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Dedifferentiated chordoma is a rare form of chordoma in which part of the tumour has turned into a high-grade sarcoma, usually after recurrence or radiotherapy but sometimes from the start. The sarcoma component decides the outcome, which is much worse than ordinary chordoma, so it is treated with surgery and the chemotherapy used for high-grade sarcomas, not surgery and radiotherapy alone.
The WHO bone classification lists dedifferentiated chordoma as a chordoma subtype defined by a high-grade sarcoma juxtaposed to conventional chordoma (Am J Surg Pathol 2020). In the ten-case series the tumours measured 2.8 to 24.5 cm (median 5.8), arose de novo or at recurrence including after radiotherapy in the sacrum (5), skull base (2), lumbar spine, mediastinum and as a lung metastasis, the dedifferentiated component made up 3 to 95 percent (median 60) and was pleomorphic to fibrosarcomatous, and by immunohistochemistry the conventional or chondroid component kept cytokeratin and brachyury while the dedifferentiated component lost both (Am J Surg Pathol 2020). The dedifferentiated component dictates survival, smaller areas carrying a better prognosis; it is more often diagnosed in recurrences and after radiotherapy but arises de novo in a few (JBJS British 2008).
How it differs from its parent: loss of brachyury in the sarcomatous part, rapid growth and early metastasis against the slow course of conventional chordoma, and a treatment plan that borrows from high-grade soft tissue sarcoma.
How common: about 1 percent of chordomas (Am J Surg Pathol 2020).
Treatment: en bloc resection where possible, radiotherapy (proton or carbon ion as on the parent page) and anthracycline-based chemotherapy for the sarcomatous component, borrowed from the sarcoma page; no trial exists in the subtype.
Under 1 percent of chordomas: 10 cases among more than 1,000 chordomas surveyed at one centre, seven men and three women aged 15 to 80 (median 54) (Am J Surg Pathol 2020).
Bone sarcomas favour the fast-growing ends of long bones (osteosarcoma) or the shaft (Ewing), soft tissue sarcomas the deep muscle compartments; spread is through the blood to the lungs, rarely via lymph nodes.
Lymph node spread is rare (except epithelioid, synovial, clear cell and rhabdomyosarcoma); sarcomas go through the blood to the lungs.
Same organ: Adamantinoma of bone, Poorly differentiated chordoma (SMARCB1-deficient), Desmoplastic small round cell tumour, Leiomyosarcoma, Liposarcoma, Synovial sarcoma, Sarcomas (soft tissue, bone, GIST), Osteosarcoma, Ewing sarcoma, Rhabdomyosarcoma, Chordoma, Desmoid tumour, Tenosynovial giant cell tumour (TGCT), Epithelioid sarcoma, Vascular tumours (angiosarcoma, epithelioid haemangioendothelioma, kaposiform haemangioendothelioma), Chondrosarcoma, Angiosarcoma, Undifferentiated pleomorphic sarcoma (UPS), Myxofibrosarcoma, Alveolar soft part sarcoma, Perivascular epithelioid cell tumour (PEComa), Epithelioid haemangioendothelioma, Malignant peripheral nerve sheath tumour (MPNST), Retroperitoneal sarcoma, Soft tissue sarcoma of the extremity (localised and advanced)
En bloc resection, radiotherapy as on the chordoma page, and anthracycline-based chemotherapy for the sarcomatous component; no trial in the subtype.
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Query for this cancer: (TITLE:"Dedifferentiated chordoma" OR ABSTRACT:"Dedifferentiated chordoma" OR TITLE:"Chordoma with sarcomatous transformation" OR ABSTRACT:"Chordoma with sarcomatous transformation" OR TITLE:"Dedifferentiated chordoma high-grade sarcoma in a chordoma" OR ABSTRACT:"Dedifferentiated chordoma high-grade sarcoma in a chordoma") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Dedifferentiated chordoma, not a curated reading list.
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Bleeding that will not stop, black or bloody stools, or unexplained bruising when platelets are expected to be low.
Cumulative dose: risk rises steeply above 400-550 mg/m² (see the anthracycline calculator).
Reduce by 50% for bilirubin 20-50 µmol/L and 75% for 50-85 µmol/L.
Heart damage from cancer treatment: anthracyclines weaken the heart muscle permanently in a dose-related way, trastuzumab does so reversibly, and some kinase inhibitors raise blood pressure or disturb rhythm. Heart function (LVEF) is monitored by ultrasound during treatment.
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