AJR 2004; 183:1779-1781
© American Roentgen Ray Society
MRI Appearance of Accessory Breast Tissue: A Diagnostic Consideration for an Axillary Mass in a Peripubertal or Pubertal Girl
Tal Laor1,
Margaret H. Collins2,
Kathleen H. Emery1,
Lane F. Donnelly1,
Kevin E. Bove2 and
Edgar T. Ballard2
1 Department of Radiology, Cincinnati Children's Hospital Medical Center and
University of Cincinnati College of Medicine, 3333 Burnet Ave., Cincinnati, OH
45229-3039.
2 Department of Pathology, Cincinnati Children's Hospital Medical Center and
University of Cincinnati College of Medicine, Cincinnati, OH.
Received January 9, 2004;
accepted after revision March 16, 2004.
Address correspondence to T. Laor.
Abstract
OBJECTIVE. The purpose of this study was to describe the MRI
appearance of accessory breast tissue that should be considered a diagnostic
possibility in peripubertal or pubertal girls who present with an axillary
mass along the course of the primitive milk streak.
CONCLUSION. The MRI appearance of accessory breast tissue is of a
mass discontinuous with—but with signal intensity and contrast
enhancement characteristics similar to—normal breast parenchyma.
Introduction
Accessory breast tissue is residual tissue that persists from normal
embryologic development, found in 2–6% of women
[1]. During the fifth week of
embryologic development, an ectodermal primitive milk streak forms along the
ventral surface of the body extending from the axilla to the inguinal region
[2]. From this streak, a
mammary ridge develops in the thorax, although the remaining streak regresses.
Further differentiation into complete breast parenchyma occurs during the
remainder of gestation. Incomplete involution anywhere along the primitive
milk streak can result in accessory or ectopic breast tissue. This tissue
ranges from a small focus of parenchyma to complete structures that include a
nipple and areola [3]. In a
young child, the accessory tissue usually is not identified because the mass
is small. During menarche, the mass may enlarge and become symptomatic,
causing the child to seek medical attention. Symptoms generally increase in
response to normal hormonal stimulation. In this article, we describe the MRI
appearance of accessory breast tissue that presented as a palpable mass in the
axilla of peripubertal or pubertal girls.
Materials and Methods
We encountered several cases in which a palpable mass within the axilla of
peripubertal or pubertal girls was evaluated using MRI and proven to be
accessory breast tissue at surgery. As a result, we searched a computerized
database (from 1971 to present) in the Department of Pathology for the
diagnosis of accessory breast tissue. The radiology records from children with
this diagnosis were examined to determine who had undergone MRI as part of the
clinical evaluation for a palpable mass within the axilla. The MRI
examinations were reviewed to evaluate the signal characteristics, the
enhancement pattern, and the configuration of the palpable mass. Because the
MRI examinations were performed over several years, the imaging sequences
varied, but each study included a conventional spin-echo T1-weighted, a fast
spin-echo T2-weighted, and a conventional fat-suppressed spin-echo T1-weighted
sequence after IV contrast administration. Medical records and pathology
slides from the children with MRI examinations also were reviewed.
Institutional review board approval for this retrospective study was obtained.
Informed consent was not required. Information was recorded in a secure,
de-identified database.
Results
Sixteen girls (age range, 9–17 years; mean age, 13.8 years) who
underwent surgical excision and had a subsequent diagnosis of accessory breast
tissue over a period of 32 years were identified. Between 1998 and 2003, four
of these girls underwent MRI of a palpable mass in the axilla. Each of these
girls presented with a mass that slowly enlarged over 1–1.5 years and
was tender to palpation. Three masses were left-sided and one was right-sided.
Two girls underwent sonographic evaluation initially for presumptive diagnoses
of lymphatic malformation and lymphadenopathy
(Fig. 1A). Three girls were
treated with antibiotics for presumed infection (one for possible cat-scratch
disease), but none improved.
In all four girls, MRI at 1.5 T showed a poorly demarcated mass confined to
the subcutaneous tissues of the axilla. The masses showed heterogeneous signal
intensity composed of hyperintense and hypointense tissue on T1-weighted
images (Fig. 2A).
Fat-suppressed fast spin-echo T2-weighted images were characterized by
moderately hyperintense parenchyma with interspersed regions of signal
intensity consistent with fat (Fig.
3). The amount of fat signal within the mass compared with the
adjacent breast was variable. All masses showed moderate enhancement after IV
contrast administration on fat-suppressed T1-weighted images, similar to the
ipsilateral breast parenchyma (Fig.
1B). Each mass was separate from normal breast tissue. One girl
had normal-appearing lymph nodes in the ipsilateral axilla. After MRI, no
definitive diagnosis was made because the appearance was considered
nonspecific, and all girls subsequently underwent surgery.
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Fig. 2A —12-year-old girl with axillary mass. Coronal T1-weighted MR
image (TR/TE, 400/14) of right axilla shows poorly defined mass
(arrow) of heterogeneous signal intensity. Inferior part of mass is
hyperintense, consistent with fat.
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Fig. 3. —Axial fat-suppressed T2-weighted MR image (TR/TE, 3,500/85)
of left axilla in 16-year-old girl with her arm raised over her head shows
superficial band-like mass of increased signal intensity (arrow) with
interspersed suppressed fat signal.
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Fig. 1B. —15-year-old girl with axillary mass. Axial fat-suppressed
T1-weighted MR image (TR/TE, 600/22) after IV contrast administration shows
mild enhancement of left axillary mass (arrow). Signal intensity
corresponding to fat is more abundant in mass than in ipsilateral breast. Note
that mass is not contiguous with normal, enhancing breast tissue
(asterisk).
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Pathologic evaluation of the mass in three girls showed benign mammary
tissue composed of lobules and ducts embedded in a fibrous stroma, admixed
with mature adipose tissue (Fig.
2B). One specimen had no breast lobules and only a few ducts but
abundant adipose and fibrous tissue.
Discussion
The differential diagnosis of an axillary mass in a peripubertal or
pubertal girl includes a lipoma
[4], lymphadenopathy or
lymphadenitis, hidradenitis
[5], sebaceous cyst, vascular
malformation, and malignancy
[6]. We have found that
accessory breast tissue also may be a cause of an axillary mass in a
peripubertal or pubertal girl and should be included in the differential
diagnosis.
Accessory breast tissue can present as a mass anywhere along the course of
the embryologic mammary streak but is most frequently found in the axilla
[7]. The vulva is the next most
common site for ectopic breast tissue
[8]. The mass may be composed
of glandular breast tissue, a nipple complex, or both
[4,
6]. Accessory breast tissue
also may be bilateral [9].
Accessory breast tissue responds to hormonal stimulation and may become more
evident during menarche, pregnancy, or lactation. Discomfort, pain, milk
secretion, and local skin irritation can occur
[5].
Both benign and malignant diseases of breast tissue in ectopic locations in
adult women have been described
[5]. Various disorders
associated with supernumerary nipples, including urogenital defects, vertebral
abnormalities, pyloric stenosis, testicular carcinoma, and aberrant
ventricular conduction [6,
8] have been reported.
Screening for renal anomalies in patients with accessory breast tissue remains
controversial [10]. The
treatment of choice for symptomatic accessory axillary breast tissue is
surgical excision [2,
5,
11]. Removal of the tissue
will relieve physical discomfort and confirms the diagnosis
[5].
Accessory breast tissue in the axilla resembles normal glandular parenchyma
on mammography [9]. It is
separate from the breast, unlike the axillary tail of Spence, which is a
normal direct extension toward the axilla from the main breast tissue
[9]. Although the imaging
findings are not specific, sonography can show the increased echotexture of
normal breast tissue [2,
12]. Cystic or adenomatous
changes in the ectopic mass may also be evident on imaging
[12].
MRI of soft-tissue masses is widely used in children. It can be used to
delineate the extent of the lesion and monitor therapy. Although many lesions
have characteristic appearances on MRI, many have features that are
nonspecific and thus require tissue sampling for diagnosis. In our patients,
the palpable masses were referred for MRI to define signal characteristics and
extent of lesion. All the girls' MRI examinations showed signal
characteristics similar to the adjacent, noncontiguous breast tissue, although
the amount of interspersed fat was variable. The masses were poorly
demarcated. IV contrast enhancement was heterogeneous, similar to breast
parenchyma. The preoperative diagnosis of ectopic breast tissue was suggested
by the imaging findings in two of the four girls who had undergone surgical
excision. Although accessory axillary breast tissue is relatively uncommon as
a clinical problem (in our series, less than one case per year), this
possibility should be entertained when the imaging appearance, although
nonspecific, resembles normal breast parenchyma. This may decrease the use of
unnecessary antibiotics and alleviate anxiety until surgical management.
In conclusion, accessory breast tissue should be considered a diagnostic
possibility in peripubertal or pubertal girls who present with an axillary
mass along the course of the primitive milk streak. The MRI appearance is of a
subcutaneous poorly demarcated mass discontinuous with—but having signal
intensity and contrast enhancement characteristics similar to—normal
breast tissue. Surgical resection for symptomatic relief is the treatment of
choice.
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Abstract
Introduction
