Extramedullary plasmacytoma

Extramedullary plasmacytoma, also known as extraosseous plasmacytoma, are the less common form of solitary plasmacytoma, manifesting as isolated plasma cell tumors located at a non-osseous site. In contrast to multiple myeloma (MM), solitary plasmacytoma have little or no systemic bone marrow involvement. 

They most commonly occur in the head and neck region, rarely along the digestive tract, lung, or extremities.

Epidemiology

• solitary plasmacytoma overall represent only 3-6% of all plasma cell disorders (i.e. multiple myeloma, plasma cell leukemia) ⁴
• ~1/3 of solitary plasmacytoma are extramedullary (~2% of all plasma cell disorders overall) ^4,5
• occur most commonly during the fourth through to seventh decades of life
• more common in men than women

Clinical presentation

Non-specific symptoms such as pain caused by local mass effect and compression of the surrounding organs by the extramedullary plasmacytoma ⁷.

Pathology

A plasmacytoma lesion is composed of monoclonal plasma cells arranged in clusters or sheets. In contradistinction to MM, diagnosis of plasmacytoma requires exclusion of significant bone marrow involvement.

Location

Although plasmacytoma more commonly occur within bone, they may also occur in other organs throughout the body. 

Extramedullary plasmacytoma can involve almost any location outside the bone marrow, but the following are most often recognized:

• head and neck - by far most common ^5,6
  • mostly involving sinuses, nasopharynx, oropharynx ⁵
• rare
  • digestive tract ⁶
  • lungs ⁶
  • upper/lower extremities ⁶
  • retroperitoneal 
  • skin ⁷

Associations

• hyperamylasaemia may be an associated finding

Markers

Serum amylase levels may be used as a tumour marker for monitoring tumour progression and treatment response. 

Radiographic features

CT / MRI

Cross-sectional imaging demonstrates non-specific, well-circumscribed or infiltrative, homogeneously enhancing soft tissue masses or lymphadenopathy. 

There may be a mass effect on other adjacent structures such as vessels, or there may be an invasion of adjacent organs.

Nuclear medicine

Active lesions demonstrate uptake of FDG on PET imaging.

Treatment and prognosis

Treatment typically is complete surgical resection, sometimes in combination with radiation therapy⁷.

Prognosis for extramedullary plasmacytoma is considered better than for solitary bone plasmacytoma ^4,5.

The rate of progression to multiple myeloma (MM) varies from 10% to 30%.

See also

• extraosseous myeloma