[Isolated idiopathic amyloid tumor of the sacrum. An important differential diagnosis].

Primary amyloidosis may present as a pseudotumoral mass. Often associated with myeloma or paraproteinemia, it may also be isolated, without preexisting or associated disease. Isolated pseudotumoral bone involvement is rare and especially in the spine. Differential diagnosis is very important, because the prognosis of primary amyloidoma is excellent after surgical removal.