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Presented by Edward McCarthy, M.D. and prepared by Julie M. Wu, M.D.
Case 1: A 65 year-old man had pain in his groin.
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Question 1 of 1
1. Question
Week 330: Case 1
A 65 year-old man had pain in his groin. A plain radiograph demonstrated a permeative lytic lesion in his pubis.images/jmw110507/1.1.jpg
images/jmw110507/1.2.jpg
images/jmw110507/1.3.jpgCorrect
Answer: Malignant fibrous histiocytoma
Histology: Malignant fibrous histiocytoma of bone the most common primary bone sarcoma in older adults after chondrosarcoma. This lesion shows a population of pleomorphic spindle cells admixed with pleomorphic round cells. There is abundant hyalinized collagen admixed with the tumor cells. The mitotic rate is very high. This pattern of cells in a storiform pattern is diagnostic of malignant fibrous histiocytoma.
Discussion: Although osteosarcomas occur in older patients, there is usually a history of prior radiation or Paget’s disease in that area. The dense hyalinizing collagen present in this case is not osteoid. The only positive way to identify osteoid and distinguish it from regular collagen is whether it mineralizes. Osteoid has non-collagenous proteins which allow it to be mineralized. There is no evidence of mineralization of this pink collagen in this case. Therefore it is not osteoid.
Metastatic carcinoma in bone is the most common malignant bone tumor in older individuals. This diagnosis must be first on the list when considering an older patient with a lytic bone tumor. However, an organoid pattern of epithelial cell is not present in this slide. The remote possibility of a metastatic sarcomatoid renal cell carcinoma should be considered. Therefore, a keratin stain or a stain for epithelial membrane antigen (EMA) should be performed. In addition, the patient should have a CT of his abdomen to rule out a renal mass.
Incorrect
Answer: Malignant fibrous histiocytoma
Histology: Malignant fibrous histiocytoma of bone the most common primary bone sarcoma in older adults after chondrosarcoma. This lesion shows a population of pleomorphic spindle cells admixed with pleomorphic round cells. There is abundant hyalinized collagen admixed with the tumor cells. The mitotic rate is very high. This pattern of cells in a storiform pattern is diagnostic of malignant fibrous histiocytoma.
Discussion: Although osteosarcomas occur in older patients, there is usually a history of prior radiation or Paget’s disease in that area. The dense hyalinizing collagen present in this case is not osteoid. The only positive way to identify osteoid and distinguish it from regular collagen is whether it mineralizes. Osteoid has non-collagenous proteins which allow it to be mineralized. There is no evidence of mineralization of this pink collagen in this case. Therefore it is not osteoid.
Metastatic carcinoma in bone is the most common malignant bone tumor in older individuals. This diagnosis must be first on the list when considering an older patient with a lytic bone tumor. However, an organoid pattern of epithelial cell is not present in this slide. The remote possibility of a metastatic sarcomatoid renal cell carcinoma should be considered. Therefore, a keratin stain or a stain for epithelial membrane antigen (EMA) should be performed. In addition, the patient should have a CT of his abdomen to rule out a renal mass.
