Summary: A 68-year-old male currently undergoing workup for an enlarged prostate presents with back
pain. A computed tomography (CT) examination of the lumbar spine is ordered for
Axial and sagittal CT images as well as sagittal T1-weighted pre- and postcontrast, T2-weighted, and STIR
images are provided. The CT images demonstrate a mildly expansile lytic lesion involving the vertebral body with extension into the left pedicle. There is bulging of the posterior aspect of the vertebral body with preservation of the remaining cortex. Numerous thickened cortical struts are present within the lytic lesion. The magnetic resonance (MR) images demonstrate the lesion is mildly hyperintense to muscle on T1-weighted images, and hyperintense to skeletal muscle on T2-weighted and STIR images. Postcontrast images demonstrate mild homogenous enhancement.
Plasmacytomas are solitary monoclonal plasma cell tumors,
which may occur within bones or soft tissue. The spine is the most common site
of involvement, seen in 34% to 72% of cases, most commonly within the thoracic,
lumbar, sacral, and cervical vertebrae in descending order of frequency. Other
locations include ribs, long bones, sternum, clavicle, pelvis, and scapula. The
mean age of presentation is 55 years with men being affected at twice the
incidence of women. Patients most frequently present with pain, often due to
pathologic fracture, or spinal cord/nerve root compression syndrome. Lesions in
superficial bones may also present with a mass on physical examination, with or
The diagnostic criteria for a solitary bone plasmacytoma consist of: 1) solitary
lesion with biopsy demonstrating plasma cells; 2) absence of other lesions as
proven by a negative skeletal survey and MRI of the spine, pelvis, and proximal
femurs/humeri; 3) negative clonal cells (plasma cells <5%) in marrow
aspirate; 4) no anemia, hypercalcemia, or renal impairment attributable to
myeloma; 5) low or absent serum/urine monoclonal proteins; and 6) preserved
levels of uninvolved immunoglobulins.
Imaging findings of vertebral body plasmacytomas include a lytic lesion with or without dense vertical striations,
or a pathologic compression fracture on plain film. CT imaging findings again
include a destructive lesion, which most often includes the posterior elements.
A soft tissue component may be present and vertical struts may be better
appreciated than on plain film. The vertical struts are presumably secondary to
compensatory hypertrophy of the remaining trabecular bone. The presence of
thickened vertical struts within an expansile lytic lesion on axial CT/MR
images has been termed the “mini brain” appearance. Alternatively, a collapsed
vertebral body may also be seen with evidence of a lytic lesion, best
appreciated within the uncollapsed posterior elements. On MR images, the
lesions are usually iso/hypointense to skeletal muscle on T1-weighted images,
iso/hyperintense on T2-weighted images, and hyperintense on STIR images. Post
contrast images demonstrate mild to moderate diffuse enhancement.
Solitary bone plasmacytomas typically have an indolent course. Treatment consists of tumor excision with
adjuvant radiation. The use of chemotherapy is controversial, but may be used
at some centers. Local recurrence is uncommon, but approximately half of
patients will eventually develop overt multiple myeloma.
- Major NM, Helms CA, Richardson WJ. The
"mini brain": plasmacytoma in a vertebral body on MR imaging. AJR Am J Roentgenol. 2000;175:261-263.
- Ooi GC, Chim JC, Au WY, et-al. Radiologic manifestations of primary solitary extramedullary and multiple solitary plasmacytomas. AJR Am J Roentgenol. 2006;186:821-827.