Extramedullary plasmacytoma: clinical and histopathologic study

Abstract

$\text{Purpose}$: To review the histories of extramedullary plasmacytoma patients diagnosed in Slovenia between 1969 and 1999, to determine the relationship between radiotherapy (XRT) dose and local tumor control, and to clarify the role of elective nodal XRT and the prognostic value of Bartl’s histologic grading criteria (originally devised for multiple myeloma [MM]).

$\text{Methods and Materials}$: The database of the Cancer Registry of Slovenia was used for the identification of patients. The inclusion criteria were as follows: bone marrow biopsy showing less than 10% plasma cells, normal skeletal survey, and immunohistochemically determined tumor monoclonality. Simulation/portal films were reviewed to assess the extent of elective nodal XRT.

$\text{Results}$: Twenty-six patients with 31 tumors fulfilled the inclusion criteria. In 4 patients, nine metachronously appearing solitary tumors were diagnosed. The head-and-neck region and other body sites were the sites of origin of primary tumors in 84% and 16% of patients, respectively, whereas in the two regions, regional disease was seen in 15% and 60% of patients, respectively. Therapy was as follows: XRT, 12 patients; surgery and postoperative XRT, 15 patients; and surgery, 4 patients. Ultimate local and regional control rates were 90% and 97%, respectively, and MM developed in 2 (8%) patients. The 10-year disease-specific and overall survival rates were 87% and 61%, respectively. The analysis of the dose-effect relationship showed that more conservative treatment is justified: for macroscopic disease, 40–50 Gy (2 Gy/day), adjusted to the bulk of disease; for microscopic disease, 36–40 Gy; after R0 surgery, no XRT is required, but close observation is needed. No attempts should be made to treat uninvolved nodal regions. Using Bartl’s histologic grading criteria, trends were detected in patients with higher tumor grades: regional lymph node involvement (p = 0.04) and shorter disease-specific survival (p = 0.08).

$\text{Conclusions}$: Extramedullary plasmacytoma is a highly curable disease when XRT is used with or without previous surgery. The rate of conversion to MM is low. Moderate-dose XRT using limited fields is recommended. The prognostic value of Bartl’s grading system needs further evaluation.

Introduction

Extramedullary plasmacytoma (EMP) is a rare disease, histopathologically characterized by infiltrates of plasma cells of diverse maturity and by their monoclonal immunoglobulin products. Together with solitary plasmacytoma of the bone (SPB) and multiple myeloma (MM), they form a group of plasma cell neoplasms belonging to the category of B-cell neoplasms (1). EMP accounts for up to 3% of plasma cell tumors, yielding the EMP:SPB:MM incidence ratio of approximately 1:2:40 2, 3, 4, 5.

EMP is typically presented as a well-localized submucosal mass or swelling, sometimes with polypoidal configuration. According to the results of extensive literature review on EMP reported by Alexiou et al. (6), it occurs in the upper aerodigestive tract in more than 80% of patients, most often in the nasal cavity, paranasal sinuses, nasopharynx, tonsils, and larynx. Additional characteristics of EMP are male predominance and advanced age at presentation. Regional nodes are invaded in less than 10% of patients, and in approximately 16% of patients, the disease progresses to MM (6).

Besides its natural history, which hasn’t yet been clearly defined, EMP still seems to be a diagnostic and therapeutic challenge. Traditionally, because of the proven radiosensitivity of the disease, radiotherapy (XRT) plays a pivotal role in the treatment of EMP, even though the optimal dose and the role of elective irradiation of regional lymphatics are still a matter of debate (7). Surgery also can be considered as a first-line therapy to avoid long-term sequelae of XRT 6, 8. It is, however, more often employed as a salvage procedure after XRT for persistent or recurrent tumors. The role of chemotherapy in the treatment of primary tumors or recurrent disease, or in preventing or delaying progression to MM is controversial 4, 9, 10. Because the reported local tumor control rates approach 100% after radical therapy 3, 4, 5, 6, 8, 9, the overall survival rate ranges widely, from 45% to 100% (at 10 years), depending in the first place upon a degree of conversion to MM 2, 4, 5.

The aim of the present study was to review the experience with EMP in the patient population that was seen at the Institute of Oncology, Ljubljana, Slovenia between 1969 and 1999. Special emphasis was placed on: (1) the relationship between the irradiation dose and local tumor control, (2) the role of elective nodal irradiation, and (3) the prognostic value of Bartl’s histologic grading criteria originally devised for MM (11).