Radiological signs and spinal involvement
Although the overall MRI semiotics of plasmacytoma are considered nonspecific, a solitary plasmacytoma of bone (solitary plasmacytoma of bone, SPB) in the spine exhibits several highly characteristic manifestations.
Key radiological findings include:
- «Mini-brain» appearance (mini-brain appearance). This occurs due to thickened peripheral bone trabeculae projecting deep into the bone marrow cavity. This sign is visualized particularly clearly on axial MRI slices (T1-weighted spin-echo sequence) and on CT.
- Vertical trabeculation (vertical trabeculation). Pronounced striation within the body of the affected vertebra, best identified on coronal multiplanar reformation (MPR) CT scans.
- Sparing of the intervertebral disc. Tumor extension across the intervertebral disc (disc space) is extremely rare. This fact is crucial for differential diagnosis with infectious processes (spondylitis), which frequently destroy the disc.
- Pathological fractures. Involvement of the vertebral body significantly reduces its mechanical strength, predictably leading to pathological collapse.
Diagnostic algorithm and staging
Because the radiological picture can mimic other neoplasms, the definitive clinical diagnosis is established exclusively on a morphological basis. To achieve this, percutaneous needle biopsy is performed strictly under image guidance (image-guided percutaneous needle biopsy).
Following histological confirmation of the diagnosis, the primary task is to rule out a disseminated process:
- MRI of the entire spine and pelvis. This is a mandatory staging step. Screening of the thoracic and lumbar spine allows the detection of additional asymptomatic lesions in approximately 1/3 of cases.
- PET-CT (PET-CT). An effective whole-body imaging method. The method demonstrates high radiopharmaceutical uptake (fluorodeoxyglucose, high FDG avidity) directly within lytic lesions, such as those in the posterior iliac bone, reliably revealing the extent of the disease.
Multiple Myeloma
The disease is widespread in nature and represents the predominant form of plasma cell neoplasms (plasma cell neoplasm).
Epidemiological status:
- It is the most common primary malignant bone neoplasm.
- Myeloma accounts for approximately 15% of all hematological malignancies.
- In the structure of all oncological diseases, it accounts for approximately 1.3%.
Clinical and demographic features:
- Age. The disease typically affects the older age group: 75% of patients are older than 50 years at the time of detection. The median age at diagnosis is 66 years. Early-onset cases are rare — only about 3% of patients are younger than 40 years.
- Gender. There is a pronounced gender predisposition. Men are affected significantly more often than women (a ratio of 2:1).
Briefly: answers to topical questions
Which skeletal bones, besides the spine and pelvis, are most frequently affected in multiple myeloma?
In multiple myeloma, typical sites of skeletal involvement are the axial skeleton and the proximal ends of long tubular bones.
Besides the spine and pelvis, the sources explicitly indicate:
- proximal ends of long tubular bones;
- skull bones — most characteristically presenting with a classical radiographic picture of well-defined «punched-out» lytic lesions (punched-out lesions).
How to differentiate solitary plasmacytoma from osteolytic vertebral metastases using CT and MRI data?
Differentiating solitary plasmacytoma from metastases is aided by evaluating the involvement of adjacent structures and specific radiological signs.
- «Mini-brain» appearance (mini brain appearance) — a typical sign on axial CT and MRI slices. It presents as curvilinear low-signal structures partially traversing the vertebral body, caused by cortical bone and peripheral trabecular thickening.
- Involvement of adjacent structures — extension of the process across the intervertebral disc (disc space) and into adjacent vertebrae is a rare feature, which aids in differential diagnosis from metastases.
What are the signal characteristics of plasmacytoma on T2-weighted and STIR MRI sequences?
On MRI, the signal characteristics of plasmacytoma are generally nonspecific.
- T2-weighted imaging — the tumor exhibits high signal intensity.
- STIR — the provided sources contain no information regarding the signal characteristics of plasmacytoma on this sequence.
Additionally, it is known that T1-weighted images show low signal intensity, and contrast administration reveals homogeneous, intense enhancement.
What specific blood and urine laboratory markers must be checked when radiological signs of plasmacytoma are detected?
The provided sources do not specify laboratory markers that need to be checked specifically upon the detection of radiological signs of plasmacytoma.
For plasmacytoma, the sources explicitly indicate:
- the definitive diagnosis is established using image-guided percutaneous needle biopsy;
- following diagnosis, MRI of the entire spine and pelvis is indicated to detect additional lesions;
- PET-CT also effectively demonstrates additional lesions.
«Mini-brain» sign — imagine that thickened trabeculae inside the vertebral body on an axial T1-weighted image wind similarly to the sulci and gyri of the cerebral cortex.
Class and exam questions
How to reliably confirm the diagnosis of plasmacytoma?
The gold standard is a percutaneous needle biopsy of the suspicious lesion, performed under diagnostic imaging guidance.
Why is MRI of the pelvis and entire spine strictly ordered when a lesion is detected in a vertebra?
This is necessary to search for additional lesions. In approximately 33% of cases, such screening reveals new lesions, which changes the stage of the disease.
Does plasmacytoma affect the intervertebral disc?
No, tumor extension into the intervertebral disc is a very rare feature, which helps distinguish plasmacytoma from infectious spinal involvement.
Which age group is most susceptible to multiple myeloma?
These are predominantly patients older than 50 years (75% of cases), with a median age at diagnosis of 66 years.
What else to study on this topic
- Specifics of performing image-guided percutaneous needle biopsy
- Differential diagnosis of the «mini-brain» sign with other tumors
- Comparison of MRI and PET-CT sensitivity in searching for lytic lesions
- Pathogenesis of vertical trabeculation formation in plasma cell neoplasms
- Radiological signs of pathological vertebral body collapse (fracture)
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