Classification

Benign tumors are classified as latent, active, or aggressive. A latent benign tumor (stage 1) is intracapsular, is usually asymptomatic, and never metastasizes. An active benign tumor (stage 2) is also intracapsular and rarely metastasizes but is actively growing and often symptomatic. An aggressive benign tumor (stage 3) often breaks through its capsule and extends into an adjacent compartment. Rarely do these tumors metastasize. Oliveira and co-workers have provided an overview of the principles and problems of histologic grading of tumors.

Enneking has classified sarcomas of bone and soft tissue into various stages according to their histologic grade, the location of the tumor relative to anatomic compartments, and the presence of metastases. A low-grade tumor has well-differentiated cells, few mitotic figures, few or no atypical cells, little necrosis, and no vascular invasion. High-grade tumors have frequent mitoses; are poorly differentiated; have atypical cells, necrosis, and little matrix; and show vascular invasion.

The ability to treat malignant tumors successfully with limb salvage depends on understanding sarcoma behavior. As stated by Enneking, “A sarcoma grows centrifugally like a spreading ripple on a pond. However, as it expands it follows the path of least resistance.” If a tumor remains within its compartment, either osseous or fascial, it can be removed successfully by resecting the entire compartment. A bone is considered to be a compartment, as is a muscle or a joint. Tumors may invade adjacent compartments and become extracompartmental. The Enneking staging system is shown in Table 28-1 .

As tumors grow, they compress surrounding tissues into structures that resemble fibrous capsules. This surrounding tissue contains tumor cells, known as satellites. In addition, there may be tumor cells in surrounding normal tissue, called skips. Within a bone there may also be skip metastases, with intramedullary tumor extending well proximal to the apparent extent of the primary tumor.

Clinical Features

The clinical manifestations in a patient with a musculoskeletal tumor are often a useful clue to the diagnosis. A child with a pathologic fracture and no previous symptoms most often has a benign lesion of bone that has gradually weakened the cortex and resulted in a fatigue fracture through a cystic lesion. In contrast, a gradually enlarging mass accompanied by increasing pain, especially at night, suggests a diagnosis of primary malignancy. Soft tissue tumors are most often painless and come to a medical provider’s attention because the patient or parent notices a mass. The more aggressive the tumor, the shorter and more alarming the period of onset.

The presence of a palpable mass is an important finding on physical examination. The examiner should determine its size, consistency, and mobility and whether it is painful on palpation. A rapidly growing lesion is more likely to be malignant than benign. In taking the history, it is helpful to compare the size of the mass with a dime, nickel, quarter, or half-dollar, or, if the tumor is larger, with a tennis ball, football, and so on. It is important to measure and record the size of the tumor as accurately as possible for comparison and subsequent examinations.

The consistency of the mass is determined next. Is it firm or soft? Does it feel cystic or bony and hard? A cystic or fluid-filled mass should be examined with a flashlight to determine whether it transilluminates. In general, fluid-filled masses are commonly benign, whereas large, hard masses are more likely to be malignant. Is there a distinct change from normal to abnormal at the margins of the mass? Does the mass have the same consistency as the surrounding normal tissue? Malignant swellings usually invade adjacent tissues. An increase in local temperature is more suggestive of a malignant than a benign lesion.

Mobility of a mass is of great help in ascertaining its nature. When the mass is fixed, it is either attached to bone or intraosseous. An osseous tumor is unaffected by muscle contraction. Intramuscular tumors are usually mobile when the muscle is relaxed and become fixed when the muscle contracts. Deep, mobile lesions that are extramuscular are beneath the deep fascia and extramuscular. Tumors that are superficial and can be moved have not invaded deep fascia and are probably benign.

Tenderness on palpation indicates an active process and is a result of an inflammatory response. An abscess or infection is very painful and is usually accompanied by other signs of inflammation, such as erythema, edema, lymphangitis, and adenopathy, whereas moderate tenderness is indicative of an active neoplastic process, and the absence of tenderness suggests a quiescent lesion. One should, however, be wary because rapid growth and necrosis of a malignant tumor may mimic infection. This may be a problem, for example, in distinguishing between Ewing sarcoma and osteomyelitis. When a rapidly growing malignant tumor is subcutaneous, it may cause vascular dilation, increased local heat, and skin turgor; such a tumor may be mistaken for thrombophlebitis or an infectious process. A firmer feeling and lack of local pitting edema, as well as the cutaneous tissue being not as red as in infection, however, characterize a neoplastic inflammatory response. Point tenderness is indicative of lesions such as osteoid osteoma or a neural or glomus tumor.

Joint range of motion may be limited because of muscle spasm or mechanical interference. There may be reactive synovitis when the lesion is adjacent to a joint or if the joint is directly involved. Muscle atrophy is not uncommon, and an antalgic limp may be present.

A vascular tumor is suspected if elevation or steady, firm pressure causes a diminution in its size; if the size is increased by the use of a venous tourniquet; or if a thrill or palpable pulsation is present. A pathologic fracture may occur in primary or metastatic malignant tumors, or one may complicate a benign process such as a unicameral bone cyst.

Invasion of a nerve will cause neurologic symptoms and signs, such as stabbing pain, paresthesia, hypoesthesia, or motor weakness. Pathologically, the nerve may be encased by the lesion or trapped against bone or rigid fascia. Neurologic dysfunction is uncommon except when tumors are in anatomic areas where nerves are unable to move freely, such as the sciatic notch or neural foramina.

Radiographic Findings

Anatomic Site of the Lesion

The location of a bony lesion is an important diagnostic clue ( Box 28-1 ). Epiphyseal lucent lesions are usually a chondroblastoma, infection, or occasionally an eosinophilic granuloma. Epiphyseal lesions after growth plate closure are generally giant cell tumors. The metaphysis is a common site for benign tumors, unicameral cysts, osteoid osteomas, and osteosarcomas. Diaphyseal lesions include fibrous dysplasia, Ewing sarcoma, and adamantinoma.

Box 28-1

Common Anatomic Sites of Primary Bone Tumors

Spine

Posterior Elements (Spinous Process, Lamina, Pedicles)

• 
  

  Aneurysmal bone cyst

  
  
• 
  

  Osteoma

  
  
• 
  

  Osteoblastoma

Anterior Elements (Vertebral Body)

• 
  

  In a child

  
  
  
  
  • 
    

    Histiocytosis X (“vertebra plana”)

    
    
  • 
    

    Hemangioma

  
  
  
  
• 
  

  In an adult

  
  
  
  
  • 
    

    Metastases

    
    
  • 
    

    Multiple myeloma

    
    
  • 
    

    Paget disease

    
    
  • 
    

    Hemangioma

    
    
  • 
    

    Chordoma

  
  

Long Bones (Physes Open)

Epiphysis

• 
  

  Chondroblastoma

  
  
• 
  

  Eosinophilic granuloma (epiphyseal osteomyelitis)*

Metaphysis

• 
  

  Multiple benign lesions such as a unicameral bone cyst

  
  
• 
  

  Common site for osteogenic sarcoma

Diaphysis

• 
  

  Fibrous dysplasia

  
  
• 
  

  Histiocytosis X

  
  
• 
  

  Ewing sarcoma

  
  
• 
  

  Osteoblastoma

  
  
• 
  

  Adamantinoma

  
  
• 
  

  Lymphoma

Parosteal

• 
  

  Myositis ossificans *

  
  

  * Not a tumor.

  
  
  
  
• 
  

  Osteosarcoma

  
  
• 
  

  Chondrosarcoma

  
  
• 
  

  Enchondroma

Ribs

• 
  

  In children and adolescents

  
  
  
  
  • 
    

    Fibrous dysplasia

    
    
  • 
    

    Ewing sarcoma

    
    
  • 
    

    Metastases

  
  
  
  
• 
  

  In adults

  
  
  
  
  • 
    

    Ewing sarcoma

    
    
  • 
    

    Chondrosarcoma

    
    
  • 
    

    Fibrous dysplasia

    
    
  • 
    

    Multiple myeloma

    
    
  • 
    

    Metastases

  
  

Pelvis

• 
  

  In children

  
  
  
  
  • 
    

    Ewing sarcoma

    
    
  • 
    

    Fibrous dysplasia

    
    
  • 
    

    Aneurysmal bone cyst

    
    
  • 
    

    Osteoblastoma

  
  
  
  
• 
  

  In adults

  
  
  
  
  • 
    

    Ewing sarcoma

    
    
  • 
    

    Chondrosarcoma

    
    
  • 
    

    Paget disease

    
    
  • 
    

    Multiple myeloma

    
    
  • 
    

    Metastases

  
  

Scapula

• 
  

  Ewing sarcoma

  
  
• 
  

  Osteoblastoma

  
  
• 
  

  Aneurysmal bone cyst

Multiple Lesions

• 
  

  In children

  
  
  
  
  • 
    

    Multiple hereditary exostoses

    
    
  • 
    

    Fibrous dysplasia (Albright syndrome)

    
    
  • 
    

    Histiocytosis X

    
    
  • 
    

    Enchondroma (Ollier disease)

    
    
  • 
    

    Multiple hemangiomatosis

    
    
  • 
    

    Metastases—neuroblastoma, hypernephroma

    
    
  • 
    

    Lymphoma

  
  
  
  
• 
  

  In adults

  
  
  
  
  • 
    

    Multiple myeloma

  
  

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