Endocrinopathy, Monoclonal gammopathy and Skin changes). In the early stages, myeloma may be preceded by a predominantly lytic plasmacytoma that is usually found in the axial skeleton. Multiple myeloma ultimately ensues, typically with a diffuse axial and appendicular distribution. Multiple "punched out" lesions in the calvarium and axial skeleton are a classic appearance of this disease (Figure 6). Patients inevitably suffer from renal failure secondary to Bence-Jones protein deposition or associated amyloidosis. Of note, radionuclide studies with Tc99m-MDP are ineffective in demonstrating myelomatous lesions.[3,4]

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