Low-grade parosteal osteosaracoma of the ulna with dedifferentiation into high-grade osteosarcoma

Histological background of dedifferentiated solitary fibrous tumour

AIMS

Dedifferentiation is a histological phenomenon characterised by abrupt transition of histology to a sarcomatous component with high-grade malignant potential in solitary fibrous tumour (SFT). The authors histologically reviewed SFT cases to reveal the histological background of dedifferentiated SFTs.

METHODS

Clinicopathological and histopathological findings of 145 SFT cases were reviewed. Immunohistochemical staining and genetic analysis were also performed.

RESULTS

The non-dedifferentiated components showed a cellular component in 45 of 145 (31%), high mitotic rate (≥4/10 high-powered field) in 12 of 145 (8.2%) tumours, necrosis in 7 of 145 (4.8%) tumours, multinodular growth pattern in 39 of 132 (29.5%) available tumours and intratumoural fibrous septa in 37 of 131 (28.2%). Immunohistochemically, the non-dedifferentiated components were positive for CD34 in 128 of 141 (90.7%), bcl-2 in 101 of 133 (75.9%), nuclear pattern of β-catenin in 64 of 127 (50.3%) and p16 in 22 of 140 (15.7%). Loss of Rb protein expression was detected in 17 of 110 (15.4%) cases. Statistically, cellular component, multinodular structure, p16 overexpression and Rb protein loss were significantly associated with dedifferentiation. Moreover, cellular component and multinodular structure were significantly associated with p16 overexpression and Rb protein loss. All the non-deddifferentiated components showed wild type of p53 expression. The dedifferentiated components of all 10 dedifferentiated tumours presented positivity for p16 in 9 of 10 (90%) and mutational type of p53 in 5 of 10 (50%). Loss of Rb protein expression was detected in 6 of 10 (60%).

CONCLUSIONS

The authors propose that cellular or multinodular transformation may be associated with dedifferentiation. They also suggest that cellular and multinodular transformation may be associated with p16 overexpression and Rb downregulation.

Custom-made intercalary endoprosthetic reconstruction for a parosteal osteosarcoma of the femoral diaphysis: A case report

The present report describes a case of a 44-year-old female patient who presented with a palpable mass of the left thigh. A diagnosis of parosteal osteosarcoma (POS) at the femoral diaphysis was made following a diagnostic workup. Previous reports of long bone diaphyseal POS are rare. A long diaphyseal segment of the femur containing the tumor was resected along with a healthy margin of soft tissues, and the damaged bone was reconstructed with a custom-made intercalary endoprosthesis. Subsequent pathological examination of the surgical sample confirmed the diagnosis of POS. No local recurrence or distant metastasis was observed, and the patient had a positive Musculoskeletal Tumor Society score of 28/30 (93.3%) at the 28-month post-surgery follow-up. The present study describes the clinical, radiological, and pathological features of this rare type of osteosarcoma.

Surface primary bone tumors: Systematic approach and differential diagnosis

Surface primary bone tumors may appear similar to their intramedullary counterpart, but because they are rare, they may pose diagnostic challenges when showing different characteristics compared to their intramedullary counterpart. It is important for radiologists to recognize the imaging findings for various uncommon surface primary bone tumors, which may help to reduce the differential diagnosis or to lead to a specific diagnosis. Radiography is typically used for first-line imaging. If necessary, it is followed by CT or MRI for evaluation and characterization of surface bone tumors. The aim of this article is to review the imaging findings and differential diagnosis for surface primary bone tumors.

Dedifferentiated parosteal osteosarcoma with giant cell tumor component

Dedifferentiated parosteal osteosarcoma is characterized histologically by the admixture of low-grade fibroblastic osteosarcoma and a high-grade component typically resembling conventional osteosarcoma or malignant fibrous histiocytoma. We report an unusual distal femoral dedifferentiated parosteal osteosarcoma in which the dedifferentiated component resembled a giant cell tumor of bone. This phenotype is rarely described in the dedifferentiated component of a dedifferentiated parosteal osteosarcoma. The clinical, radiographic, and pathologic features of this unusual tumor are described to further expand the histologic spectrum of dedifferentiated parosteal osteosarcoma.

Osteossarcoma parosteal: aspectos na radiologia convencional

OBJETIVO: Avaliar os achados clínicos mais importantes do osteossarcoma parosteal e descrever os seus aspectos mais comuns na radiologia convencional. MATERIAIS E MÉTODOS: Estudo retrospectivo com 26 pacientes com osteossarcoma parosteal, provenientes do arquivo do Clube do Osso, Rio de Janeiro, RJ, e análise dos principais achados clínicos e aspectos radiológicos. RESULTADOS: A doença predominou em pacientes do sexo feminino e teve idade média de acometimento na terceira década de vida. Os achados clínicos mais freqüentes foram o aumento do volume no local do tumor (77% dos casos) e a dor local (68% dos casos). O local mais comum de tumor foi o oco poplíteo, com 40% dos casos, e houve envolvimento metafisário em 92% dos tumores. O aspecto radiológico mais comumente encontrado foi de lesão bem mineralizada e intimamente justaposta à superfície óssea, com o córtex adjacente irregularmente espessado (92,3% dos casos), observando-se área de adesão a este (88,5% dos casos), além de margens tumorais lobuladas (50% dos casos) ou irregulares (38,5% dos casos). Evidenciaram-se, também, linha radiolucente entre o tumor e o osso adjacente (48% dos casos), padrão de mineralização mais denso na base do que na periferia (42,3% dos casos) e pequena ocorrência de reação periosteal (15,4% dos casos). CONCLUSÃO: Apesar de a tomografia computadorizada e a ressonância magnética serem importantes na identificação de alguns aspectos do osteossarcoma parosteal, a radiologia convencional é altamente sugestiva deste tumor e permite, na maior parte dos casos, o diagnóstico diferencial com outras lesões da superfície óssea.

Parosteal osteosarcoma of the distal ulna. A rare tumour at a rare location: a case report

We report a case of a histologically well differentiated, grade I, parosteal osteosarcoma of the distal ulna. The tumour's radiological and histological features are described, and the patient's course after wide en-bloc resection is detailed. Parosteal osteosarcoma is a rare low-grade malignant neoplasm. It belongs to the group of the osteosarcomas originating from the surface of the bone, representing a distinct tumour entity within this group, with defined histological and radiological features. We describe the radiological and histological characteristics of parosteal osteosarcoma and, based upon these features, present its classification. The differential diagnosis, including parosteal osteoma, myositis ossificans and osteochondroma, is also discussed. Finally, therapy and prognosis are outlined in accordance with the current literature. Wide en-bloc resection represents the mainstay of therapy offering an excellent prognosis with a 5-year survival rate of more than 90%. Incomplete resection, on the other hand, increases the risk of recurrence and dedifferentiation of the tumour. Dedifferentiation induces tumour spread and is associated with a poor prognosis equivalent to conventional osteosarcoma.

Parosteal osteosarcoma with myocardial metastasis 13 years after follow-up

PURPOSE

To report the case of a woman with a diagnosis of grade II (low grade) parosteal osteosarcoma with the occurrence of myocardial metastasis 13 years after resection, and to present a review of the existing literature on the subject.

METHODS

Description of the case and review of the literature.

CONCLUSION

The review leads to the conclusion that the occurrence of metastasis from parosteal osteosarcoma can occur in up to 38% of the cases, in spite of its relatively low aggressiveness. However, myocardial metastasis of a parosteal osteosarcoma is an event that was not found in the literature.

The role of imaging modalities in the diagnosis of primary dedifferentiated parosteal osteosarcoma

Dedifferentiated parosteal osteosarcoma (dd-POS) is defined as high-grade sarcomatous components coexisting with low-grade POS components. With regard to the histological diagnosis of dd-POS, the sampling of a small area of dedifferentiation through the densely mineralized POS can be a problem. In this situation, imaging is important to identify the area with the highest possibility of dedifferentiation. We report a patient in whom dedifferentiation was shown by computed tomography (CT) and magnetic resonance imaging (MRI). CT revealed a radiolucency in a highly mineralized area. T2-Weighted MRI showed a relatively high signal intensity, corresponding to the radiolucency, surrounded by a very low signal intensity area. Furthermore, gadolinium-enhanced T1-weighted MRI showed marked enhancement. Based on these imaging techniques, the condition was diagnosed as most likely to be a dd-POS, although a representative sample was not accessible by incisional biopsy. Neoadjuvant chemotherapy was administered, followed by wide resection and adjuvant chemotherapy. Four years after the surgery, partial lobulectomy was required because of a pulmonary metastasis. Three years after the second surgery, the patient remained well without evidence of metastases. Based on the initial diagnosis and, consequently, the optimal treatment of combined chemotherapy and wide resection, our patient showed a good clinical outcome.