Undifferentiated Pleomorphic Sarcomas

Classification and Terminology

The current classification orders spindle cell sarcomas of the bone as part of the diagnostically heterogeneous group of malignant tumors referred to as undifferentiated pleomorphic sarcomas, according to the British Journal of Cancer and Annals of Oncology 1, 2
The terminology has changed over time: what was previously referred to as malignant fibrous histiocytoma (MFH) or fibrosarcoma is now encompassed under the term "undifferentiated pleomorphic sarcoma", as stated by Annals of Oncology 3, 4
This group includes various pleomorphic high-grade sarcomas without a specific line of differentiation, as noted by British Journal of Cancer and Annals of Oncology 1, 2

Undifferentiated pleomorphic sarcomas, including spindle cell sarcomas, account for approximately 2-5% of all primary bone malignancies, according to Annals of Oncology 3, 4
They typically occur in a similar age group to chondrosarcomas, but their skeletal distribution is more similar to osteosarcoma, as reported by Annals of Oncology 2, 5
Clinical presentation typically includes pain and a high incidence of pathological fractures at initial presentation, as noted by Annals of Oncology 3, 6
They more frequently affect men than women, according to Annals of Oncology 4, 5

It is not uncommon for a spindle cell sarcoma to be identified as a dedifferentiated chondrosarcoma or osteosarcoma after further histological examination, as stated by Annals of Oncology 3, 2
Diagnosis requires complete staging and biopsy, as recommended by Annals of Oncology 4, 6

Treatment strategies are similar to those for osteosarcoma, including chemotherapy and complete en-bloc resection, as noted by Annals of Oncology 3, 4
Undifferentiated pleomorphic sarcomas are typically high-grade with metastasis rates of at least 50%, according to British Journal of Cancer 1
The sensitivity to chemotherapy is less well-known than for other bone sarcomas, as reported by Annals of Oncology 2, 6