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Myositis ossificans (MO) is a rare benign cause of heterotopic bone formation in soft tissue that most commonly affects young adults, typically following trauma. We report the case of an 11-year-old girl who developed MO mimicking osteosarcoma in her right shoulder. Plain radiography and computed tomography showed poorly defined flocculated densities in the soft tissue and a periosteal reaction along the proximal humerus. On magnetic resonance imaging, the mass displayed an ill-defined margin and inhomogeneous signal change. Histologically, the mass had a pseudosarcomatous appearance. Based on these findings, the patient was initially misdiagnosed with osteosarcoma at another hospital. The diagnosis was difficult because the patient was 11 years old and had no trauma history, with atypical radiographic changes and a predilection for the site of origin for osteosarcomas. We finally made the correct diagnosis of MO by carefully reviewing and reflecting on the pathological differences between stages., (© 2015 Japan Pediatric Society.)

Soft tissue lesions can contain bone or cartilage matrix as an incidental, often metaplastic, phenomenon or as a diagnostic feature. The latter category includes a diverse group ranging from self-limited proliferations to benign neoplasms to aggressive malignancies. Correlating imaging findings with pathology is mandatory to confirm that a tumor producing bone or cartilage, in fact, originates from soft tissue rather than from the skeleton. The distinction can have dramatic diagnostic and therapeutic implications. This content focuses on the gross, histologic, radiographic, and clinical features of bone or cartilage-producing soft tissue lesions. Recent discoveries regarding tumor-specific genetics are discussed., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Myositis ossificans (MO) may be included in the group of lesions described as pseudosarcomas. Its clinical and histological picture frequently mimics a malignant neoplasm and therefore, ultimate diagnosis and implementation of adequate treatment requires the cooperation of interdisciplinary team of physicians. The paper presents the case of 20-year old female patient suffering from severe pain in the right thigh. The patient was initially diagnosed with the lower limb overload. Rest and administration of non-steroidal anti-inflammatory drugs (NSAID) were recommended. Due to the lack of the efficacy of the recommended conservative treatment and detection of tumorous mass on ultrasound examination, the patient was referred to the cancer centre. The diagnostic procedures were extended and an open biopsy of the lesion was performed which revealed the presence of MO. The patient underwent a surgical procedure during which the pathological mass was entirely removed. Follow up examinations conducted upon the conclusion of the rehabilitation indicate no pathologies in the operated area.

This article discusses the most common diagnostic dilemmas when trying to distinguish between tumor and sports injury or other trauma. Bone tumors frequently occur in the same young active patients who experience sports injuries. If the pain persists longer than expected, imaging studies should be obtained to prevent a delay in diagnosis or an inappropriate arthroscopy. A history of spontaneous fracture or a fracture after minor trauma should raise suspicion for underlying lesion as the cause. Occasionally necrosis and/or hemorrhage within a soft tissue sarcoma is so extensive that only a small cuff of viable tumor tissue is present., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Reactive lesions of bone and soft tissue can appear alarming on histologic examination because they are often cellular and have atypical (activated) cytologic features, such as distinct nucleoli and mild hyperchromasia, and mitotic activity. Reactive lesions of bone and periosteum also produce bone and cartilage matrix, resulting in confusion with osteosarcoma or chondrosarcoma. Careful attention to key cytomorphological features such as the pattern of bone formation, uniform appearance of cells, and absence of atypical mitoses should help identify the reactive nature of a lesion. Correlation with clinical and radiological findings is also imperative to avoid misclassification of the tumor because reactive lesions often arise at sites where osteosarcoma and chondrosarcoma are rare (e.g., the hand) and lack aggressive radiological features. In this review we discuss reactive lesions of bone that are commonly confused with malignant neoplasms and that the practicing pathologist is likely to encounter at some point. Several of these lesions have had characteristic chromosomal translocations documented in recent years, but continue to be included as reactive lesions based on their overall clinicopathological features.

Whether discovered incidentally or as part of a focused diagnostic evaluation, the finding of a benign osseous lesion that has radiologic features resembling a bone tumor is not uncommon. Some of the more common benign and nonneoplastic entities that can sometimes be confused with tumors are the following: cortical desmoid, Brodie abscess, synovial herniation pit, pseudocyst, enostosis, intraosseous ganglion cyst, fibrous dysplasia, stress fracture, avulsion fracture (healing stage), bone infarct, myositis ossificans, brown tumor, and subchondral cyst. Accurate diagnosis and management of these lesions require a basic understanding of their epidemiology, clinical presentations, anatomic distributions, imaging features, differential considerations, and therapeutic options. This in-depth review of 13 potential bone tumor mimics will assist the radiologist in correctly identifying these benign lesions and in avoiding misdiagnosis and related morbidity. This review will also aid the radiologist in making appropriate recommendations to the referring physician for management or further imaging.

The aim of the study is presentation of problems in osteosarcoma diagnosis. In 3 cases possibilities of mistakes especially in differential diagnosis with myositis ossificans are presented.

Musculoskeletal neoplasms are rare, and both the medical history and complaints of the patients are usually uncharacteristic and of limited information. After a clinical evaluation and biplane conventional radiography, the clinician must classify the patient as having a nonprogressive or progressive primary benign, primary malignant, or metastatic bone tumor. In the case of a probably benign, nonprogressive bone tumor, the patient has to be observed continuously or an additional biopsy should be performed. In the case of a probably malignant lesion, the patient should be referred for further staging and treatment to an orthopedic oncologist. Conventional biplane radiography, scintiscan, computed tomography scan, and magnetic resonance imaging (MRI) are indispensable in staging and treatment planning for patients with musculoskeletal tumors. For limb salvage procedures, delineation of the tumor from adjacent tissue structures is crucial. Hence, MRI of the entire anatomic structure involved, together with adjacent joints, is of the utmost importance, both in the coronal and axial planes. The significance of MRI in clinical follow-up depends on keeping the sequences and imaging planes used constant. Differentiating pseudotumors from true neoplasms still poses a challenge. The cellular pattern and matrix characteristics of a lesion cannot definitely be identified as neoplastic even with application of all imaging modalities including MRI. Information on epidemiology, clinical picture, radiology, and histology of the lesion is necessary to draw a firm conclusion. Biopsy is still the first choice in making the diagnosis.

The purpose of this report is the study of a malignant bone tumor of similar histological picture with conventional (intramedullary) osteosarcoma. Contributing factors in the study of juxtacortical osteosarcoma are the clinical, X-ray and histologic pictures. A case of parosteal osteosarcoma in a 28-year-old male is reported. In conjuction with X-ray findings we review the histological characteristics of the tumor through serial sections of the peripheral, central and parosteal parts and the findings are described in detail. In addition to the histological findings, differential diagnosis and prognosis are also discussed. From the general study of the tumor it has been shown that juxtacortical osteogenic sarcoma behaves differently in contrast to classic osteosarcoma, depending on the degree of differentiation of the tumor.

Objective: To discuss the clinical radiographic findings in a 70-yr-old woman suffering from chondrosarcoma., Clinical Features: The patient experienced right SI pain present initially only at night. She later developed morning numbness. An X-ray examination revealed a flocculent calcification in the right buttock region. Computed tomographic scans confirmed the diagnosis., Intervention and Outcome: Initial palliative care continued until surgery was performed to resect the area., Conclusion: Chondrosarcoma is a severe disease that must be differentiated from myositis ossificans.

MRI has gained an undisputed place in the evaluation of malignant bone tumors, not only for verifying results of conventional radiographs and clarifying differential diagnoses; it has also become increasingly important for the assessment of the malignant/benign nature of the tumor, its growth rate, definition of adequate sites for biopsy, local preoperative staging, and evaluation of the response to chemotherapy. However, several pitfalls have to be observed regarding choice of technical parameters (coils, sequences, imaging planes), tissue differentiation, and tumor staging. When staging malignant tumors, critical aspects which have to be observed are tumor extension, integrity of the cortical bone, soft tissue components, infiltration of a joint or neurovascular bundle. The use of contrast agents provides important additional information but can also give rise to misinterpretations. Thus, all features of a tumor have to be observed in order to establish a final diagnosis. Particular difficulties can occur with the interpretation of MR images of osteomyelitis, osteoid osteoma, stress and insufficiency fractures, bone infarcts, myositis ossificans, hemangiomas, and aneurysmal bone cysts.

The object of this presentation is to discuss the characteristics of a few primary bone tumors (osteochondroma versus chondrosarcoma), as presented in the literature, in relation to a specific lesion that the authors encountered. The specific lesion, an unusual osteochondroma arising from the plantar aspect of the first metatarsal, had a few characteristics of its own that are presented. This case report includes the pertinent history and clinical findings of the lesion with associated radiographic laboratory and pathology results that are very essential in determining an accurate differential diagnosis. The surgical discussion and postoperative care is important in discussing the particular characteristics of this tumor and the pattern of its regrowth. Recurrence of a lesion of this type is very rare and, when it does occur, must undergo much scrutiny. This regrowth is the most perplexing characteristic of this tumor and the reason for the lengthy presentation. The final diagnosis remained osteochondroma with benign postoperative ectopic bone formation. It is the authors' opinion that this is a very atypical lesion in the study of bone tumors and is a worthwhile presentation to the literature as such.

This study is based on 41 cases of parostesl (or juxta cortical) osteogenic sarcoma, which the authors prefer to define as periosteal osteosarcoma. The clinical features, radiological and histological characteristics are analysed. Treatment and prognosis are discussed. The treatment usually indicated is amputation, but in selected cases radical segmental resection is appropriate. The prognosis is comparatively favourable if the correct surgical treatment is carried out without delay.

Juxtacortical osteosarcoma should be considered a very rate distinctive entity under all malignant bone tumors. The tumor has a remarkable tendency to grow from the periostal tissues peripherally with a usually marked degree of ossification without primary medullary involvement. It's different und characteristic behavior in clinical, roentgenographic and microscopic findings from that of other types of bone-forming sarkomas is discussed by means of a just treated case. In contrast to osteogenic osteosarcoma the prognosis for early well treated juxtacortical osteosarcoma is much better.