Localization of ^99mTc HMDP in an Extraskeletal Myxoid Chondrosarcoma: A Case Report

DISCUSSION

Extraskeletal myxoid chondrosarcoma is an uncommon entity occurring primarily in the deep soft tissue of the extremities. It usually afflicts individuals older than 35 y of age, and males are more frequently affected than females (1). This tumor has the potential to recur and metastasize. The clinical and histologic features of extraskeletal myxoid chondrosarcoma corresponded well with the histology of this case. Bone-imaging agent localization in such a tumor has been reported (2–4). The exact mechanism of bone-imaging agent uptake by extraskeletal myxoid chondrosarcoma is not clear; it may be contributed by hyperemia, calcification, enchondral ossification in the tumors, and reactive new bone formation (2–4). There are 2 hypotheses of the bone agent uptake mechanisms of phosphonate compounds: hydroxyapatite uptake and collagen uptake (5). In the collagen uptake theory, it has been suggested that ^99mTc phosphonate complex localizes in both inorganic and organic matrices of bone, the latter uptake depending on the amount of immature collagen present (5). This is an analogue of the bone scan of a patient with chondrosarcoma in the femur that showed increased uptake (6).

In this case, there was no evidence of calcification or new bone formation on the histologic examination; however, the histopathologic picture of the myxoid chondroid matrix (6), as shown on Figure 2, could explain avid uptake of the bone-imaging agent. In a chondrosarcoma of the femur, increased uptake in the lesion on the bone scintigraphy was demonstrated and chondroid matrix was an essential feature (6). In this patient, myxoid chondroid matrix was the site of bone-imaging agent localization in a chondrosarcoma of the femur.

Despite chemotherapy, extensive metastases developed in the patient’s upper arms, left scapula, lungs, pleurae, and right lower quadrant of the abdomen as evident at autopsy, and he expired within 28 mo. In the article titled, “Microvasculature and vascular endothelial growth factor (VEGF) expression in cartilaginous tumors,” Ayal et al. determined the presence of intracartilage vessels and VEGF expression by malignant chondrocytes (7). Their study demonstrated that angiogenesis is thought to be a vital process of cartilaginous tumors (7), and angiogenesis inhibition is important in the preservation of intact cartilage. Therefore, utilization of angiogenesis inhibition may be explored.