Hemicortical Resection and Biological Reconstruction using Allograft for Parosteal Osteosarcoma of the Distal Femur. A Case Series

Background: Parosteal osteosarcoma (PAO), which is a surface osteosarcoma, can be treated with wide excision and endoprosthetic or allograft application. However, due to the low local recurrence and metastasis rate, when it appears in the posterior surface of the distal femur, can be managed with hemicortical wide resection and biological reconstruction with hemicortical allograft.The purpose of this study was to evaluate the oncological and functional outcomes of patients with parosteal osteosarcoma (PAO) of the posterior cortex of the distal femur who underwent biological reconstruction after hemicortical resection. Methods: Eleven patients who underwent wide tumor resection and defect reconstruction of the posterior surface of the distal femur using hemicortical allograft were studied retrospectively. Local recurrence, metastasis, complications and the functional outcome using the Musculoskeletal Tumor Society scoring system (MSTS Score) were evaluated.Results: The average postoperative follow-up period was 53.64 months (range, 30 to 84 months). At the latest follow up, all patients were free of the disease without appearing any metastases. A patient with local recurrence underwent revision surgery with fibula autograft reconstruction. The mean MSTS score was 93.45 ± 3.56. Conclusions: In patients with PAO of the posterior aspect of the distal femur the treatment of hemicortical resection and allograft reconstruction has satisfactory oncological and functional outcomes and low complication rates.

Allograft reconstruction for large parosteal osteoma of the clavicle: a case report

A large parosteal osteoma arising on the surface of the right clavicle of a 39-year-old male patient was suspected preoperatively as a parosteal osteosarcoma. The lesion was treated with wide resection and allograft reconstruction. In this case report, we discuss the accurate diagnosis and appropriate surgical treatment for unusual clavicular tumors.

Case Report: Metastatic Parosteal Osteosarcoma in a Dog

This case report describes a rare form of malignant bone tumor in an 8-year-old Labrador retriever. This dog initially presented for evaluation of a right distal humeral mass. Radiographs of the right elbow and thorax were performed, revealing a smooth mineralized mass adjacent to the lateral aspect of the distal humerus and a 5mm pulmonary nodule. Computed tomography (CT) of the humerus and thorax showed a smooth mineralized lesion adjacent to the lateral humeral epicondyle, and a right cranial lung lobe nodule with a thin mineral rim. Surgical biopsies of both lesions were diagnostic for parosteal osteosarcoma (POSA). The dog was then treated with stereotactic body radiation therapy (SBRT) which controlled the dog's discomfort for 14 months until he became progressively painful and subsequently had his right forelimb amputated. This case report is the first to document the CT imaging characteristics of a metastatic appendicular POSA in a dog and the first dog described with POSA treated with SBRT. The dog lived for 623 days after histopathologic diagnosis and 849 days after initial presentation with pulmonary metastatic disease.

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.

Parosteal Osteosarcoma with Pancreatic Metastasis and Multiple Relapses: A Case Report and Review of the Literature

Osteosarcoma is the most common primary bone cancer in all age groups. Metastasis mostly occurs with high-grade tumors disseminating to the lungs and other bones. Spread to the pancreas is rare and undocumented in the low-grade subtypes. Additionally, it is uncommon for the disease course of low-grade subtypes to involve multiple relapses. We present a 35-year-old woman with parosteal osteosarcoma who has experienced an atypical metastasis to the pancreas as well as multiple local and pulmonary relapses. The lesion was identified incidentally on routine imaging, and the patient underwent resection. We compare our case to the other reports of pancreatic metastasis in the literature. Despite being especially rare, clinicians ought to be aware of pancreatic metastasis of osteosarcoma. Furthermore, despite parosteal osteosarcoma’s less aggressive disease course, it can uncommonly lead to multiple relapses. We present a rare case exemplifying these phenomena in the prognostically favorable histologic subtype of parosteal osteosarcoma.