Parosteal Aneurysmal Bone Cyst Mimicking Telangiectatic Osteosarcoma: case report

Posted By Iara Lacerda
Parosteal Aneurysmal Bone Cyst Mimicking Telangiectatic Osteosarcoma: case report

Parosteal aneurysmal bone cyst is a rare subtype of aneurysmal bone cyst. We report a case of a 15 old year girl with a diagnosis of parosteal aneurysmal bone cyst which mimicked telangiectatic osteosarcoma. The radiological and pathological features of both lesions are discussed with a detailed review of the literature. The aim of this report is to raise the awareness of paraosteal aneurysmal bone cyst as differential diagnosis when dealing with an expansile lytic or cystic lesion in the metaphysis of a long bone, with imaging features mimicking a telangiectatic osteosarcoma. It is absolutely important to make the accurate diagnosis since PABC is benign and TOS is malignant and the treatment and prognosis are totally different. As the index case is a good example of these two lesions having significant overlapping features based on imaging, which made tissue examination crucial to render a definitive diagnosis. Case Report: A 15 old year girl was referred to the orthopedic department of our Children’s Hospital with 2 months history of leg pain that was thought to be caused by strained muscles around the right knee. Her leg pain was getting worse despite physical therapy. On physical examination, there was an ill-defined fullness behind the distal portion of the right femur toward the popliteal space. Also noted was tenderness toward the medial posterior side of the right knee. The pulses distal to the knee appeared normal. The groin examination did not reveal any prominent lymph nodes. The skin over this area appeared normal. There was no redness, no dilated vessels and circulation in the toes appeared normal. Laboratory exams were within normal limits, including alkaline phosphatase. AP and lateral radiographs of the extremity showed an aggressive appearing periosteal- based mass along the posteriomedial aspect of the metadiaphysis of distal right femur. The mass has a mildly sclerotic rim and predominantly lucent center with associated aggressive appearing periosteal reaction with lamelled appearance. Incidental note was made of a nonossifying fibroma of the proximal right tibia medially (figure 1-A; 1-B). MRI of the right lower leg with contrast was performed on a 1.5 T MRI system, with a standard extremity coil. Within the distal right femoral metadiaphysis posteromedially, there was a peripheral, periosteal-based, aggressive, relatively well-defined mass measuring 7.3 x 5.3 x 5.4 cm. The mass had predominantly intermediate signal intensity on T1-weighted images and mixed signal intensity on T2-weighted images. This mass contained innumerable internal small cystic spaces with fluid-fluid levels containing material of varying signal intensity. Associated aggressive appearing periosteal reaction along the medial distal femur was noted. The mass enhanced heterogeneously after contrast administration (Figures 2,3,4,5, and 6). A 2.1 cm non-ossifying fibroma was noted within the medial aspect of the right proximal tibia metaphysis No othe

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  • Roland Talanow 2016-08-31 22:39:13

    Thank you for this case. When ABC encountered, one should raise the suspicion for an underlying malignancy. If you wish to submit to the JRCR, what makes it case report worthy? Thank you

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