Thursday, December 15, 2011

Benign Notochordal Cell Tumors

Benign notochordal cell tumors are recently discovered intraosseous lesions of notochordal cell origin that are usually asymptomatic or indolent. Synonyms for this tumor include benign chordoma, giant notochordal rest, giant notochordal hamartoma of intraosseous origin, notochordal hamartoma, and ecchordosis physaliphora vertebralis.

These tumors can have histologic findings that overlap with those of chordomas. It has been suggested that benign notochordal cell tumors may be precursors of chordomas, but the evidence for this seems to be lacking at this point.

Like chordomas, benign notochordal cell tumors are most commonly found at the midline in the sacro-coccygeal region and the base of the skull.

On radiography, these are ill-defined and sclerotic lesions, sometimes with the appearance of an ivory vertebra. Radiographs can be normal, however. Regardless of the visibility of these lesions on radiographs, bone expansion should not be seen.

CT can also be normal or reveal sclerosis ranging from mild to severe. Trabecular and cortical destruction should not be seen. The lesions can be central in the vertebral body, extend to the cortex, or occupy the entirety of the vertebral body, resulting in an ivory vertebra.

The lesions are homogeneously hypointense on T1-weighted images, and homogeneously iso- to hyperintense on T2-weighted images. No significant enhancement is typically seen, although the lesion in our case has mild enhancement. Extraosseous extension should not be seen.

Chordomas may resemble benign notochordal cell tumors with cellular atypia on biopsy. Imaging can help in differentiating the two by remembering that in contrast to chordomas, benign notochordal cell tumors are not typically osteolytic and may have sclerosis. In addition, chordomas can have a soft tissue mass, while benign notochordal cell tumors typically do not.


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