CHAPTER 43 RADIOGRAPHIC EVALUAIION OF BONE TUMORS Doug S. Lister, D.PM. The plain film radiograph is commonly the first objec- Third through Fifth Decade tive evidence to suggest a bone tumor. However, a Benign Malignant definitive diagnosis is rarelymade with a plan radiograph Aneurysmal Bone Cyst Adamantinoma alone, and must be comelated with clinical data and tl'rc Chondroblastoma Chondrosarcoma results of pathologic examination of the specimen. Chondromyxoid Fibroma Ewing's Sarcoma Radiographs of the area in question will assist Desmoplastic Fibroma Fibrosarcoma the pathologist in making the diagnosis. Errors in Giant Cell Tumor biopsy technique, bone infection, fracture callus Hemangioma formation, and poorly differentiated lesions may Lipoma complicate making the correct diagnosis. Proper Neurilemmoma evaluation of the x-ray is the first step toward diag- Non-ossifying Fibroma nosis, and a systematic approach is suggested to Osteoblastoma evaluate the bone lesion. Osteoma The basic method of evaluating a bone tumor Osteoid Osteoma on x-ray is to describe the morphological charac- Osteochondroma teristics, assess the aggressiveness of the lesion, Simple Bone Cyst and combine this data with clinical information in order to form a differential diagnosis. Important Greater than Sixth Decade clinical information to obtain includes the patient's Benign Malignant age, chief concern, symptoms, and medical history. Lipoma Chondrosarcoma The single most helpful portion of the history, in narrowing the differential diagnosis, is the age of the patient. certain bone tumors tend to appear in RADIOGRAPHIC CATEGORIES specific age ranges of patients (Table 1). Lodwick developed a computer-assisted approach Table L to formulate a differential diagnosis for the evalua- tion of bone tumors. He described four categories PATIENTAGE RANGES FOR of information to be obtained from the plain radi- DIFFERENTIAL DIAGNOSIS OF ograph: type of bone destruction, proliferation of bone, mineralization of tumor matrix, BONE TT]MORS and location inciuding dimensions of the tumor. Each category First and Second Decade helps to define the morphologic characteristics of Benign Malignant the bone tumor in order to formulate a reasonable differential diagnosis. Aneurysmal Bone Cyst Adamantinoma Chondroblastoma Ewing's Sarcoma Destruction of Bone Desmopolastic Fibroma Osteosarcoma Enchondroma There are three types of bone destruction that may Giant Cel1 Tumor be present in bone tumors: geographic, moth- Neurilemmoma eaten, and permeative. A geographic pattern of Osteoblastoma bone destruction is characterized by complete Osteoid Osteoma destruction of bone to the boundary between Osteochondroma tumor and normal bone. There is a well-defined Osteoma focal margin with a sharp transition zone between Simpie Bone Cyst the lesion and normal bone. Geographic bone 228 CHAPTER 43 destruction is most often associated with benign lesions. The differential diagnosis includes Ewing's tumors. The differential diagnosis should include sarcoma, fibrosarcoma, chondrosarcoma, and lipoma, osteoblastoma, osteoid osteoma, chon- osteomyelitis. droma, osteoma, fibrosarcoma, giant cell tumor, Combinations of the above patterns can exist, and osteomyelitis (Table 2). and a particular pattern may be distinguished by location within the bone. Geographic destruction Table 2 is primarily located centrally, while moth-eaten and permeative types of destruction are located PATTERNS OF BONE DESTRUCTION peripherally. Geographic Proliferation of Bone Chondroma Proliferative changes usually take one of two Osteoma forms: changes which reflect encapsulation, such Fibrosarcoma as an expanded cortical shell with a sclerotic rim, Lipoma or changes demonstrating a disseminated tumor Osteoid Osteoma without effective encapsulation, such as mottled Osteoblastoma proliferation. Both forms of proliferation are asso- Moth-Eaten ciated with periosteal and endosteal responses. Chondrosarcoma Trabeculation of the tumor may also occur. Ewing's Sarcoma Periosieal proliferation occurs as the addition Fibrosarcoma of layers of new bone are added to the exterior, Osteosarcoma creating an expanded osseous contour. The ulti- Permeative mate thickness of the surrounding cortical bone is Chondrosarcoma dependent upon the extent of endosteal erosion Fibrosarcoma and the degree of periosteal proliferation. Five Ewing's Sarcoma types of periosteal responses have been described: buttressing, onion-skinning, Codman's triangle, and hair-on-end appearance. The moth-eaten pattern of bone destruction is sunburst, buttressing occurs when the inter- more aggressive than that seen in the geographic Periosteal expanded cortex is "filled variety. It is characterized by multiple, small, con- face befween normal and proliferation merges with the fluent holes involving the outer cortex and inner in" with bone. Bony producing appezrance of structure. There is a large transition zone between underlying cortex an dense cortex. An onion-skin pattern is character- the lesion and normal appearing bone with a formation. poorly-defined margin. Unfortunately, lesions ized by multiple layers of new bone concentric layers of periosteal bone demonstrating this type of bone destruction are These multiple "onion peel" appearance, often rapidly-growing, malignant bone tumors. The create a lamellated, or associated with a more rapidly grow- differential diagnosis of a lesion demonstrating this and may be triangular pattern of bone destruction must include fibrosar- ing tumor. Codman's triangle is a periphery of a bone coma, chondrosarcoma, osteosarcoma, Ewing's elevation of periosteum at the of periosteal reaction may be seen sarcoma, but also osteomyelitis. tumor. This type lesion, as well as osteomyelitis. A permeative pattern of bone destruction is with an aggressive as delicate rays of characterized by many tiny holes throughout the These patterns appear blood cortex of the bone overlying the lesion. The transi- periosteal bone formalion, separated by tfi4ten rays extend tion zone is faint and often indistinguishable. The vessel-containing spaces. the radiating pattern from a margins of the lesion tend to blend with the sur- away from the bone in a pattern. rounding normal bone. Complete discontinuity in single focus, it is described as a sunburst to the under- the cortex may result in a secondary pathologic \7hen the rays extend perpendicular hair-on-end periosteal pattern is fracture. This complication may also occur as a lying bone, a hair-on-end periosteal result of moth-eaten patterns of destmction. This described. Sun-burst and aggressive tumors type of bone destruction is usually associated with reactions are associated with very aggressive and rapidly growing malignant such as Ewing's Sarcoma and osteosarcoma. CI]APTER 43 229 Trabeculation represents new bone formation dromas, solitary bone cysts, and chondroblastomas. as a secondary response to a nearby neoplasm. Eccentrically-located lesions are positioned to one Such proliferation is frequently located at the inter- side of the central axis, usually appear in the face between the endosteal and periosteal medullary canal, and include giant cell tumors, envelope. Descriptors of trabeculated lesions osteosarcomas, chondrosarcomas, fibrosarcomas, include thin, thick, delicate, coarse, loculated, stri- chondroblastomas, and chondromloroid fibromas. ated, and radiating. Examples of tumors with Cortically-located lesions are also found to one side trabeculated lesions include giant cell tumor, chon- of the central axis, but are primarily within the cor- dromyxoid fibroma, non-ossifying fibroma, tex. This location is typical for a non-ossifying aneurysmal bone cyst, and hemangioma. fibroma or osteoid osteoma. \X/hen a lesion appears on the outer surface of the cortex, it is considered tr'dinetafization of Tumor Matrix parosteal or juxtacortical, i.e., osteochondroma, Visible tumor matrix is associated with neoplastic parosteal osteogenic sarcoma, and .juxtacortical bone, but must be differentiated from calcifications chondroma. that may develop in regions of necrotic or degener- Location within the epiphysis, metaphysis, or ative tissue, cailus formation, or as a sclerotic diaphysis determines the longitudinal position. response to non-neoplastic bone. Calcified tumor Epiphyseal lesions include chondroblastoma, matrix is suggestive of cartilaginous tumors and may osteoma, intraosseous ganglion, osteoblastoma, include chondromas, chondroblastomas, chon- and osteoid osteoma. Metaphyseal lesions include drosarcomas, and chondromyxoid fibromas. The chondromlxoid fibromas, desmoplastic fibroma, matrix is usually centrally located, with concentric, osteoma, Ewing's sarcoma, giant cell tumor, flocculent, or random flecklike radiodense areas. lipoma, malignant fibrous histiocytoma, non- Osseous tumors which may demonstrate a vis- ossifying fibroma, osteoblastoma, osteochondroma, ible matrix include osteosarcoma, parosteal osteoid osteoma, chondromasarcomas, fibrosarco- osteogenic sarcoma, ossifying fibroma, osteoma, mas, osteosarcomas, and simple bone cyst. and osteoblastoma. The matrix is variable in size, Diaphyseal lesions include adamantinoma, and in comparison to cartilaginous tumor matrix, aneurysmal bone cyst, desmoplastic fibroma, demonstrates increased density, larger distribution, enchondroma, fibrous dysplasia, non-ossifying and a homogeneous consistency. fibroma, osteoblastoma, osteoid osteoma, Ewing's Lodwick states that a mature bone-forming sarcoma) and simple bone cyst. tumor,