Poorly differentiated chordoma
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Poorly differentiated chordomas are highly aggressive poorly differentiated notochordal tumors with a loss of SMARCB1 expression.
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Poorly differentiated chordomas are very rare tumors typically seen in children and young adults under the age of 30 years. Females are more frequently affected 1-3.
The diagnosis is based on a combination of pathological and typical imaging features 1.
Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:
typical imaging features of a bone tumor
poorly differentiated neoplasm
location in the axial skeleton
no SMARCB1 (INI1) expression
positive immunohistochemistry for keratin and brachyury
Clinical signs and symptoms are usually nonspecific and include headache, weight loss and cranial nerve-related symptoms such as pain and dysesthesia 1,2.
Complications of poorly differentiated chordomas include brainstem or spinal cord compression as well as distant metastases 2-4.
Poorly differentiated chordomas are malignant notochordal bone tumors arising in the axial skeleton 1.
The etiology of poorly differentiated chordomas is unknown 1.
Poorly differentiated chordomas usually arise from the clivus or the skull base, the cervical spine and only on rare occasions from the sacrococcygeal area 1-3.
Poorly differentiated chordomas are usually characterized by a destructive multilobulated and possibly well-demarcated appearance. They might be quite large at the time of diagnosis 1.
Histological features of poorly differentiated chordomas include 1-5:
sheets of epithelioid cells with focal rhabdoid morphology
abundant eosinophilic cytoplasm
mild to moderate nuclear pleomorphism
absent or scarce physaliphorous cells
scarce extracellular myxoid matrix
apparent geographical necrosis
A loss in SMARCB1 (INI1) expression is a diagnostic criterion. Otherwise, tumors are positive for cytokeratin and brachyury 1-5.
On imaging, poorly differentiated chordomas have been described as destructive tumors arising from the bony axial skeleton with extension into the adjacent tissues 1-3.
On CT tumors have been described with a lytic appearance 1,2.
MRI features of the tumors have been described as heterogeneous often multilobulated with mass effect on adjacent structures 1-3.
T1C+ (Gd): moderate to high heterogeneous enhancement
The radiological report should include a description of the following:
form and location
tumor margins and transition zone
extension into the adjacent structures
Treatment and prognosis
The prognosis is poor and worse than the prognosis of conventional chordoma with a high rate of local recurrence and distant metastasis 2-4. Management is multimodal and comprises surgical excision, radiation therapy and chemotherapy 1,3.
History and etymology
Poorly differentiated chordomas have been added as a distinct entity into the WHO classification of bone tumors in 2020 1,5. At present, it is difficult to get to the bottom of their exact history. The loss of SMARCB1/INI1 expression in those highly aggressive notochordal tumors was first reported by a group around the American pathologist Bret C Mobley in 2010 6.
Condition or tumors that might mimic poorly differentiated chordomas include the following 1,2:
- 1. Nielsen GP, Dickson BC, Tirabosco R. Poorly differentiated chordoma. In: WHO Classification of Tumours Editorial Board. Soft tissue and bone tumours. Lyon (France): International Agency for Research on Cancer; 2020. (WHO classification of tumours series, 5th ed.; vol. 3). https://publications.iarc.fr
- 2. Shih A, Cote G, Chebib I et al. Clinicopathologic Characteristics of Poorly Differentiated Chordoma. Mod Pathol. 2018;31(8):1237-45. doi:10.1038/s41379-018-0002-1 - Pubmed
- 3. Yeter H, Kosemehmetoglu K, Soylemezoglu F. Poorly Differentiated Chordoma: Review of 53 Cases. APMIS. 2019;127(9):607-15. doi:10.1111/apm.12978 - Pubmed
- 4. Jaber O & Ashhab M. Metastatic Poorly Differentiated Chordoma: The Eyes Do Not See What the Mind Does Not Know. Autops Case Rep. 2019;9(4):e2019120. doi:10.4322/acr.2019.120 - Pubmed
- 5. Ulici V & Hart J. Chordoma. Arch Pathol Lab Med. 2022;146(3):386-95. doi:10.5858/arpa.2020-0258-RA - Pubmed
- 6. Mobley B, McKenney J, Bangs C et al. Loss of SMARCB1/INI1 Expression in Poorly Differentiated Chordomas. Acta Neuropathol. 2010;120(6):745-53. doi:10.1007/s00401-010-0767-x - Pubmed