Plasmacytoma
Key Points
Plasma cell tumors are derived from a terminally differentiated cell in the B-lymphocyte lineage
They originate in the bone marrow during the maturation process from B-blasts to plasmablasts
Clinically, they present as multiple myeloma, as a solitary bone and extramedullary plasmacytoma without multiple myeloma, or as plasma cell leukemia
Eyelid plasmacytoma is a rare extramedullary form occurring in the conjunctiva, orbit, or in the eye
It is hypothesized that primary extramedullary plasmacytoma may represent a special type of marginal zone cell lymphoma with extensive plasmacytic differentiation initiated by inflammatory infiltrate
Eyelid lesions generally appear as a slow-growing, well-circumscribed, painless, firm, mobile, discrete, violaceous, or reddish-blue nodule that may be associated with eyelid swelling and ecchymosis
Management must begin with systemic evaluation to rule out multiple myeloma or other lymphoproliferative disorders
Radiation therapy is considered the treatment of choice with a response rate as high as 93%
Surgical excision is an alternative option and chemotherapy is used for cases that progress to multiple myeloma
For eyelid lesions the prognosis is very good, but progression to multiple myeloma is reported in about 14% of cases
Plasma cell tumors are neoplasms derived from a terminally differentiated cell in the B-lymphocyte lineage, which is generally believed to only undergo a limited number of cell divisions before it exits the cell cycle.1 They originate in the bone marrow during the maturation process from B-blasts to plasmablasts that dedifferentiate and transform into malignant plasmablasts.2,3 These tumors usually develop in the bone marrow and less commonly in extramedullary sites.
Plasma cell neoplasms can present clinically in several different forms including multiple myeloma, solitary bone and extramedullary plasmacytoma without multiple myeloma, and plasma cell leukemia.4 Multiple myeloma is usually located in the bone marrow,5 but neoplastic cells can invade or migrate to soft tissues including the skin.6,7 Plasmacytomas are immunoproliferative, monoclonal plasma cell tumors that are classified as a non-Hodgkin lymphoma.8 While most are associated with multiple myeloma, others are solitary lesions not associated with any systemic disease. Solitary plasmacytomas are rare and are further subclassified as either solitary plasmacytoma of bone (SPB) or as extramedullary plasmacytoma of soft tissue (EMP).
In a large study of 1354 patients with plasma cell neoplasms, 94% had multiple myeloma, 4% had SPB, and 2% had EMP.9 In a recent Swedish study,10 solitary bone plasmacytoma in vertebrae, femurs, pelvis, and ribs represented 70% of all solitary plasmacytomas.
Extramedullary plasmacytomas are lesions that are not associated with a bony focus or any evidence of multiple myeloma.8,11 They are seen most often in the upper respiratory passages (80%) and less frequently in the gastrointestinal and genitourinary tracts, skin, lung, kidney, bladder, breast, thyroid, lymph nodes, and other locations.6,8,12,13,14,15,16,17,18,19 Patients with a solitary plasmacytoma are usually aged from 50 to 80 years, but rarely this tumor can be seen in children.20 Occurrence on the eyelid is uncommon,2,6,21,22,23,24,25,26 and very rare cases have been described in the conjunctiva,27,28,29,30 orbit,20,24,31,32,33 and even in the eye.6,34
Solitary plasmacytoma has a predilection to progress to multiple myeloma. This is especially true for SPB with an overall progression rate of 30% to 40%. However, patients with SPB plus evidence of occult clonal bone marrow plasma cell involvement by flow cytometry in areas distant from the plasmacytoma have a greater progression rate of 60% to 70%.35,36 In contrast, the progression of EMP to multiple myeloma is less, with most reported rates ranging between 9 and 14%,8,37,38,39,40 although Liebross et al9 reported a rate of 32%. Risk factors that increase the likelihood of progression include presence of the lesion in bone, larger tumors greater than 5 cm in diameter, lymph node involvement, and older age of patients.41
Etiology and Pathogenesis
In 1976, Wiltshaw40 proposed that EMP is distinct from SPB and multiple myeloma, based on several distinct differences. These included a predilection for EMP to arise from plasma cells located in mucosal surfaces, particularly the upper pulmonary passages, as opposed to SPB and multiple myeloma which originate from bone marrow plasma cells. Also, while most cases of SPB will eventually progress to multiple myeloma of bone, when EMP progresses, it more often spreads to other soft tissue sites. Also, the overall prognosis of EMP is significantly better with a longer median survival period.42 The definition and classification adopted in a recent WHO update also support a divergence of EMP from SPB based on their biologic differences.43
It has been hypothesized that primary EMP, whether occurring in mucosal sites or lymph nodes, may represent a
special type of marginal zone cell lymphoma with extensive plasmacytic differentiation.44 Like EMP, marginal zone B cell lymphomas (MZL) are found in nodal (monocytoid B cell lymphoma) and extranodal (mucosa-associated lymphoid tissue lymphoma) sites,44 and plasma cell differentiation is a common feature seen in MZL.44,45,46,47,48,49 It is also interesting to note that inflammatory cells can be seen on histopathological examination of EMP,20,21,23 and it has been postulated that an inflammatory infiltrate could initiate a monoclonal plasma cell proliferation.50
special type of marginal zone cell lymphoma with extensive plasmacytic differentiation.44 Like EMP, marginal zone B cell lymphomas (MZL) are found in nodal (monocytoid B cell lymphoma) and extranodal (mucosa-associated lymphoid tissue lymphoma) sites,44 and plasma cell differentiation is a common feature seen in MZL.44,45,46,47,48,49 It is also interesting to note that inflammatory cells can be seen on histopathological examination of EMP,20,21,23 and it has been postulated that an inflammatory infiltrate could initiate a monoclonal plasma cell proliferation.50
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