Poorly differentiated chordomas are highly aggressive poorly differentiated notochordal tumors with a loss of SMARCB1 expression.
On this page:
Epidemiology
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.
Diagnosis
The diagnosis is based on a combination of pathological and typical imaging features 1.
Diagnostic criteria
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 presentation
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
Complications of poorly differentiated chordomas include brainstem or spinal cord compression as well as distant metastases 2-4.
Pathology
Poorly differentiated chordomas are malignant notochordal bone tumors arising in the axial skeleton 1.
Etiology
The etiology of poorly differentiated chordomas is unknown 1.
Location
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.
Macroscopic appearance
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.
Microscopic appearance
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
frequent mitoses
absent or scarce physaliphorous cells
scarce extracellular myxoid matrix
apparent geographical necrosis
Immunophenotype
A loss in SMARCB1 (INI1) expression is a diagnostic criterion. Otherwise, tumors are positive for cytokeratin and brachyury 1-5.
Radiographic features
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.
CT
On CT tumors have been described with a lytic appearance 1,2.
MRI
MRI features of the tumors have been described as heterogeneous often multilobulated with mass effect on adjacent structures 1-3.
Signal characteristics
T1: heterogeneous
T2: heterogeneous
T1C+ (Gd): moderate to high heterogeneous enhancement
Radiology report
The radiological report should include a description of the following:
form and location
tumor margins and transition zone
cortical destruction
extension into the adjacent structures
associated complications
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.
Differential diagnosis
Condition or tumors that might mimic poorly differentiated chordomas include the following 1,2: