DOI:10.2214/AJR.04.0925
AJR 2005; 185:1310-1316
© American Roentgen Ray Society
Benign and Malignant Mucocele-Like Tumors of the Breast: Mammographic and Sonographic Appearances
Ji-Young Kim1,2,
Boo-Kyung Han1,
Yeon Hyeon Choe1 and
Young-Hyeh Ko3
1 Department of Radiology and Center for Imaging Science, Samsung Medical
Center, Sungkyunkwan University School of Medicine, 50, Ilwon-Dong,
Kangnam-Ku, Seoul 135-710, South Korea.
2 Present address: Department of Radiology, Sanggye Paik Hospital, Inje
University College of Medicine, Seoul 139-707, South Korea.
3 Depatment of Pathology, Samsung Medical Center, Sungkyunkwan University School
of Medicine, Seoul 135-710, South Korea.
Received June 11, 2004;
accepted after revision November 29, 2004.
Address correspondence to B.-K. Han.
Abstract
OBJECTIVE. The purpose of this study was to analyze and compare the
mammographic and sonographic appearances of benign and malignant mucocele-like
tumors.
CONCLUSION. The mammographic appearance of mucocele-like tumor of
the breast is characterized as pleomorphic calcifications, often increasing in
number. Microcalcifications in malignant mucocele-like tumors extended over a
wider area than those in benign mucocele-like tumors. Sonography often shows
cysts with calcified or noncalcified mural nodules.
Introduction
Mucocele-like tumor of the breast is a rare lesion, pathologically
characterized as mucin-filled cysts and extravasated mucin presented in the
adjacent stroma [1]. Although
the first report of Rosen [1]
described this lesion as a benign entity, mucocele-like tumor has been
considered as a spectrum of pathologic lesions, including benign tumor,
atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS), and
mucinous carcinoma
[2-7].
Although several studies about the clinical and pathologic findings of
mucocele-like tumor have been reported
[1-3,
8,
9], only a few studies have
been published about the radiologic findings of mucocele-like tumor
[2,
4,
10,
11]. We analyzed and compared
mammographic and sonographic appearances of benign and malignant mucocele-like
tumors of the breast.
Materials and Methods
Between January 1998 and August 2002 at our institution, 25 lesions in 23
women were histologically proven to be mucocele-like tumors. Of the 25
lesions, 15 were benign mucocele-like tumors, including two lesions associated
with ADH, and 10 were malignant mucocele-like tumors, including nine with DCIS
and one with mucinous carcinoma. A breast-dedicated pathologist confirmed the
pathologic diagnoses after reviewing the pathologic slides. Medical records
were reviewed to determine the clinical manifestations.
All patients underwent mammography in two views (mediolateral oblique and
craniocaudal projections), seven had mammography at an additional
magnification, and 18 underwent additional sonography. Fifteen lesions had
imaging-guided large core needle biopsies (11, stereotactic; four,
sonographic), and 19 lesions including nine with core biopsies were surgically
excised.
We retrospectively analyzed the mammographic appearances according to the
BI-RADS lexicon [12]. The
assessment category on the original report was recorded. We also evaluated
sonographic findings.
Results
The clinical manifestations including laterality of the mucocele-like
tumors are described in Table
1. All 15 benign mucocele-like tumors were nonpalpable and were
detected on screening mammography. Three of 10 malignant mucocele-like tumors
were palpable, one presented with bloody discharge, one was incidentally found
adjacent to a palpable intraductal papilloma, and the remaining five were
detected on screening mammography. Four patients with malignant mucocele-like
tumors had a history of false-negative biopsy (one, excisional biopsy; one,
core needle biopsy; two, fine-needle aspiration) 6 months to 2 years earlier.
Four patients with benign mucocele-like tumors had a history of breast cancer
in the contralateral or ip-silateral breast. Of two bilateral lesions, one was
bilateral benign mucocele-like tumor and the other was bilateral malignant
mucocele-like tumor. The patients ranged in age from 27 to 55 years, and the
mean age of the patients with malignant mucocele-like tumors (37.2 years) was
younger than that in the patients with benign mucocele-like tumors (41.4
years) (p < 0.05).
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Fig. 1C —41-year-old woman with benign mucocele-like tumor of breast.
Photomicrograph shows thick-walled cyst with mucin extruded into surrounding
stroma. Calcifications are not evident due to loss during preparation.
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At mammography, all 25 mucocele-like tumors showed calcifications (Figs.
1A,
1B,
1C,
2A,
2B,
3A,
3B,
3C,
4,
5A,
5B,
5C,
6A,
6B, and
6C), and five (20%) (two,
benign; three, malignant) appeared as a single round mass or multiple
rosarylike masses (Figs. 3A,
3B,
3C,
4,
5A,
5B, and
5C). The shape of the
calcifications was pleomorphic in 11 (73%) of 15 benign and in eight (80%) of
10 malignant mucocele-like tumors. The calcifications were often mixed with
large coarse eggshell-shaped calcifications or with fine linear calcifications
(Figs. 1A,
1B,
1C,
2A,
2B,
3A,
3B,
3C,
4,
5A,
5B,
5C,
6A,
6B, and
6C); however, branching linear
calcifications were absent.
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Fig. 2A —29-year-old woman with bilateral malignant mucocele-like
tumor who presented with palpable mass in right breast. Bilateral mediolateral
oblique mammogram shows pleomorphic calcifications mixed with large coarse
eggshell-shaped calcifications in diffuse distribution extending over a wide
area. Definite mass shadow is not seen.
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Fig. 2B —29-year-old woman with bilateral malignant mucocele-like
tumor who presented with palpable mass in right breast. Photograph of surgical
specimen shows multiple mucin-filled cysts. Bilateral mucocele-like tumor with
ductal carcinoma in situ was confirmed at surgery.
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Fig. 3A —36-year-old asymptomatic woman with benign mucocele-like
tumor and recurrence after removal of calcifications 7 months ago. Mammogram
shows multiple separate round calcific clusters. Sonography (not shown)
revealed only calcification without mass or cyst. Patient underwent excisional
biopsy after needle localization for largest calcific cluster
(arrows), and on postoperative mammography (not shown), cluster had
disappeared.
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Fig. 3B —36-year-old asymptomatic woman with benign mucocele-like
tumor and recurrence after removal of calcifications 7 months ago.
Photomicrograph shows extravasated mucin with dense calcifications and mild
ductal hyperplasia. (H and E, original magnification, x12.5)
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Fig. 3C —36-year-old asymptomatic woman with benign mucocele-like
tumor and recurrence after removal of calcifications 7 months ago. Mammogram
obtained 7 months after A and B shows new calcific clusters
(arrow) have also developed in other region of same breast.
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Fig. 4 —55-year-old woman with benign mucocele-like tumor and known
contralateral breast cancer. Screening mammogram shows pleomorphic
calcifications with multiple clusters associated with well-defined nodular
densities (arrows). Number of calcifications showed increasing
pattern since previous screening mammogram (not shown).
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Fig. 5A —40-year-old woman with malignant mucocele-like tumor of left
breast. Screening mammogram shows multiple pleomorphic calcific clusters with
segmental distribution associated with multiple rosarylike masses
(arrows).
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Fig. 5C —40-year-old woman with malignant mucocele-like tumor of left
breast. Four photomicrographs from one specimen show mucin in cysts (left
upper image), mucin extruded from cysts (right upper image),
mucin with calcifications within lobules (left lower image), and
mucinous carcinoma (right lower image), represented as floating
carcinoma cells in mucin. Mucocele-like tumor with mucinous carcinoma is
proven. (H and E, original magnification, x12.5, x40)
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Fig. 6A —44-year-old woman with malignant mucocele-like tumor who
presented with palpable mass in right breast. Mammogram shows segmentally
distributed pleomorphic microcalcifications with ill-defined increased opacity
(arrows).
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Fig. 6B —44-year-old woman with malignant mucocele-like tumor who
presented with palpable mass in right breast. Sonogram shows conglomerated
multiple small cysts with internal calcifications (arrows).
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Fig. 6C —44-year-old woman with malignant mucocele-like tumor who
presented with palpable mass in right breast. Photomicrographs show
mucin-filled epithelium-lined cysts with extravasated mucin in stroma
(left image) and micropapillary-type ductal carcinoma in situ
associated with mucocele-like tumor (right image). (H and E, original
magnification, x12.5, x40)
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The distribution of calcifications was clustered in 13 (87%) of 15 benign
mucocele-like tumors and in two (22%) of nine malignant mucocele-like tumors,
and segmental or diffuse distribution was identified only in malignant
mucocele-like tumors—not in any of the benign mucocele-like tumors
(Figs. 1A,
1B,
1C,
2A, and
2B). The median extent of the
calcifications, when measurable, was 0.8 cm (range, 0.5-4.0 cm) for benign
mucocele-like tumors and 5.7 cm (range, 1.0-8.0 cm) for malignant
mucocele-like tumors. In three mucocele-like tumors, multiple round calcific
clusters, separated or connected like a rosary, were identified (Figs.
3A,
3B,
3C,
4,
5A,
5B, and
5C). Therefore, 11 of 15
benign mucocele-like tumors and eight of 10 malignant mucocele-like tumors
were assessed as low to intermediate concern for malignancy, among lesions in
BI-RADS category 4.
Three patients with mucocele-like tumors showing scattered calcifications
on mammography underwent surgery due to sonographic or palpable abnormality.
Six mucocele-like tumors (four, benign; two, malignant) showed punctate or
radiolucent-centered calcifications. A benign mucocele-like tumor recurred
after complete removal of calcifications, and the final diagnosis was also
benign mucocele-like tumor (Figs.
3A,
3B, and
3C). Five benign mucocele-like
tumors showed an interval increase in the number of calcifications. The
details of the mammographic appearances of mucocele-like tumors are summarized
in Table 2.
At sonography, 10 cases showed a cyst or cysts with calcified (n =
7) or noncalcified (n = 3) mural nodules (Figs.
1A,
1B,
1C,
6A,
6B, and
6C), three cases showed
hypoechoic nodule with (n = 1) or without (n = 2)
calcification (Figs. 5A,
5B, and
5C), one case showed only
calcifications, and four did not show any sonographic abnormalities
(Table 3). Benign and malignant
mucocele-like tumors were similar on sonography.
In microscopic evaluation of the 15 benign mucocele-like tumors, 10 had
ductal hyperplasia: four had mild hyperplasia; four, atypical; and two,
micropapillary. The remaining five did not have ductal hyperplasia (Figs.
1A,
1B,
1C,
3A,
3B, and
3C). All 10 malignant
mucocele-like tumors had micropapillary DCIS, and one had an additional
mucinous carcinoma (Figs. 2A,
2B,
5A,
5B,
5C,
6A,
6B, and
6C). The results of core
biopsy in 11 benign mucocele-like tumors were benign mucocele-like tumor in
six, mucocele-like tumor with atypia in four, and fibrocystic change in one.
The results of core biopsy in four malignant mucocele-like tumors were benign
mucocele-like tumor, mucocele-like tumor with atypia, mucocele-like tumor with
DCIS, and fibrocystic change.
Six of 12 cases with benign mucocele-like tumor or mucocele-like tumor with
atypia diagnosed by core biopsy underwent surgical excision, and two (33%)
were associated with DCIS. Nineteen of 25 cases underwent surgery: excision in
16, mastectomy in three. There was no case with axillary lymph node
metastasis.
Discussion
Mucocele-like tumor of the breast is a rare disease that is characterized
by distended mucin-filled ducts or cysts lined by a benign two-cell layer
epithelium and rupture of these cysts, resulting in extrusion of secretions
and epithelium into the surrounding breast stroma. The pathogenesis of
mucocele-like tumor of the breast is uncertain. Rosen
[1] suggested that excess
production of mucin or ductal obstruction may be contributing factors and then
minor trauma is probably sufficient to cause rupture of distended cysts or
ducts and extravasation of the mucin. The gross pathologic findings have been
described as multicystic or multiloculated lesions.
Since the first report of mucocele-like tumor of the breast by Rosen
[1], subsequent studies have
confirmed the concept of a spectrum of pathologic lesions of mucocele-like
tumors, including benign lesions, ADH, DCIS, and mucinous carcinomas
[2,
4-8,
13]. Our study of 25 cases
included four mucocele-like tumors with ADH (16%), nine mucocele-like tumors
with DCIS (36%), and one mucocele-like tumor with mucinous carcinoma (4%).
Mucocele-like tumor with carcinoma is a low-grade neoplasm with few
clinical differences from benign mucocele-like tumor
[8,
11]. Fine-needle aspiration
cytology of benign mucocele-like tumor may be difficult to distinguish from
mucinous carcinoma. Excisional biopsy is required for an accurate diagnosis.
Surgical excision is recommended for benign mucocele-like tumor, and
breast-conserving surgery is appropriate therapy for mucocele-like tumor with
carcinoma. Axillary nodal metastasis of mucocele-like tumor has not been
reported [8,
11], and axillary lymph node
dissection may be unnecessary. Although our series included only one case of
invasive cancer, there was also no axillary nodal metastasis. Radiation
therapy is indicated if a carcinoma involves margins or if extensive
intraductal carcinoma is present
[2,
4-8,
11].
Although some reports have suggested that patients with benign
mucocele-like tumors are younger than patients with mucinous carcinomas
[1,
2,
11], in our study, patients
with malignant mucocele-like tumors were younger. We think that the shape of
calcifications with low to intermediate concern of malignancy could lead to
selection of different management plans for young and old patients. The
patients in the older age group are liable to accept biopsy due to the higher
likelihood of malignancy, so mucocele-like tumors can be detected
asymptomatically. Another reason patients with malignant mucocele-like tumors
were younger than those with benign tumors in our study is that the malignant
mucocele-like tumors of our study group were larger in extent and symptomatic
in 40%, so they could be detected in younger women more readily than benign
ones.
Different from previous pathologic reports
[1,
2,
8] in which mucocele-like tumor
presented with palpable mass, 22 of 25 mucocele-like tumors in our study were
nonpalpable. Because of the widespread use of screening mammography and the
development of less invasive biopsy procedures, such as core needle or
Mammotome (Ethicon Endo-Surgery) biopsy, many mucocele-like tumors in our
study were diagnosed in the nonpalpable state.
The description of mammographic appearances in patients with mucocele-like
tumors of the breast is limited to a few reports, and sonographic findings are
more poorly described. Recently, Glazebrook and Reynolds
[14] described the
mammographic appearances of mucocele-like tumors as indeterminate
microcalcifications or as a nodule, often containing calcifications.
Calcifications are the most frequent findings of mucocele-like tumor. On
pathologic examinations, the presence of large coarse microcalcifications
within the cysts and in the extravasated mucinous secretion is characteristic
[8].
In our patients, the most common mammographic appearance of mucocele-like
tumors was calcifications, seen in 19 of 25 cases assessed as BI-RADS category
4: 11, in benign mucocele-like tumors and eight, in malignant mucocele-like
tumors. The calcifications had pleomorphic shape, and the mixture of coarse
eggshell-shaped calcifications may suggest the presence of mucin-filled cysts.
In the malignant mucocele-like tumors, the calcifications extended over a
wider area than the calcifications in the benign mucocele-like tumors in our
series.
The sonographic appearance of mucocele-like tumors has been described in
few reports [14,
15]. Sonographic appearances
of cysts with calcified or noncalcified nodules, often multiple, may suggest
the diagnosis of mucocele-like tumor, but the appearance does not help to
differentiate between benign and malignant mucocele-like tumors.
All the malignant mucocele-like tumors combined with micropapillary DCIS.
Histologic underestimation of core biopsy was common, seen in three of four
malignant mucocele-like tumors. Three benign lesions, including one ADH, were
upgraded to DCIS in two and mucinous cancer in one.
In summary, the mammographic appearances of mucocele-like tumors of the
breast are characterized as pleomorphic, mixed with coarse or eggshell-shaped
calcifications that often increase in number and often are assessed as
low-grade BI-RADS category 4. Microcalcifications in malignant mucocele-like
tumors extend over a wider area than those in benign mucocele-like tumors.
Sonography often shows cysts with calcified or noncalcified mural nodules.
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Abstract
Introduction
