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Presented by Edward McCarthy, M.D. and prepared by Dengfeng Cao, M.D. Ph.D.
Case 1: A 20 year old man had a lump in his thigh which was increasing in firmness over the past several months.
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Question 1 of 1
1. Question
Week 196: Case 1
A 20 year old man had a lump in his thigh which was increasing in firmness over the past several months. A radiograph demonstrated a well defined radiodensity in the area of his quadraceps muscle.images/Cao_100604case1a.jpg
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images/Cao_100604case1e.jpgCorrect
Answer: Heterotopic ossification
Histology: The radiograph shows a well defined radiodense mass. The trabecular pattern of the radiodensity indicates that the lesion is composed of bone. Histologically, there is osteoid deposition in a cellular fibrous tissue stroma. There is a distinct zonal pattern i.e. the bone is more dense at the periphery of the lesion. The central cellular area shows a distinct “tissue culture-like”appearance. Although the stromal is cellular, there is no evidence of pleomorphism or atypical mitotic figures.
Discussion: The lesion is not an osteogenic sarcoma because of the lack of atypia and abnormal mitotic figures. In addition, the zonal pattern is an indicative of a non-neoplastic, reactive disorder. Zonal patterns are not present in osteogenic sarcoma.
The lesion is not a chondrosarcoma. Although the radiograph may raise the possibility of a cartilage tumor, there is no cartilage in the lesion.
The lesion is not tumoral calcinosis because there is not evidence of a dystrophic calcification. In this case, the radiodensity is entirely due to bone formation.
Incorrect
Answer: Heterotopic ossification
Histology: The radiograph shows a well defined radiodense mass. The trabecular pattern of the radiodensity indicates that the lesion is composed of bone. Histologically, there is osteoid deposition in a cellular fibrous tissue stroma. There is a distinct zonal pattern i.e. the bone is more dense at the periphery of the lesion. The central cellular area shows a distinct “tissue culture-like”appearance. Although the stromal is cellular, there is no evidence of pleomorphism or atypical mitotic figures.
Discussion: The lesion is not an osteogenic sarcoma because of the lack of atypia and abnormal mitotic figures. In addition, the zonal pattern is an indicative of a non-neoplastic, reactive disorder. Zonal patterns are not present in osteogenic sarcoma.
The lesion is not a chondrosarcoma. Although the radiograph may raise the possibility of a cartilage tumor, there is no cartilage in the lesion.
The lesion is not tumoral calcinosis because there is not evidence of a dystrophic calcification. In this case, the radiodensity is entirely due to bone formation.
