A case of parosteal osteosarcoma with a rare complication of myositis ossificans

Dedifferentiated Osteosarcoma of the Distal Ulna: A Case Report

Osteosarcoma is the most common malignant primary bone tumor that occurs most frequently in the second decade of life but rarely in patients over 40 years of age. The most common primary sites of osteosarcoma are the distal femur followed by proximal tibia and proximal humerus, and involvement of the wrist is extremely rare. Moreover, dedifferentiated osteosarcoma is also a rare condition that progresses to high-grade osteosarcoma from low-grade osteosarcoma, usually central low-grade osteosarcoma or parosteal osteosarcoma that bears MDM2 and/or CDK4 gene amplifications. We herein report an extremely rare case of dedifferentiated osteosarcoma arising in the distal ulna of an adult over 40 years of age. The patient was a 46-year-old man with a 2-month history of pain in his left swollen wrist. The initial radiological findings suggested a benign bone tumor in the distal ulna, and the lesion was marginally excised at the nearby hospital. Although the pathological diagnosis at the nearby hospital suggested a benign cartilaginous tumor, the tumor recurred in an aggressive manner 8 months after the initial surgery. The patient was referred to our hospital, and an incisional biopsy showed a high-grade osteosarcoma. The primary tumor was retrospectively re-evaluated at our hospital and diagnosed as low-grade osteosarcoma. Since neoadjuvant chemotherapy failed to shrink the tumor, the patient had to undergo below the elbow amputation to cure the disease. Although the tumor was negative for MDM2 nor CDK4, the definitive diagnosis of dedifferentiated osteosarcoma was made according to the clinical course and the histological findings. Lung metastases were found 10 months after the amputation, which were successfully treated by neoadjuvant chemotherapy and surgery. The patient has been doing well with no evidence of disease for 1 year and 6 months. Surprisingly, the literature review revealed that many low-grade osteosarcomas of the distal ulna progressed to high-grade dedifferentiated osteosarcomas. One should bear in mind that the diagnosis and treatment for bone-forming tumors of the distal ulna should be made very carefully because, although rare, it is possible that the tumor may initially appear as a benign or low-grade malignant tumor and may progress to high-grade osteosarcoma.

Bifocal parosteal osteoma of femur: A case report and review of literature

Osteoma is a benign, slowly growing, asymptomatic, bone-forming tumor arising from cancellous or compact bone. Osteoma usually is a solitary lesion, but in patients with Gardner’s Syndrome it may be multiple. osteoma may rarely have a parosteal localization. Parosteal osteoma has peculiar radiographic, histologic and clinical features. We describe a case report of a 51- years old man with a bifocal parosteal osteoma of the femur in a non-syndromic patient. This is the first described patient with a bifocal lesion. In literature only 24 cases of paraosteal osteoma are found. Our patient underwent surgery and the lesions were fully excised. At one year follow-up there was no evidence of recurrence.

Value of 99mTc-MDP SPECT/CT and 18F-FDG PET/CT scanning in the evaluation of malignantly transformed fibrous dysplasia

Although fibrous dysplasia is not considered a potentially premalignant disorder, malignant transformation occurs. Because of its rarity, radiographic features of malignantly transformed fibrous dysplasia on cross-sectional imaging modalities are less recognized, making diagnosis and differential diagnosis of the disease quite difficult in clinical practice. In this study, we analyzed the clinical characteristics, imaging features, pathology findings and surgery strategies of 19 malignantly transformed fibrous dysplasia. We found that there was significant male predominance in this specific cohort (13/6). While osteosarcoma (63.2%) was the most frequently occurring neoplasm secondary to fibrous dysplasia, other less commonly malignantly changed types included fasciculated sarcoma, malignant fibrous histiocytoma, fibrosarcoma and chondrosarcoma. We found that the diagnostic value of single modality imaging method, like conventional X-ray, computed tomography or non-contrast magnetic resonance imaging, was limited mainly because of a lack of whole-body metabolic information. In contrast, we highlighted that ^99mTc-MDP SPECT/CT and/or ¹⁸F-FDG PET/CT scanning could exert a pivotal role in the management of malignantly transformed fibrous dysplasia by guiding precise biopsy and optimizing surgery options.