Dedifferentiated sacral chordoma: a case report

Chordoma is a rare bone sarcoma. It has a predilection for the axial skeleton. There are three recognized histologic variants of chordoma; conventional, dedifferentiated and poorly differentiated. This case report highlights the rarity of dedifferentiated chordoma pertaining to its morphology and immunohistochemical staining. Case report: A 58 years old lady, initially was diagnosed as sacral chordoma, however she defaulted her follow-up. Patient then presented again after several months with increasing size of the sacral mass associated with pain and neurologic symptoms. On examination, the tumour is 40x30cm extending from L4 to the gluteal fold. Magnetic Resonance Imaging (MRI) revealed the mass has significantly increased in size compared to previous MRI. Tumour resection was done. Histologically, the tumour cells are arranged as lobules composed of physaliphorous cells. In areas, there is abrupt transition between conventional chordoma and dedifferentiated component. The cells from conventional chordoma are positive for CKAE1/AE3, EMA and S100 while the same markers are negative in dedifferentiated component. Discussion: The dedifferentiated chordoma accounts for less than 5% of all chordomas. Most of the symptoms are neurologic. Histologically, the tumor contains areas of conventional chordoma and high-grade sarcomatous component, in which these areas being admixed and sharply demarcated. Immunohistochemically, positivity for CK, EMA, and S100 are traditionally used to support the diagnosis of a chordoma. This panel is generally sufficient to exclude differential diagnoses of chordoma eg: chondrosarcoma and metastatic renal cell carcinoma. Conclusion: Dedifferentiated chordoma differs from conventional chordoma by the rapid growth of tumor and its potential for distant metastasis