REVIEW ARTICLE

Benign Tumors of Bone

Subbarao K

Padmshri Prof. Dr. Kakarla Subbara, Hyderabad, India.

Benign tumors of bone are common while applied in the diagnosis of bone tumors are malignant tumors are rare. Benign tumors given in table III constitute about 75% of all bone tumors excluding metastasis. Most of these tumors Table III: General principles applied in the do not need surgery as diagnosis is made on diagnosis of bone tumors. plain films. 2% of all benign tumors may Age and Sex undergo malignancy. Several of these bone Single or Multiple Lesions tumors present clinically with pain, swelling Type of Bone involved and symptoms of compression of vascular Site of the lesion within the bone and neural structures. Many of them present with history of trauma and a pathological Site of origin of the lesion fracture. Some of them are called as “leave Nature and extent of bone change me alone” lesions as biopsy or surgery is Appearance of the transitional zone unnecessary. The following table I gives Nature of the tumour matrix the classification according to the tissue of Type of periosteal reaction origin Soft tissue involvement

Table I: Classification of benign tumors of The radiological findings in a benign tumor bone according to the tissue of origin. include narrow transitional zone, well Osseous tissue defined border, intact periosteum and Cartilaginous tissue minimal soft tissue swelling: Fibrous tissue Vascular tissue Tumors of osseous tissue include osteoma, Miscellaneous, lipoma etc., osteoid osteoma, osteoblastoma etc., osteomas constitute condensed bone with Radiological investigations include the well defined border. They are more common following table II: in para nasal sinuses, skull and long bones (Fig.1ab). Most of them are detected Table II: Radiological investigations incidentally. They should not be mistaken Conventional for bone island, however large they may be Ultrasonography (Fig. 2ab). Osteomas of the frontal sinus may erode the bone and produce MDCT pneumoencephalocele. Potential of Pet CT malignancy does not exist (Fig.2c). Radionuclide scanning Multiple osteomata with intestinal polyposis MRI goes with the name of Gardner syndrome (Fig. 3). All these investigations may not be necessary in any given patient. The general principles

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OSTEOID OSTEOMA bodies. Diaphysis of long bones is also a common site. The other sites are less Osteoid osteoma occurs in first four decades common. of life and is more common in men. 2/3rd effect appendicular skeleton specially Radiological features include a large nidus proximal and distal segments of femur and more than 2cm in diameter. New bone proximal half of tibia. Computed formation occurs with periosteal reaction Tomography (CT), isotopic scanning and specially in long bones. MDCT plays a MRI may be necessary to confirm the major role in identifying osseous matrix (Fig. diagnosis and to demonstrate the nidus (Fig. 11 & 12). Aneurysmal bone cyst may 4abc). It is less common in axial skeleton. superimpose and may be associated with Skull and facial bones are affected very osteoblastoma. In long bones, periosteal rarely. Morphologically and anatomically reaction may be prominent (Fig. 13). there are four types table IV: CARTILAGINOUS TUMORS Table IV: Morphological and anatomical location of Osteoid osteoma: Cartilaginous tumors constitutes major of all Intra Cortical the benign tumors. The classification of Periosteal these tumours is included in the table V: Spongiosal Subarticular Table V: Classification of Cartilaginous Tumors. The essential point in the radiological MONOSTOTIC diagnosis is the identification of central Enchondroma calcifications surrounded by ovoid Osteochondroma translucency. The average diameter of the Juxta Cortical chondroma nidus is between 5mm to 1.5cm (Fig. 5). If Periosteal chondroma the nidus is more than 2cm it belongs to the Chondroma protuberans category of osteoblastoma. Intracortical Chondroblastoma osteoid osteoma produces dense sclerosis Chondromyxoid Fibroma around the nidus. Subperiosteal type Post traumatic produces periosteal reaction while spongiosal type produces very little reactive bone (Fig. POLYOSTOTIC 6). Subarticular osteoid osteoma simulates arthritis as it produces synovial reactions (Fig. Multiple enchondromata 7). In the vertebra it occurs in the neural arch Metachondromatosis (Hereditary) and produces scoliosis due to pain. CT Ollier’s dyschondrodysplasia scanning is essential to identify the nidus (Fig. Maffuci’s Syndrome 8). Multiple osteochondromata It is of significance that CT and MRI play a better role than three phase technetium 99mm Diagnosis of chondroid tumours mainly rests isotopic scanning (Fig. 9ab and 10) on conventional radiology and is made by the anatomical location, transitional zone and OSTEOBLASTOMA mineralization of matrix. The calcified matrix may be minimal or heavy. When Osteoblastoma is encountered in the first four there is no mineralization of cortex, it is decades of life but common in 2nd and 3rd difficult to make a firm diagnosis. In these decades. The sites of predilection include instances CT or MRI may be helpful. neural arches of spine as well as the vertebral Endosteal scalloping, thick periosteal

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Fig.1a: Osteoma in left Fig.2c: CT Ethmoid Fig. 4b: CT of femur of frontal sinus osteoma with pressure same patient showing on the eye ball. the nidus.

Fig. 6: Spongiosal type of osteoid osteoma in tibia producing minimal reactive bone

Fig.1b: Lateral view of skull showing large osteoma of frontal sinus.

Fig.3: Flat osteoma of Fig.4c: Technetium femoral shaft in 99mm scanning showing Fig.7 : Subarticular Gardner syndrome with hot spot at the site of osteoid osteoma (arrow) polyposis coli. osteoid osteoma. with widening of the joint space due to synovitis.

Fig.2a: Bone Island (Insular compacta)

Fig.8: CT of spine showing osteoid Fig.2b: Giant bone Fig.4a: Intracortical Fig.5: Osteoid osteoma osteoma(target sign) island in iliac bone osteoid osteoma. in the distal phalanx of Dense reactive bone the thumb with central obscures the nidus. calcification.

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reaction and cortical hook when present may and central nervous system. The diagnosis of add to the correct diagnosis. Maffucci syndrome is made by the presence of enchondromata and presence of ENCHONDROMA phleboliths in the soft tissue hemangiomas (Fig. 21). It is generally asymptomatic except when there is a trauma where a pathological Soft tissue chondromas are also encountered fracture is present (Fig.14). The age is without the involvement of underlying bones. between 10 – 30 yrs. When multiple these They show amorphous, lumpy and are located in tubular bones of hands (Fig.15). homogenous calcifications (Fig.22ab). They Multiple enchondromata in the hands is also may be seen in intra and extra articular called Ollier’s syndrome. Other sites include locations (Fig. 23ab). long bones including ribs (Fig. 16abc). Enchondroma is located during the central Ollier’s dyschondroplasia is developmental medullar canal in the metaphysis. The in nature. Chondromatous lesions are incidence is 3-17% of biopsied primary bone encountered in several bones. The age range tumors and it is second most common is between 1 to 12 yrs. These lesions are cartilage containing tumor. Etiology is generally distributed on one side of the body. continued growth of residual benign rests of These may lead to shortening of the limb. cartilage displaced from the growth plate. Radiological findings include cortically The calcifications of the matrix may assume oriented lesions with calcifications. The the shape of punctuate, arc like, circular, hook sign indicates that it is cartilaginous nodular, or a mixture of these (Fig. 17ab). lesion. This lesion prevents normal growth Another finding in cartilaginous tumors is the of the bone and may lead to shortening of the presence of a hook at the margins which has bone (Fig. 24ab). not been described in the literature (Fig. 18). Chondroblastoma is a benign cartilage tumor Periosteal chondroma is also called juxta and constitutes 1-3% of all bone tumors. cortical chondroma and is diagnosed by the Male and Female ratio is 2:1 and is anatomical location and the presence of encountered in 2nd & 3rd decades. Long & calcific matrix (Fig. 19ab). short tubular bones are frequently affected. Radiologically a lytic area is noted in the The complications of enchondroma include epiphysis or metaphysis, or the lesion may pathological fracture and malignant involve both epiphysis and metaphysis. degeneration particularly in long-bone Chondroid calcification is present in 1/3rd of enchondromas and the incidence is between cases (Fig. 25ab). When it is primarily 15 and 20%. In the differential diagnosis, located in the metaphysis periosteal reaction epidermoid inclusion cyst (phalangeal tuft), may be noted (Fig. 26). In about 1/3rd of the with history of trauma, unicameral bone cyst cases aneurysmal bone cyst may be (rare in hands, more radiolucent), giant cell associated, MRI helps in demonstrating fluid tumor of tendon sheath (commonly erodes – fluid levels (Fig. 27ab). bone, soft-tissue mass outside bone) fibrous dysplasia (mostly polyostotic) and bone Chondromyxoid fibroma is a rare benign infarct (Fig. 20ab). cartilaginous tumor although it is also included in fibrogenic tumors. It is Maffucci syndrome constitutes multiple encountered in 2nd and 3rd decades. It occurs enchondromata and soft tissue hemangiomas. in the metaphysis of long tubular bones as It is actually a non hereditary mesodermal well as short bones of the feet. dysplasia. There is increased prevalence of Radiologically, it is a lytic expanding lesion malignancies in the bone, ovary, duodenum tending to be eccentric. Trabeculations may

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Fig.12: CT – osteoblastoma lumbar spine. Note the large lytic area with new bone

formation. Fig. 15: Multiple enchondromata in the hand.

Fig. 9ab: CT showing a tiny osteoid osteoma which is missed on radiographs.

Fig 16a: Enchondroma in Clavicle. Fig.17ab: Calcified enchondromata, a. head of fibula, Fig.13: Osteo- b. intertrochanteric blastoma with a large area of femur. lytic area with periosteal

reaction in the proximal end of humerus.

Fig 16b: Enchondroma in patella. Fig. 10: MRI femur showing the nidus in osteoid osteoma.

Fig.14: Enchondroma of Fig.11:Osteoblasto-ma fifth metacarpal with Fig.18: Intracortical with large lytic area in pathological fracture. chondroma showing the lamina of thoracic calcifications and the vertebra with irregular presence of hook osteoid matrix. Fig 16c: Enchondroma inferiorly. in big toe.

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Fig. 19: Peristeal Fig. 21: Maffuci chondroma in the syndrome. Note the phalanges. enchondromata and calcified phleboliths in Fig. 25ab: hemangiomata. Chondroblastoma in a. humeral head, b. lower end of femur. Fig. 23ab: Intra articular chondroma of the knee.

Fig. 26: chondroblastoma with periosteal reaction at the base of the fifth Fig. 22ab: a. heel, b. metacarpal. Note the hand – Soft tissue pathological fracture. enchondromata.

Fig.24ab: Ollier’s Fig. 20ab: AP and dyschondroplasia – a. Lateral views of lower hand, b. femur. Note end of femur showing the hook sign as well as bone infarct. the enchondromata. Calcification simulates enchondroma.

Fig. 27ab:

Chondroblastoma of calcaneum. a. plain film, b. MRI showing fluid – fluid levels indicating secondary ABC.

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be seen with endosteal sclerosis (Fig. 28). Trevor’s Disease (Dysplasia epiphysialis This is one of the benign aggressive lesions hemimelica) is a disorder with eccentric simulating radiologically an aneurysmal bone growth of ossification centre associated with cyst. Calcification is rarely noted, although calcified mass. It may be considered as punctate calcifications are noted epiphyseal osteochondroma. This may be histologically. Advanced imaging does not hereditary. Deformity of joint may develop. really help in the diagnosis. Generally, monoarticular but more than one joint may be affected. Talus and distal Solitary osteochondroma (exostosis) is femoral epiphyses are most commonly generally encountered in the first four involved. Radiologically, focal calcifications decades. When a single lesion is noted it is occur at the epiphysis or apophysis. Affected appropriate that the whole body is centres may become hypertrophied resulting investigated for detecting multiple lesions. in severe deformities (Fig. 34abc). Radiologically, it occurs in the metaphysis and diametaphysis and projects out of the Synovial chondromatosis may be primary or underlying the bone. It may be sessile or secondary. Primary synovial chondromatosis pedenculated. The femora and tibia are may be intra articular or extraarticular (Fig. common sites. The medularic cavity is in 35). Secondary synovial chondromatosis is continuity of the parental bone. In long due to advanced degenerative arthritis. The bones these lesions grow away from degenerated and fragmented cartilage and metaphysis. Growth takes places in the synovium may be separated and form a cartilaginous cap. Growth, generally nidus for secondary synovial diminishes after skeletal maturity (Fig. osteochondromatosis. Primary synovial 29abc). chondromatosis is due to metaplasia of the synovium which gets fragmented and Multiple osteochondromata (exostoses) are nourished by synovial fluid and eventually hereditary and autosomal dominant. These calcifies and ossifies and form are encountered in younger age groups. They chondromatosis. are bilateral and often symmetrical. Radiologically, the findings are that of Fibrous tumors of the bone are listed in table solitary exostosis. However, since they are VI developmental, shortening and deformity of limbs may be noted (Fig. 30abcd). Table VI: Fibrous tumors of the bone. Fibrocortical defect Complications include fracture, bursal Nonossifying fibroma formation, compression of nerves and vessels Ossifying fibroma and malignant transformation (Fig. 31ab). Desmoplastic fibroma While in solitary exostosis / Enchondroma Osteofibrous dysplasia the incidence of malignancy is 1% (Fig. 32) in multiple exostoses the incidence may go Fibromatosis upto 10 – 15%. In Maffucci syndrome the Neurofibroma incidence is 20 – 30% which includes non Fibrous dysplasia osseous tumors. Chondromyxoid fibroma

Post traumatic exostosis has been described Benign Fibrous tumors may include and when it takes the shape of a tent it is fibrocortical defect, nonossifying fibroma, named as Turret exostosis. Another exostosis ossifying fibroma and fibroxanthoma. is due to osteoperiostitis or Nora’s lesion as a Fibrocortical defects are developmental in sequel to trauma (Fig. 33ab). Post radiation nature and not really tumors. These are osteochondromata have also been described. common between 4 and 10 years and

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Fig. 29b: humerus. Note cauliflower like osteochondroma

Fig. 31ab: Fracture of the pedinculated exostosis

Fig. 29c: Sessile Exostosis of humerus seen end on

Fig. 28ab: Fig. 32: Benign Chondromyxoid enchondroma fibroma of a. proximal undergoing malignancy tibia, b. distal tibia in the lateral aspect eroding the cortex.

Fig. 34abc: Trevor’s disease involving a. Femoral head, b. Talus and c. Knee

Fig. 29a: Exostosis of lesser trochanter of Fig. 30ab: Bilateral femur osteochondromata. Note hook like projections

Fig. 35: Primary synovial chondromatosis of the shoulder. Fig. 33ab: a. Nora’s lesion due to osteoperiostitis, b. Turret exostosis due to previous trauma

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predominantly present in femur and tibia. resulting from avulsive injury of the adductor Radiologically, they appear as elliptical magnus musculofibrous segment. It is lucent defects with sclerotic rim (Fig. 36ab). located on the posteromedial surface of distal As the child grows these disappear end of femur (Fig. 41ab). Irregular new spontaneously. bone formation simulates osteogenic sarcoma. Biopsy also may be mistakenly reported as Nonossifying fibroma is the most common malignant bone tumor. benign fibrous lesion seen in 2nd and 3rd decades. It is classically seen at the Benign fibrohistocytoma is rare and metaphysis of long bones, generally in lower encountered in 3rd and 4th decades. limbs. A pathological fracture generally Radiologically, a lytic well defined lesion is brings the patient to medical attention. noted with narrow zone of transition. Sclerotic border may be seen and the lesion is Radiologically, a cortically oriented eccentric eccentrically located. It is believed to be a radiolucent defect with a narrow zone of regressed giant cell tumor. transition is noted. The margins are lobulated and sclerotic with multiple bone Fibroxanthoma is a histological diagnosis but ridges. More aggressive lesions persist to radiologically resembles fibrous dysplasia adult life and migrate to diaphysis. This is with a lytic area and dense rind (Fig. 42ab) one lesion that the radiologist should be firm in diagnosis and should not advise the Infantile Fibromatosis is seen in early surgeon to resect (Fig. 37ab), CT and MRI childhood. Radiologically, soft tissue are unnecessary. swellings are noted with metaphyseal defects in long bones. Minimal periosteal reaction Ossifying fibroma is encountered in the first may also be noted (Fig. 43ab). two decades and mainly involves tibia, although fibula may also be involved. The Chondromyxoid fibroma has been dealt in child complains of bowing of tibia. cartilaginous lesions.Fibrous dysplasia Radiologically, a well defined lesion with belongs to the category of skeletal mixed, lytic and sclerotic areas (Fig. 38ab), dysplasia. Hence it is not described here. affecting the middle third of the tibia and produces anterior bowing. Rarely Vascular tumors of bone are classified in peasudoarthrosis may develop. Spontaneous table VII. The most common lesion is resolution may occur. Surgical intervention hemangioma followed by often results in recurrence. When aggressive hemangiopericytoma. it may simulate osteofibrous dysplasia (Fig. 39). Table VII: Vascular tumors of bone. Cavernous nd rd Desmoplastic fibroma occurs in 2 and 3 Capillary decades. Long bones are mostly affected. Venous However innominate bone, scapula, mandible Glomus tumor and rarely spine may be involved. Hemangiopericytoma Radiologically, it is an aggressive lytic lesion with endosteal erosion and cortical expansion. Hemangioma of the bone is encountered in It may occur in the metaphysis and 4th and 5th decades. The vertebra is more diametaphysis. The zone of transition may common but skull, long bones, flat bones and be wide, it is difficult to make a firm soft tissues may be involved. It comprises diagnosis on plain films alone (Fig. 40). about 1% of skeletal neoplasms.

Radiological findings depend upon the site of Cortical desmoid is a tumor like lesion

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Fig. 37b:. Nonossifying fibroma in tibia with a fracture

Fig.40: Desmoplastic

fibroma of fibula difficult to differentiate from ABC

Fig. 42ab: Fibroxanthoma of femur Fig 36ab. Fibro Cortical defects. a. femur and tibia and b. tibia

Fig. 38ab: Ossifying fibroma involving cortex of middle third of tibia

Fig. 37a: Nonossifying fibroma in tibia.

Fig. 41ab: Cortical desmoid in the lower Fig. 43ab: Infantile end of the femur on Fibromatosis involving medial aspect due to shoulder and proximal avulsion injury of few ends of femora fibres of adductor magnus.

Fig. 39: Osteofibrous dysplasia with lytic and Fig. 44: Soft tissue sclerotic changes hemangioma with calcified phleboliths

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Fig. 46c: Hemangioma CT of skull

Fig. 49: MRI, Hemangiolipoma - T3 bright signal

Fig. 52a: Paraosteal lipoma of femur

Fig.50: Fig. 52b: Paraosteal Hemangiopericytoma lipoma of femur involving the tibia

Fig. 45ab: Hemangioma of lower end of femur

Fig. 53: Lipoma of calcaneum with central calcification

Fig. 47ab: Vertebral Hemangioma. a. plain, b. tomogram

Fig. 51: Lipoma shoulder with soft tissue calcification

Fig. 46ab: Hemangioma of skull. a. “Sun Burst” Fig. 48: CT – appearance, b. “spoke Hemangioma of wheel” vertebra. CT shows polka dot appearance

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hemangioma. Soft tissue hemangioma may be seen at the attachment to the shaft (Fig. show calcified phleboliths (Fig. 44). 52ab).

Hemangioma of a long bone shows Intra osseous lipoma is also rare and may honeycombing with vascular channels. occur in any bone. However, when it However, the radiological findings are not occurs in the calcaneum radiological classical (Fig. 45ab). appearance is classical. A lucent lesion is noted in the body of the calcaneum with Hemangioma of skull is often seen in frontal central calcification or ossification (Fig. 53). and parietal bones. Radiological appearances have been described under “spoke wheel”, Ganglionic cyst is often seen in adults in the sun burst or honeycombing patterns. Large subarticular area of joint. Radiologically, a vascular channels adjacent to the lesion may lucent lesion with sclerotic rim is noted be seen (Fig. 46abc). (Fig.54ab).

Vertebral hemangioma is more common Further Reading: particularly in elderly women. Radiologically, coarse vertical striations 1. Rockwell M.A. et al. Periosteal simulating corduroy or jail bar appearance Chondroma J. Bone Jt. Surg. (Am.) best seen in the lateral view (Fig. 47ab). CT 1972;54(4):102-108. appearance is characteristic and is called Polka dot appearance (Fig. 48). In MRI 2. Murray Ronald O., Jacobson Harold scanning bright signal is noted due to the G and Stoker Dennis J et al. The presence of fat (Fig. 49). Vertebral Radiology of skeletal disorders. 3rd hemangiomas are also called edition, Churchill Livingstone, New hemangiolipomas. Most of these are York, 1990. incidental findings. 3. David C. and Dahlin et al. Bone Cystic angiomatosis is a rare entity involving tumors. 3rd edition, Charles C Thomas, several bones with multiple hemangiomata. U.S.A., 1978. Sclerosing hemangiomatosis is also rare with major component being sclerosis due to 4. Greenfield GB: Radiology of Bone reactive new bone. Disease. Philadelphia, JB Lippincott, 1975. Hemangiopericytoma is another vascular lesion which produces mainly lytic areas with 5. Spjut Harlan J., Dorfman Howard D., presence of varied trabeculae. It may expand Fechner Robert E. And Ackerman the bone. It is difficult to diagnose on plain Lauren V et al. 2nd series; Tumors of films alone (Fig. 50) bone and cartilage, New York, 1971.

Miscellaneous lesions such as lipoma of soft 6. Resinick and Niwayama et al. tissue produces a lucent area in the plain Diagnosis of bone and joint disorders. films. It is well demarcated. Calcification 3 vol: Philadelphia,1982. may rarely be seen (Fig. 51). 7. Subbarao Kakarla and Satish K. Paraosteal lipoma is a rare tumor occurring in Bhargava et al. Diagnostic Radiology 4th and 5th decades. Radiologically, a lucent and Imaging, revised edition under superficial soft tissue lesion adjacent to print, 2012 – 13. cortex is noted. Calcification and ossification are common and periosteal proliferation may

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