Dedifferentiated chordoma: a case report of a rare subtype of chordoma

Chordoma is a malignant tumour showing notochordal differentiation with three identified subtypes including chordoma not otherwise specified, chondroid chordoma and dedifferentiated chordoma. Dedifferentiated chordoma is rare and carries the worst prognosis of all subtypes due to rapid progression and potential for metastases. It is characterized by a high-grade sarcomatous component juxtaposed to conventional chordoma. We report a case of a dedifferentiated chordoma in a 71 year old woman who presented with pain in the lower back, numbness of feet and loss of weight of recent onset. Per-rectal examination revealed a soft tissue mass in the presacral region while imaging showed a solid and cystic lesion with calcifications in the presacral region. The radiological impression was of a retro rectal cystic hamartoma, an epidermoid cyst, or a chronic abscess. The resected specimen comprised a lobulated mass of soft, gelatinous tissue with haemorrhage and necrosis. Microscopy showed a biphasic tumour composed of conventional chordoma juxtaposed with high-grade sarcomatous component. Morphology and immunohistochemistry were compatible with a chordoma with a focal high-grade spindle cell sarcomatous component in keeping with a dedifferentiated chordoma.