Evaluating bone lesions in the pediatric population

My daughter Carolyn came to visit recently and I was surprised to see what she was studying for her next exam at St George’s University Medical school. She asked me to review the material with her. She was dealing with certain bone pathologies. I reviewed with her the material submitted by her faculty. I thought I should try now to review most of the bone lesions in the pediatric population. Perhaps in bringing a little of what I learned in my experience as an orthopedic surgeon and as a medical student. In anyway, I reviewed the chapter with her in the best of my ability. I promised her that I would try to explore with her a little more, the topic, so she would be able to master well most of the pediatric bone lesions.

Bone abnormalities are generally incidental on pediatric radiographs and are not common for the general orthopedist. Although the majority of the lesions encountered are benign in nature, the examining physician should keep in mind that the lesions can also be aggressive and represent a more concerning diagnosis. When evaluating such lesions, it is important to have in mine, the clinical history and the findings of the physical examination, and certainly the characteristics of the bony lesions. Often, the diagnosis can be obtained just by this simple evaluation. It becomes important to the examining physician to know if his level of expertise can allow him to treat the lesion or to refer the patient to a pediatric orthopedist or to an orthopedist-oncologist.

As we already discussed, bone lesions in the pediatric population are not uncommon. Most of these lesions are found on radiologic images obtained for other reasons by non-specialists. The majority of these lesions are benign in nature and this is the reason why a general orthopedist or a pediatric orthopedist should sharpen their knowledge on reading the radiologic findings, because often they may be the one performing the definitive treatment as well.

Generally, a lesion is identified on radiographs because of painful symptoms or the discovery of a mass which often can be attributed to a sport injury prompting the radiographic study. The incidence of malignancies in children is less than 5 cases per million for an osteosarcoma and less than 3 cases per million for an Ewing Sarcoma or any neuroectodermal tumor (pNET). The rate of bone and joint tumors has increased to 13% in the recent decade. Benign bone lesions such as metaphyseal fibrous defect are much more common and can be seen in 3% of children. They can be frequently osteochondroma (30%), bone cysts (28%), enchondromas (12%), osteoid osteomas (11%), non-ossifying fibromas (6%). Many of these lesions remained asymptomatic or even disappear with time. This is why it is difficult to know well the incidence.  Based on the fact that such benign tumors may remain asymptomatic for longtime, often when they are discovered, they can be quite large because of a poor work-up by the primary care physician.

Slow growing lesions are stable in size and less concerning for malignancy that the rapidly growing lesions. A painful lesion can point toward a malignancy sometimes. Night pain is common with osteosarcoma (79%) for more than 6 months until it is discovered. Pain at rest is often seen with Ewing sarcoma. Not all lesions with night pain are malignant, A well-known bony lesion Osteoid Osteoma is known to produce night pain easily relieved by anti-inflammatories medication. They are benign in nature and easily treated with the curettage of the “nidus”. Pathologic fractures are commonly seen with Bone Cysts like Unicameral Bone Cysts or enchondromas especially with their sizes.

Unicameral Bone Cyst

All bony lesions associated with weight loss, fever or fatigue should point the examining physician toward a diagnosis of infection or malignancy. A past medical history coupled with the patient medical history should allow the physician to round up toward a diagnosis, especially if there is a family history of p53 germline mutation by example and a diagnosis of osteosarcoma can be ruled out. Other patients with multiple hereditary exostosis (MHE) or Ollier’s disease or Maffucci’s syndrome have a predilection for developing a chondrosarcoma.


Non-Ossifying fibroma

A detailed physical examination on a young pediatric patient will help the examiner to perform a workup. Tenderness near the suspected lesion, the location, the range of motion of the joint need to be considered. An abnormal gait or the involvement of the neurovascular bundles can be seen with benign (osteochondromas) as well as malignant lesions. The lesions can be multiple in which case it is almost always a benign process like with the enchondroma. Simultaneously, the sites of the lesion can be by the contrary a sign of an aggressive lesion like with an osteosarcoma or a metastasis. Most of the malignant lesions like Ewing or Osteosarcoma have the tendency of invading the lower extremities around the knees, pelvis or the spine.

Enneking always tought us that 4 questions need to be asked: Where is the tumor, What is the tumor doing to the bone, what is the bone doing to the tumor, can you asset a histologic diagnosis.

Any associated skin lesions should be recorded since the pathologic fracture may be protruding through the skin, exteriorizing the infection or the tumor. Local erythema or inflammation may be present with Ewing;s sarcoma, eosinic granuloma or infections. A complete blood test with differential, a sedimentation rate and a C-reactive protein will assure the diagnosis of metatsatic lesion or infection especially when multiple bone lesions are present. Ewing’s sarcomas and lymphomas may present with white blood cell elevation or inflammatory markers while 50% of osteosarcoma have a tendency in exhibiting an elevation in alkaline phosphatase.

The radiographic examination has it importance. Often the apparence of the radiographs can give you a clue on the diagnosis of such lesions as a simple bone cyst, or an enchondroma, a non-ossifying fibroma or an enchondroma. The physician should pinpoint the location of the lesion in the metaphysis, the diaphasis or the epiphysis and the size. Remember well that bony expansion, erosion or permeation are signs of aggressivity to look for in a tumor. Some lesions may be lytic or blastic and the bone may react to the aggressivity with sclerotic edges or periosteal reactions. The radiographs may provide more details on the matrix of the lesion as well: radiolucent for a cyst, stippled calcification for a cartilage lesion, smoke-like or sclerotic lesions in soft tissue tumors invading the bone. Lesions larger tha 5 cm are almost always more aggressive. Some tumors may expand to the soft tissues like for the Ewing’s Sarcomas and the osteosacomas.

Benign lesions have tendency in showing well defined or sclerotic borders as well as a sharp transition zone and a lack of periosteal reaction while more aggressive lesions will show poor definition, bony destruction, periosteal reaction and occasionally soft tissue involvement. If a lesion older than 5-6 months has not shown any change, it is a lesion less likely to be aggressive (osteochodroma, non-ossifying fibroma etc.)






Non-ossifying fibroma

 Non-ossifying fibroma (NOF) is the most common benign tumor and is caused by an abnormal area of ossification and represent the most common benign lesion seen in kids between the age of 5 and 15. They are generally asymptomatic and found incidentally. In rare occasions, they maybe associated with Neurofibromatoosis or Jaffe-Campannacci syndrome , a congenital condition presented with mental delay, heart, eyes and gonad anomalies associated to the non ossifing fibromas.These lesions can be also isolated. Radiographs are tipycal with the demonstration of metaphyseal bubbly lesions. Some of the lesions may resolve with time but rarely may increase in size, in which case a biopsy may be needed.

All lesions unable to be recognized on plain radiographs require advanced imaging modalities like CT and MRI studies. CT is the best study to evaluate a bony lesion. Cartilage lesions will be bright on T2 images. MRI is usefull to evaluate lesion involving the marrow and should be performed prior to a biopsy. Whole body MRI imaging have been used in the evalation of pediatric malignancies and in trauma. PET-MRI may show in the future to be a superior technique. Bone scan and PET Imaging as well as PET-CT are being used in infections as well as in oncology work-up. PET-CT in my hands have shown the best in detecting metastatic lesions. This will avoid repeating the biopsies, additional therapies or surgical resections, and or additional radiation or chemotherapies. The surgeon performing the biopsy should expect a dry surgical field to avoid contamination with the soft tissues.

Ostoeochondroma are a benign chondrogenic tumor and the most common benign tumor deriving from aberrant cartilage. More common around the knee joint and may rarely be painfull and present with swelling. These lesions can be unique or multiple (MHE) like in a hereditary form  and may compress nerves in the area. They maybe sessile or pedonculated. Large lesions need to be removed especially if they appear after puberty and increase in sise rapidly. Some entities believe that such large lesions may be predictors of malignancy. More all osteochondroma have a cartilage cap which needs to be removed once curgical treatmment is offered because, if left behind, there will be a site of recurrence of the lesion.






Pedonculated and sessile osteochondromas


Eosinophilic Granuloma is generally a single lesion found in very young patients, less than 5 years old. This tumor can be associated with Lettewer-Siwe disease or Hand-Schuller-Christian Disease with life-threatning conditions. Alone, the eosinphilic granuloma has shown 100% survival with or whitout therapy. Eosinophilic granuloma is generally a painful lesion with swelling, able to impose an antalgic gait to the young patient between the age of 1 and 4. These lesions can mimic other lesions and can be present at any location. Imaging can also reveal a soft component of the tumor. On histologic evaluation, there is a lack of nuclear atypiawith a majority of mononuclear histyocytes-type cells with a coffee bean shaped nuclei, remebering a tennis shape racket. These lesions can be observed, injected with cortisone or curetted with or without bone grating. Occasionally radiation therapy and/or chemotherapy have been used in the treatment of such lesion. Many of us will use observation and if needed curetage of the lesion.



Eosinophillic Granulomas of bone


Aneurysmal bone cysts (ABC) are also benign bone lesions, with a tendency to be expansile and filled with blood but seperated with fibrous septae. They may present with pain and a sensation of fullness. They often exhibit pathologic fractures. Plain radiographs, MRI and biopsy are always needed to asset the diagnosis. These lesions can change in telengiectatic osteosarcoma and need the attention of an orthopedist-oncologist. Similarly, unicameral bone cysts (UBC) are simple bone cyst formed by a failure of the medullary bone. Very commonly seen in the proximal humerus metaphysis of the adolescent, the bone weakens and may present a pathologic fracture with any minor trauma. Radiographs showed a central lytic metaphyseal lesion expanding the cortices and a typical sign to look for in case of fracture: “The fallen leaf sign” which represent the fractured cortex fallen into the buttom of the cyst. The appropriate treatment of an UBC is observation if asymptomatic, and splinting or any protective gear like an arm sling , crutches when the proxila femur is involved, to allow the fracture to heal.  If the lesion persists after bone union, steroid injection treatmenthave been successful in healing the cyst or curetage and bone grafting if needed. Generally these cysts have the tendency of disappearing after the healing of the pathologic fracture.


Aneurysmal bone cyst


Let us review also two malignant bone lesions:

Osteosarcoma is a malignant lesion of bone encountered in children at around 5 per million during the second decade of life. Often the diagnosis is made after an initial complaint associated with a banal sport injury.  X-Rays and MRI of the entire bone involved should be requested especially when skip lesions are involved. Commonly found around the knee or shoulder joint. Radiographs may demonstratelytic or blastic characteristics. An importat finding of a sunburst appearance or a Codman triangle may be seen on the radiographs. Biopsy is always necessary and is better done by the one performing the definitive diagnosis. Treatment consists in wide surgical resection combined with pre and post-operative chemotherapy treament. It is believed that at the time an Osteosarcoma is diagnosed, the patient has already suffered from metastasis especially to the lungs. Long-term survival  rates ranging from 70% to 30% are seen in some institutions with advanced metastasis under modern chemotherapy treatments.


Osteosarcoma of bone


Ewing’s Sarcoma is a small round cell malignant tumor that is commonly diagnosedin the second decade of life bot can occasionally seen in the 40’s. the clinical findings can vary with a painfull growing mass most commonly aorund the knees, pelvis and the spine. The lesion may appear lytic and permeative with a classic “onion’s skin-appearance. MRI is the best imaging modality to use. The lesions need to be biopsied to assure a definitive diagnosis like in the osteosarcoma. A bone marrow biopsy is mandatory in order to stage such lesion. The treatment is based on chemotherapy and wide surgical resection. Under the age of 15, a 70% of survival rate is seen. Limd-salvage procedure are occasionallt offered when the disease is discovered at an early stage.

In Haiti, we have seen more of those malignant tumors during the winter months. I have witnessed during my 3 years of residency at the HUEH more than anybody else may discover in a lifetime. The parents will bring such patient in a wheelchair because of a recent episode of shortness of breath. They just did not realize that the reason for such changes is because the patient has developped metastasis to the lungs. Such “orthopedic disease” is seen by the paysant, like a malediction of the Gods and these kids are neglected and placed in a room or a corner until it is too late. Finally, they present him/her to the hospital for final care. I do not need to add that what we were unable to offer subtantial help at the late stages but often we may perform an “amputation for the property” because the extremity has become so heavy that its weight on the bed or the floor has engendered a deep ulceration with further infection. This bought tears to my eyes when during the year 1976, I saw my first case of Osteosarcoma in an 18 year-old gentleman, with difficulty in breathing and cachxic. The left knee had an osteosarcoma with ulceration of the skin. He was in a wheelchair. No textbook has ever presnted such pictures of a knee as large as a cow head because of malignant bone disease.








Ewing sarcoma


In conclusion, I want to repeat that bone tumors are frequently seen in the pediatric population. Often, the patients will present a story related to a trauma due to a sport injury. It is a way for them to explain the long-standing symptoms. From that point, they may be poorly managed by an inexperienced physician not properly examining the patient  or simply not requesting the proper radiographs. I have seen kids beeing diagnosed with growing pain or contusions or patellofemoral pain syndrome with a consistant pain for weeks or months. It is never a mistake to request a radiographic study which will give you an explanation for the symptoms: a benign or a malignat process? Many lesions which may be discovered on X-rays, may requiere an MRI study and surely perhaps may warrant a biopsy. In this case, do not hesitate to refer such patient to a orthopedist-oncologist in case of doubt.


Case of Osteosarcoma distal femur ( Haiti 1977).                                                                                                                                            I leave you all with this case: An unusual case of Osteosarcoma which I treated during my orthopedic residency in Haiti at the HUEH 1976-1979, in an 18-year-old gentleman whom parents bought to the hospital for orthopedic care. I certainly will guaranty that you will never have the opportunity to examine such a patient anywhere else. He came to us with extensive pulmonary metastases in a terminal phase and this large knee mass was as well macerated from the weight ot the extremity in contact-surface on which he was resting his extremity on, at home on the floor or on the bed.

NB: I wrote this page especially for my daughter Carolyn Lara Coles presently at the end of her second year of medical school at St georges University and also for all the residents back home and in the United States who have benefited from my teaching. So they may remember the way to diagnose bony lesions in the perdiatric population.



Maxime Coles MD

Boca Raton FL  (8-26-21)



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