Musculoskeletal and Skin Pathology for Medical II Students

Lab 1e Osteosarcoma (11000-91803)

Osteosarcoma (osteogenic sarcoma) is the most common primary malignant tumor of bone. It is a neoplasm of mesenchymal cells in which the tumor cells produce osteoid or bone. Most osteosarcomas are primary (no underlying bone disease) and arise in the second decade of life. The most common sites for primary osteogenic sarcoma are in the lower end of the femur and the upper end of the tibia (around the knee joint). Secondary osteosarcoma develops in a patient with a preexisting bone disease, most often Paget's disease of bone, multiple osteochondromas, enchondromas or after irradiation. The slide in your class set is from a conventional or medullary osteogenic sarcoma. There exist other variants of osteosarcoma, such as parosteal osteosarcoma, that have a different histologic appearance and prognosis. As with all bony lesions, it is essential to correlate the gross and histopathologic features with the history and physical findings, and radiographic appearance.

Slides 8 & 9 | Slides 10 & 11

Slide 10 Histologically, the two most important features of osteogenic sarcoma are malignant stroma and malignant osteoblasts associated with osteoid and bone. This latter feature is often termed "malignant osteoid". This low power slide shows a background of malignant stroma, with malignant cells with osteoid.
Slide 11 The malignant stroma often is undifferentiated, with highly pleomorphic tumor cells.

Digital Legends for Labs/Cases
Lab 1
1a | 1b | 1c | 1d | 1e | 1f | 1g
Gross & Radiographs
a | b | c | d | e | f | g | h 
Lab 2
2a | 2b | 2c | 2d | 2e | 2f

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Medical II

Updated August 28, 2007