Plasmablastic plasmacytoma of the breast

Abstract

Breast plasmacytomas are extremely rare entities that can be seen as primary malignant neoplasms in the absence of bone involvement or as secondary neoplasms from disseminated multiple myeloma. Clinicians should be aware of this entity, as it may mimic benign and malignant lesions in the breast. Microscopically, immature plasmacytomas may mimic other neoplasms, so caution should be made on histological examination to ensure the correct diagnosis and corresponding therapy. Here we present a case of a plasmablastic plasmacytoma of the breast in a 55-year-old woman that was originally thought to be an angiosarcoma.

Plasma cell dyscrasias are disorders of clonal plasma cells that typically secrete monoclonal immunoglobulin called paraprotein or M-protein. They are a diverse group of disorders that include monoclonal gammopathy of undetermined significance, plasma cell myeloma, plasmacytoma, immunoglobulin deposition disease, and osteosclerotic myeloma. In 2003, the International Myeloma Working Group recognized three entities of plasmacytoma: solitary plasmacytoma of bone, extramedullary plasmacytoma, and multiple solitary plasmacytomas that are either primary or recurrent. Breast plasmacytomas, in particular, are extremely rare and can present as a primary isolated tumor or as an extramedullary manifestation of multiple myeloma (1–4). Clinicians need to be aware of this entity as breast plasmacytomas, particularly the immature cell type, may be erroneously misdiagnosed as a carcinoma or sarcoma. Plasmacytomas may respond well to local radiation and/or chemotherapy, and 70% of patients remain disease free at 10 years (5).

CASE DESCRIPTION

In August 2016, a 55-year-old woman presented at an outside facility with a chief complaint of an upper outer quadrant left breast mass, measuring 7.5 × 5.5 cm on physical examination. Laboratory values were unremarkable, except for a low white blood cell count (4.5/L) and a low hematocrit level (35.9%). A diagnostic mammogram showed a round mass at the 1 o'clock position, posterior depth of the left breast. The patient had a core biopsy of the lesion. Pertinent immunostains that were positive included CD31, vimentin, and Ki-67, and on this basis, the lesion was favored to be an angiosarcoma. A right subclavian MediPort was placed shortly thereafter for intravenous access. No protein studies were done at this time.

The patient was referred to our institution in October 2016. Pertinent past medical history included a diagnosis of multiple myeloma with an autologous stem cell transplant in 2011. On physical examination, the mass measured approximately 11 × 8 cm and was mobile over the chest wall. There was no overlying skin fixation or axillary and supraclavicular lymphadenopathy. Our department was consulted for a second opinion on the core biopsy, and we were concerned for a possible plasmablastic plasmacytoma. In the interim, the patient was advised to undergo excision of the lesion, and due to its large size, a total mastectomy was recommended. Adjuvant radiation therapy was considered. A sentinel lymph node biopsy was to be performed at the time of surgery due to the possibility of a sarcoma from the original report. The patient agreed to the aforementioned procedures.

The sentinel lymph nodes and nipple-sparing left total mastectomy were evaluated by our pathology department. Grossly, the left breast lesion was well circumscribed, tan, and firm. It measured 8.8 × 8.5 × 6.0 cm and involved the upper inner and outer quadrants, spanning the 10 to 2 o'clock positions. Microscopic examination of the left breast lesion showed a solid mass of atypical cells with enlarged eccentric nuclei, prominent nucleoli, and faintly basophilic cytoplasm (Figures 1a, 1b). Moderate mitotic figures were identified. Atypical duct hyperplasia and malignancy were not seen. The tumor extended to the anterior margin and measured 0.3 mm from the posterior margin. Because of our concern that the original biopsy might be a plasmablastic plasmacytoma, a CD138 immunostain was performed and was diffusely positive. CD56 was also positive in 50% of the plasma cells (Figures 1c, 1d). CD31 had membranous staining of cells. It has been shown that about 50% of plasmacytomas will express CD31 (6). In situ hybridization showed lambda restriction (Figure 1e, 1f). The lymph nodes showed follicular hyperplasia and the presence of polyclonal plasma cells in the sinusoids. There was no evidence of carcinoma by pancytokeratin immunostain. The patient returned to establish care with her oncologist in December 2016. She underwent a bone marrow biopsy and aspirate that showed no evidence of a plasma cell dyscrasia.

Figure 1.

(a) Solid mass of atypical plasma cells measuring 8.8 cm in greatest dimension. (b) Atypical cells with enlarged, eccentric nuclei and prominent nucleoli. There is background eosinophilic stroma. (c) CD138 immunostain is diffusely positive for plasma cells. (d) CD56 is positive in 50% of the plasma cells. (e) Kappa in situ hybridization is negative in plasma cells. (f) Lambda in situ hybridization is 100% positive in plasma cells.

DISCUSSION

Primary breast plasmacytomas are not common. Approximately 45 cases of breast plasmacytoma have been published in the literature since 1928 (7). The prevalence of breast plasmacytomas at one institution (out of all identified plasmacytomas) was reported at 1.5% (1). Both primary and secondary plasmacytomas can be misdiagnosed as primary breast carcinoma or even a benign process. Clinically, the majority of cases occur in women with a mean age of 53 years (3). Patients present with a palpable breast mass. Skin thickening and inflammatory signs may occur and suggest a breast abscess or inflammatory carcinoma. Patients have no clinical or imaging features of multiple myeloma. There is an absence of hypercalcemia, renal insufficiency, anemia, and lytic bone lesions. About 20% of patients have a small M-protein, most commonly IgA. Serum or urinary paraprotein levels are <2 g/dL (1).

These neoplasms are usually cured with local radiation therapy and/or chemotherapy; however, regional recurrences can occur in up to 25% of patients (5). Metastasis to distant extramedullary sites is not uncommon, and 30% to 50% of patients may progress to multiple myeloma with a median time of 1.5 to 2.5 years (1). Conversely, plasmacytomas may be secondary to disseminated multiple myeloma. In a study by Surov et al, 8 of 53 patients (15%) presented with a primary breast plasmacytoma, and the remaining 45 patients (85%) had secondary breast plasmacytoma from spread of multiple myeloma (2). It may be prudent, therefore, to perform bone marrow biopsy and laboratory testing, such as serum and urine protein electrophoresis and immunofixation, in patients who are diagnosed with breast plasmacytoma to rule out multiple myeloma. Primary breast plasmacytomas have a better prognosis than secondary involvement of the breast by multiple myeloma (2). After successful treatment of the tumor, 70% of patients remain disease free at 10 years (5).

The reported incidence of plasmablastic breast plasmacytomas is very rare. Given the patient's history of multiple myeloma, the presence of an extramedullary plasmacytoma could be a manifestation of recurrent multiple myeloma or an independent, primary process. The nature of the original myeloma as to light chain restriction could not be obtained. Clinically and microscopically, plasmacytomas can mimic other processes, both benign and malignant, as in this case. It is important for clinicians and pathologists to be knowledgeable about this entity to ensure correct diagnosis and therapy.