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Presented by Edward McCarthy, M.D. and prepared by Natasha Rekhtman, M.D., Ph.D.
Case 4: A 16-year-old girl had pain in her knee for three months.
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1. Question
Week 199: Case 4
A 16-year-old girl had pain in her knee for three months. A radiograph demonstrated a well-defined lytic lesion in the proximal tibia. This lesion was curetted.images/EMC 4 cb1.jpg
images/EMC 4 cb2.jpg
images/EMC 4 cb4.jpg
images/EMC cb5.jpg
images/EMC cbapptibp.jpgCorrect
Answer: Chondroblastoma
Histology: This lesion is a cellular neoplasm with rounded stromal cells admixed with multinucleated giant cells. There is a faint bluish background in the extra cellular matrix that is an indicator of very early chondroid matrix secretion. The stromal cells are rounded and discohesive, features of chondroblasts. In addition, there is focal calcification of the extra cellular matrix in a “chicken wire” pattern. This indicates chondroblastoma. The radiographic appearance of a well-defined lytic lesion in the epiphyseal end of the long bone is the pattern of chondroblastoma.
Discussion: The lesion is not a giant cell tumor because of the nature of the stromal cells and chondroid matrix. Giant cells tumors do not contain cartilage. In addition, the giant cell tumors, while they involved the epiphyseal end of long bones, usually include the metaphysis. The present lesion is almost entirely confined to the epiphysis.
The lesion is not chondromyxoid fibroma. The chondroid background would be found in a chondromyxoid fibroma. However, the current lesion lacks the spindle cell and myxoid component of a typical chondromyxoid fibroma. In addition, chondromyxoid fibromas involve the metaphyseal portion of the long bone while this lesion involves the epithisis.
Incorrect
Answer: Chondroblastoma
Histology: This lesion is a cellular neoplasm with rounded stromal cells admixed with multinucleated giant cells. There is a faint bluish background in the extra cellular matrix that is an indicator of very early chondroid matrix secretion. The stromal cells are rounded and discohesive, features of chondroblasts. In addition, there is focal calcification of the extra cellular matrix in a “chicken wire” pattern. This indicates chondroblastoma. The radiographic appearance of a well-defined lytic lesion in the epiphyseal end of the long bone is the pattern of chondroblastoma.
Discussion: The lesion is not a giant cell tumor because of the nature of the stromal cells and chondroid matrix. Giant cells tumors do not contain cartilage. In addition, the giant cell tumors, while they involved the epiphyseal end of long bones, usually include the metaphysis. The present lesion is almost entirely confined to the epiphysis.
The lesion is not chondromyxoid fibroma. The chondroid background would be found in a chondromyxoid fibroma. However, the current lesion lacks the spindle cell and myxoid component of a typical chondromyxoid fibroma. In addition, chondromyxoid fibromas involve the metaphyseal portion of the long bone while this lesion involves the epithisis.
