Baylor University Medical Center Proceedings April 2017 - 203

Plasmablastic plasmacytoma of the breast
Don K. Le, DO, David Metter, MD, and John R. Krause, MD

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.

lasma 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.
Proc (Bayl Univ Med Cent) 2017;30(2):203-204

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
From the Department of Pathology, Baylor University Medical Center at Dallas, Texas.
Corresponding author: Don K. Le, DO, Department of Pathology, Baylor
University Medical Center at Dallas, 3500 Gaston Avenue, Dallas, TX 75246
(e-mail: don.le@bswhealth.org).
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