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Presented by Edward McCarthy, M.D. and prepared by Maryam Farinola M.D.
Case 2: A 14 year old boy had pain in his knee for 8 months.
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Question 1 of 1
1. Question
Week 214: Case 2
A 14 year old boy had pain in his knee for 8 months. A radiograph demonstrated a well circumscribed lytic lesion in the distal femoral metaphysis. The lesion was multilobular with a sclerotic rim. The lesion was biopsied.images/nonossifying fibroma 1.jpg
images/nonossifying fibroma 2.jpg
images/nonossifying fibroma 3.jpgCorrect
Answer: Non-ossifying fibroma
Histology: A non-ossifying fibroma is a lesion which is found exclusively in the metaphyseal zones of long bones. The distial tibia, as in this case, is a common location. Histologically, non-ossifying fibromas have a spindle cell proliferation of cells in a storiform pattern. Occasionally, as in this case, many multinucleated giant cells are present. The stromal shows no evidence of cytologic atypia.
Discussion: The lesion is not a giant cell tumor because this lesion is confined to the metaphysis. By contrast, giant cell tumors when involving long bones involve both the epiphyseal and metaphyseal zones. Although this lesion has many multinucleated giant cells, the stroma lacks the typical stromal cells of the giant cell tumor. Giant cell tumor stromal cells are round or polygonal whereas in the present case, the stromal cells are spindle shaped.
This lesion is not an aneurysmal bone cyst. The typical blood-filled lakes with thin septal walls are not present histologically. Aneurysmal bone cyst is a lesion which maybe engrafted on other lesions such as non-ossifying fibroma. However, the changes of aneurysmal bone cyst are not present in this case.
The lesion is not a malignant fibrous histiocytoma because, despite the storiform pattern, there is no pleomorphic stroma or abnormal mitotic figures.
Incorrect
Answer: Non-ossifying fibroma
Histology: A non-ossifying fibroma is a lesion which is found exclusively in the metaphyseal zones of long bones. The distial tibia, as in this case, is a common location. Histologically, non-ossifying fibromas have a spindle cell proliferation of cells in a storiform pattern. Occasionally, as in this case, many multinucleated giant cells are present. The stromal shows no evidence of cytologic atypia.
Discussion: The lesion is not a giant cell tumor because this lesion is confined to the metaphysis. By contrast, giant cell tumors when involving long bones involve both the epiphyseal and metaphyseal zones. Although this lesion has many multinucleated giant cells, the stroma lacks the typical stromal cells of the giant cell tumor. Giant cell tumor stromal cells are round or polygonal whereas in the present case, the stromal cells are spindle shaped.
This lesion is not an aneurysmal bone cyst. The typical blood-filled lakes with thin septal walls are not present histologically. Aneurysmal bone cyst is a lesion which maybe engrafted on other lesions such as non-ossifying fibroma. However, the changes of aneurysmal bone cyst are not present in this case.
The lesion is not a malignant fibrous histiocytoma because, despite the storiform pattern, there is no pleomorphic stroma or abnormal mitotic figures.
