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Presented by Edward McCarthy, M.D. and prepared by Natasha Rekhtman, M.D., Ph.D.
Case 4: A 20-year-old man had a lump in his arm which was increasing in firmness.
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1. Question
Week 229: Case 4
A 20-year-old man had a lump in his arm which was increasing in firmness over the past several months. A radiograph demonstrated a well defined radiodensity in the area of his biceps muscle.images/EMC 06 2005 case 4 1.jpg
images/EMC 06 2005 case 4 2.jpg
images/EMC 06 2005 case 4 3.jpg
images/EMC 06 2005 case 4 4.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 stroma 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 stroma 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.
