ⅠINTRODUCTION
A plasmacytoma is a rare malignancy composed of plasma cells.1) Plasmacytomas are unifocal, monoclonal, neoplastic proliferations that usually arise within bone; however, an extramedullary plasmacytoma (EMP) can occur in soft tissues. The majority of primary EMPs occur in the head and neck region, especially in the upper respiratory tract and oral cavity. It is believed that EMPs ultimately develop into multiple myeloma (MM). We present a case report of a 52-year-old female with an EMP.
ⅡCASE REPORT
A 52-year-old female was referred to the Department of Oral and Maxillofacial Surgery for evaluation of soft palate swelling. The patient had no pertinent medical history.
The initial workup included a complete blood cell count (CBC), electrolyte panel, and imaging studies. Laboratory results showed no signs of anemia, hypercalcemia, or renal insufficiency. Upon clinical examination, a 1.5 x 1 cm, reddish, non-tender mass with telangiectasia was found near the midline of the soft palate (Fig. 1A, 2A). There were no signs of cervical lymphadenopathy.
Magnetic resonance (MR) imaging showed an enhancing mass with poorly demarcated radiographic margins causing bulging of the soft palate. The lesion had a hypointense T2 signal. Benign neoplasms such as a mucocele were ruled out due to the evenly distributed enhancement of the lesion. No enlarged or irregular cervical lymph nodes were found radiographically (Figs. 1B, 1C).
An excisional biopsy was performed under general anesthesia. The resected mass was 1.8 x 1.4 x 1.1 cm in size and was filled with solid whitish material (Fig. 2A, 2B). Final pathologic diagnosis was an EMP of the soft palate with partial involvement of the resection margin.
Microscopic examination showed sheets of plasma cells with varying degrees of differentiation in a monomorphic plasmacytoma pattern (Figs. 3 A, B, C, D). Immunohistochemical studies confirmed the monoclonality of the plasma cells. Immunohistochemistry with antibodies to kappa light chain was negative, but that with lambda chain antibodies was positive (Figs. 3 E, F). Ki-67 staining was present in fewer than 1% of cells. Extensive plasma cell proliferation was observed and is a major indicator of a plasmacytoma. The resection margin, however, showed partial involvement of the tumor cells.
Postoperative and follow-up MR images showed no definite residual or recurrent lesion in the oral cavity and no significant cervical lymphadenopathy. Postoperative PET-CT imaging showed mild hypermetabolism in the left soft palate, which is most likely a postoperative change (Fig. 4A, 4B).
After pathologic diagnosis of malignancy, the patient was admitted to the Department of Oral and Maxillofacial Surgery for a formal workup. The patient was then referred to the Department of Radiation Oncology for consultation regarding postoperative radiation therapy (PORT). In order to rule out the possibility of multiple myeloma, a bone marrow exam with a chromosomal study was performed. The bone marrow exam was negative, thus excluding multiple myeloma. Radiation oncology recommended PORT for definitive care; however, the patient refused. The patient is currently under close observation for signs and symptoms of recurrence or metastases through regular follow-up visits and imaging studies. 1-year follow up MRI showed no definite residual or recurred lesion in the oral cavity and no significant cervical lymphadenopathy.
ⅢDISCUSSION
Extramedullary plasmactomas are rare soft tissue malignant neoplasms composed of plasma cells.1) EMPs account for approximately 1% to 2% of malignancies. They occur at a rate of 3.5/100,000 per year.2-4) Plasmacytomas present as multiple myeloma, solitary plasmacytoma of bone (SBP), or EMP.5-7) These tumors usually present clinically without evidence of tumor elsewhere. Although extraosseous plasma cell infiltrates are found in more than 2/3 of patients with multiple myeloma at autopsy, EMP is rarely (5%) the presenting manifestation.8-11) SMP differs from multiple myeloma in its lack of plasma cell infiltration in a random bone marrow biopsy. Unlike multiple myeloma, SMP patients usually show no signs of hypercalcemia, anemia or renal failure.14)
Patients with plasmacytoma of the oral cavity show symptoms like jaw pain, toothache, swelling, paresthesia, mobility of teeth, hemorrhage, and pathologic fracture of the involved bone. In this case, the patient complained of no symptoms other than swelling.5,12,13)
Radiographically, EMP can erode bone and might not be easily distinguishable from SBP.15) The lesion can be seen as a well-defined, unilocular radiolucency with no evidence of sclerotic borders or as a ragged radiolucency similar in appearance to multiple myeloma.14)
EMP shows histopathologic features identical to those of multiple myeloma, such as sheets of plasma cells showing different degrees of differentiation. Immunohistochemically, EMP seems to show lack or marked decrease of immunoreactivity for antibodies directed against cyclin D1 and CD56, compared to solitary plasmacytoma of bone.14)
Dissemination or progression to multiple myeloma occurs in up to 85% of patients in solitary plasmacytoma of bone. However, extramedullary plasmacytomas mostly remain well localized. Thus, EMP has a much better prognosis. Only 30% of patients with EMP progress to multiple myeloma, and 70% have a 10-year disease-free period after treatment.14) Local recurrence occurs in 6 - 10% of cases that have had adequate initial treatment.7,17,18) The reported 5-year overall survival rates for patients range from 40 – 85%.17,19,20)
The treatment option for solitary extramedullary plasmacytoma is radiotherapy at a dose of 4 to 50 Gy over a 4-week period.21,22) If solitary extramedullary plasmacytoma was resected completely as part of the diagnosis, the role of adjuvant radiotherapy is less clear. Small lesions can be cured with surgery alone, and if there is no suspicion of residual disease, adjuvant radiotherapy is not indicated. Adjuvant chemotherapy does not appear to improve the relapse rate or increase disease-free survival.23)
Investigation of patients with suspected plasma cell tumors should include a full workup to rule out multiple myeloma. Urinalysis for Bence-Jones protein, serum protein electrophoresis, serum electrophoresis, bilateral bone marrow examinations, and a skeletal survey are all essential to the diagnostic workup. Only when other systemic diseases have been ruled out can the diagnosis of SEP be entertained.16)
ⅣCONCLUSION
The pathologic exam in the present case resulted in a final diagnosis of extramedullary plasmacytoma with partial tumor involvement at the resection margin. Postoperative radiotherapy was recommended by radiation oncology; however, the patient refused further treatment. The patient is currently under close observation for signs and symptoms of recurrence or metastases through regular follow-up visits and imaging studies.
Although uncommon, EMPs are found in the palatal region. This clinically benign-appearing entity has the possibility of evolving into multiple myeloma. The diagnostic process entails a full multiple myeloma workup including urinalysis, serum analysis, and an invasive spinal marrow exam. Thus, when encountering a soft tissue mass in an unusual location, a thorough radiographic exam should precede surgical removal of the lesion, and the possibility of systemic involvement should be considered. When in doubt, prompt referral to an oral and maxillofacial surgery specialist or oncologist is strongly recommended for proper care and long-term follow-up.
