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We will provide an imaging-focused discussion of 3 benign bone tumors that do not fit in the categories of cartilaginous tumors or osteoid tumors. We have chosen giant cell tumor of bone, unicameral bone cyst, and fibrous dysplasia. All 3 of these entities are common enough that one does not have to be a musculoskeletal radiologist in a cancer hospital to encounter them occasionally, but none of them should be seen frequently.

Clinical Presentation A 23-year-old healthy, female with no known medical issues presents to the dental clinic at Indiana University School of Dentistry. Cone beam computed tomography (CBCT) volume was acquired as part of a dental implant evaluation for the sites of teeth #9 and #10. Upon review, an incidental finding of a well-defined, irregular, nonexpansile, radiolucent lesion along the anteroinferior border in the body of the C2 vertebrae was noted. Differential Diagnosis The working differential of the area included (1) unicameral bone cyst, (2) giant cell tumor, (3) brown tumor, and (4) fibrous dysplasia. These all appear radiolucent, and most do not manifest symptoms and are found incidentally. An evaluation with a physician to assess for neurologic deficits or other related symptoms would be needed. Possible further imaging with contrasted multidetector computed tomography (MDCT), magnetic resonance imaging (MRI), and/or blood tests may also be considered. Because of the invasive nature, the possibility of surgical intervention including biopsy, curettage, or bone grafting should be evaluated by an orthopedic surgeon. Diagnosis and Management The patient was notified by the provider to evaluate the lesion, and further dental treatment has been deferred until a diagnosis can be reached. Discussion Incidentally, the provider did not fully read the report. It was through inquiry by the radiologist that the patient’s status was brought to the provider’s attention. This emphasizes how comprehensive evaluation of CBCT can bring to light potentially urgent conditions.

Simple and aneurysmal bone cysts are benign lytic bone lesions, usually encountered in children and adolescents. Simple bone cyst is a cystic, fluid-filled lesion, which may be unicameral (UBC) or partially separated. UBC can involve all bones, but usually the long bone metaphysis and otherwise primarily the proximal humerus and proximal femur. The classic aneurysmal bone cyst (ABC) is an expansive and hemorrhagic tumor, usually showing characteristic translocation. About 30% of ABCs are secondary, without translocation; they occur in reaction to another, usually benign, bone lesion. ABCs are metaphyseal, excentric, bulging, fluid-filled and multicameral, and may develop in all bones of the skeleton. On MRI, the fluid level is evocative. It is mandatory to distinguish ABC from UBC, as prognosis and treatment are different. UBCs resolve spontaneously between adolescence and adulthood; the main concern is the risk of pathologic fracture. Treatment in non-threatening forms consists in intracystic injection of methylprednisolone. When there is a risk of fracture, especially of the femoral neck, surgery with curettage, filling with bone substitute or graft and osteosynthesis may be required. ABCs are potentially more aggressive, with a risk of bone destruction. Diagnosis must systematically be confirmed by biopsy, identifying soft-tissue parts, as telangiectatic sarcoma can mimic ABC. Intra-lesional sclerotherapy with alcohol is an effective treatment. In spinal ABC and in aggressive lesions with a risk of fracture, surgical treatment should be preferred, possibly after preoperative embolization. The risk of malignant transformation is very low, except in case of radiation therapy.

Introduction There is no consensus on when and how to treat unicameral bone cysts (UBCs), partly because of a lack of knowledge of the aetiology. Purpose To review the different treatment techniques for UBCs and to describe our results with a single injection of autogenous bone marrow (BM) mixed with demineralised bone matrix (DBM) in very young children. Patients and methods We reviewed five patients under the age of 8 years with UBCs treated by percutaneous aspiration and a single injection of BM associated with DBM. The cyst was located in the proximal humerus in four patients and in the proximal femur in one patient. Assessment of the need for surgery was based on the clinical and radiographic suspicion of new pathological fractures. The administration of a second injection, when necessary, was based on the surgeon's judgement regarding the risk of fracture. The mean follow-up after first injection was 41 months. Results There were no complications related to the procedure, except a non-displaced fracture, which healed without problems. All patients were pain free and progressively resumed their activities without restriction until a new fracture occurred in two cases. According to Capanna's classification, only one case healed completely (grade 1), one lesion was classified as grade 2, and there were three recurrences at 11, 12 and 27 months after initial treatment (grade 3). The final outcome was treatment failure for three out of the five patients. Two patients were treated with a second injection and one patient is waiting for surgery. Conclusion A single injection of aspirated autogenous BM mixed with DBM in very young children with active UBCs at risk of fracture is very simple, comfortable and safe. Nevertheless, the results seem to be unpredictable and are probably more dependent on the natural evolution of the cyst than on the treatment. Further comparative studies with larger sample numbers are needed.

Simple bone cyst (SBC) also known as unicameral bone cyst is a benign, radiolucent bone lesion that is seen commonly in childhood. These lesions are usually found incidentally although pain and swelling can be seen. The most common complication is a pathological fracture, and this is often the cause of presentation. Here, we present a 22-year-old male with right lower quadrant pain due to SBC related pathological fracture of right iliac bone which is mimicking acute appendicitis. © 2018 Elsevier Inc.

Recently, surgical treatment of a symptomatic unicameral cyst of the proximal femur has been achieved with less invasive procedures than traditional open curettage with an autologous bone graft. In this article we introduce endoscopic surgery for a symptomatic unicameral cyst of the proximal femur. The presented technique, which includes minimally invasive endoscopic curettage of the cyst and injection of a bone substitute, not only minimizes muscle damage around the femur but also enables sufficient curettage of the fibrous membrane in the cyst wall and the bony septum through direct detailed visualization by an endoscope. Furthermore, sufficient initial strength after curettage can be obtained by injecting calcium phosphate cement as a bone substitute.

Chondromyxoid fibroma occurs primarily in the long tubular bones of the lower extremity, with the foot representing the second most frequent location after the knee. This benign cartilaginous tumor of bone is currently the rarest reported neoplasm of cartilaginous origin. This mass can mimic other benign and malignant bone tumors owing to its variable histologic features. We report 2 cases of chondromyxoid fibroma of the calcaneus with varying presentations. Initially, advanced imaging studies pointed to a diagnosis of a unicameral bone cyst. Pathologic examination is difficult but can be used to differentiate this lesion from more serious conditions. A quick and accurate diagnosis of chondromyxoid fibroma can prevent unnecessary treatment that could be harmful to the patient.

Unicameral bone cysts of the pelvis are extremely rare. A 19-year old man presented with a pathologic fracture through a pelvic unicameral bone cyst. He was treated with computed tomography-guided percutaneous curettage, biopsy, and demineralized bone matrix injection. Treatment has proven successful in short-term follow-up.

Summary The objective of this paper is to analyse the outcome of surgical therapy for neoplastic disease of the foot at our institution with special regard to limb preservation in malignant tumours. A retrospective study was carried out, follow-up 1–10 years, by the musculoskeletal oncology group (referral centre) at Ulm University. We present a series of 26 patients with 11 malignant, 14 benign and one ‘tumour-like' lesion treated between 1981 and 1994. A large variety of both benign and malignant histological entities were observed. The most frequently encountered diagnoses in the respective groups were unicameral bone cyst and fibrosarcoma. Therapy consisted of curettage or resection and grafting ( n = 11), marginal resection ( n = 3), wide soft tissue resection ( n = 3) or ray resection ( n = 4). In one case an open biopsy was the only measure performed. Two amputations of the forefoot were carried out, and in two patients an amputation above the ankle joint was necessary. Repeat surgery was required for secondary reconstruction of osseous defects, implant removal or bilateral disease. Among the variables analysed in this study were survival, local recurrence, pain, swelling, the need for orthopaedic footwear, limited walking ability and occupation before and after surgery. In most cases good function of the foot could be maintained. Only one chondromyxoid fibroma recurred. Four patients with malignant tumours died from systemic spread of their disease, one is alive with pulmonary metastases and one boy with a unicameral bone cyst was lost during follow-up. Patients with limited surgical procedures had a very good outcome without pain or walking problems. Forefoot or lower limb amputation resulted in significant impairment. All patients except one were able to return to their former profession.

Cytogenetic analysis of a unicameral bone cyst surgically resected in an 11-year-old boy revealed a highly complex clonal structural rearrangement involving chromosomes 4, 6, 8, 16, 21, and both 12. These findings reinforce the need for further studies on unicameral bone cysts to verify the frequency and to understand the significance of chromosome anomalies in this type of lesion.

We report the results of cytogenetic analysis of a case of unicameral bone cyst with a t(16;20(p11.2;q13) present as the sole abnormality. To our knowledge, this is only the second report of a cytogenetically characterized tumor of this type.

RATIONALE AND OBJECTIVES To quantitate features that distinguish the plain radiographic appearance of eosinophilic granuloma (EG) from other solitary lesions of bone. MATERIALS AND METHODS Seven hundred nine focal bone lesions, including 26 EGs, were analyzed according to demographic, anatomic, and plain radiographic features. Vector analysis of groups of features was performed to determine those that are most sensitive and specific for the appearance of EG in contrast to other lesions in the data base. RESULTS The radiographic appearance of EGs was most consistently that of a medullary based lytic lesion (100%) with geographic destruction (76.9%), lobular contour (73.1%), and well-defined edges (73.1%). Long bone lesions showed these features more frequently than EGs in other locations. Periosteal reaction was visible in all long bone lesions but in only one nonlong bone lesion (5.9%). Characterization of EG in long bones as a lytic, medullary-based metaphyseal or diaphyseal lesion with geographic destruction, lobular contours, periosteal reaction, no matrix, and no subarticular extension showed a sensitivity of 55.6% of EG and prevalence of 22.7%. The vector analysis-generated differential diagnoses include unicameral bone cyst, aneurysmal bone cyst, giant cell tumor, Brodie's abscess, enchondroma, chondrosarcoma, and malignant fibrous histiocytoma. CONCLUSIONS The radiographic appearance of EG is relatively nonspecific but, using vector analysis, can be better elucidated than in current textbook descriptions.