Antoine Feydy MD, PhD, Presenter: Nothing to Disclose

Mathieu Bui, Abstract Co-Author: Nothing to Disclose

Henri Guerini MD, Abstract Co-Author: Nothing to Disclose

Xavier Poittevin, Abstract Co-Author: Nothing to Disclose

Jean Luc Drapé, Abstract Co-Author: Nothing to Disclose

Alain Chevrot MD, Abstract Co-Author: Nothing to Disclose

Parosteal osteosarcoma is an unusual variant of osteosarcoma. Our purpose was to assess the imaging features of parosteal osteosarcoma.

In our center, 32 adult patients were surgically treated for parosteal osteosarcoma between 1970 and 2004. All had an histologically proven diagnosis of parosteal osteosarcoma (two senior expert musculoskeletal pathologists). Imaging included plain films in all cases (32/32), CT in 9 cases and MRI in 9 cases. All imaging data were retrospectively reviewed by a senior musculoskeletal radiologist. The following features were assessed : tumor topography, size, extension, ossification, tissue component, limits, cortical reaction, presence of a cleft, periosteal reaction, medullar invasion, tissue invasion and articular invasion.

The tumors arised from the femur in 59% (19/32), the tibia (8/32), the humerus (4/32) and the ulna (1/32). The size (large axis) ranged from 2 to 19 cm. Six patients had large tumors with more than 10 cm of greater axis. The underlying bone was totally encircled in only 3 cases. The tumor was well-defined in 63% (20/32). A partial lucent cleft between the tumor and the bone was visible in 72% (23/32). All the tumors were ossified. A tissular component was observed in 59% (19/32) and fatty areas in 2/32. The bone cortex was thickened in 31% (10/32). Only 2 patients had lytic areas of cortical destruction. A periosteal reaction was present in 31% (10/32). Evidence of medullar invasion was present in 3 cases. Extension to the joint was present in 4 cases. A peritumoral tissue invasion was observed in 50% (16/32).

Plain films were most often very suggestive of the diagnosis of parosteal osteosarcoma. CT images were very useful to assess the tumoral extension and the tissular component of the tumors. Most of the cases were typical with well-defined ossified medium-sized (3 to 8 cm) masses arising from the distal femur. Parosteal osteosarcoma may also appear as large ill-defined partially ossified masses with significant tissue component.

Parosteal osteosarcoma is an unusual variant of osteosarcoma. Our purpose was to assess the imaging features of parosteal osteosarcoma.

In our center, 32 adult patients were surgically treated for parosteal osteosarcoma between 1970 and 2004. All had an histologically proven diagnosis of parosteal osteosarcoma (two senior expert musculoskeletal pathologists). Imaging included plain films in all cases (32/32), CT in 9 cases and MRI in 9 cases. All imaging data were retrospectively reviewed by a senior musculoskeletal radiologist. The following features were assessed : tumor topography, size, extension, ossification, tissue component, limits, cortical reaction, presence of a cleft, periosteal reaction, medullar invasion, tissue invasion and articular invasion.

The tumors arised from the femur in 59% (19/32), the tibia (8/32), the humerus (4/32) and the ulna (1/32). The size (large axis) ranged from 2 to 19 cm. Six patients had large tumors with more than 10 cm of greater axis. The underlying bone was totally encircled in only 3 cases. The tumor was well-defined in 63% (20/32). A partial lucent cleft between the tumor and the bone was visible in 72% (23/32). All the tumors were ossified. A tissular component was observed in 59% (19/32) and fatty areas in 2/32. The bone cortex was thickened in 31% (10/32). Only 2 patients had lytic areas of cortical destruction. A periosteal reaction was present in 31% (10/32). Evidence of medullar invasion was present in 3 cases. Extension to the joint was present in 4 cases. A peritumoral tissue invasion was observed in 50% (16/32).

Plain films were most often very suggestive of the diagnosis of parosteal osteosarcoma. CT images were very useful to assess the tumoral extension and the tissular component of the tumors. Most of the cases were typical with well-defined ossified medium-sized (3 to 8 cm) masses arising from the distal femur. Parosteal osteosarcoma may also appear as large ill-defined partially ossified masses with significant tissue component.

Feydy, A, Bui, M, Guerini, H, Poittevin, X, Drapé, J, Chevrot, A, Imaging Features of Parosteal Osteosarcoma.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4414870.html