Benign notochordal cell tumors are vertebral lesions that are usually asymptomatic and discovered incidentally on imaging of the head or spine. As this is a poorly-recognized entity, it can often be confused with aggressive vertebral lesions, such as a chordoma, when it is seen on imaging.
On this page:
Terminology
Initially, the term vertebral intraosseous chordoma was used 7, although given that the relationship between these lesions and chordomas remains uncertain it is probably best to avoid this term. Other terms that have been used include giant (vertebral) notochordal rest and giant notochordal hamartoma (of intraosseous origin) 3,9.
Diagnosis
There no defined diagnostic criteria for benign notochordal cell tumor although the following are generally accepted 9:
no neurological symptoms
well-corticated margins
<35 mm in size
no enhancement on imaging
no soft tissue extension or dural penetration
no progression on scans
histologic absence of extracellular myxoid matrix and a low Ki67 index if biopsy performed
Epidemiology
Autopsy studies show benign notochordal cell tumors are extremely common with a reported incidence of up to 20% in cadaveric specimens 1. While only the larger of these lesions can be seen on imaging it is felt they are under-reported 2.
Clinical presentation
The vast majority of lesions are asymptomatic but a small proportion of patients can present with chronic back pain and coccydynia 2.
Pathology
Location
The distribution is similar to chordomas:
clivus (50%)
vertebrae
sacrum/coccyx
Radiographic features
CT
vertebral body sclerosis: can extend to the cortex or involve the entire vertebra
preserved trabeculae
no cortical destruction
MRI
-
well-defined osseous lesions
T1: hypo- or isointense; may demonstrate hyperintense intra-lesional punctiform foci representing fat lobules due to entrapped bone marrow
T2: hyperintense
T1 C+ (Gd): usually no enhancement (enhancement is considered an atypical feature) 9
DWI/ADC: no restricted diffusion
no soft tissue mass
Nuclear medicine
Often show no uptake on bone scintigraphy.
Treatment and prognosis
While there is a consensus that no specific treatment is required for asymptomatic lesions, the long-term malignant potential of benign notochordal cell tumors to transform into chordomas is not known and many advocate interval follow-ups 5.
Surgical resection or biopsy is generally reserved for lesions with atypical imaging features 9.
In most instances they are quiescent but reports of these tumors co-existing with chordomas or perhaps degenerating/transforming into chordomas exist 8,9.
Differential diagnosis
-
chordoma 3
bony destruction on CT
soft tissue mass
enhance on MRI
-
clivus
small and often pedunculated
notochordal vestiges of the intervertebral disc