ANATOMIC PATHOLOGY
Original Article
Mucocele-like Tumors of the Breast
Cytologic Findings in Two Cases
VIVEK BHARGAVA, M.D., THEODORE R. MILLER, M.D., AND MICHAEL B. COHEN, M.D.
Mucocele-like tumors of the breast originally were reported by
Rosen in 1986 as benign lesions that histologically resembled
colloid carcinoma of the breast. The authors document two cases
of mucocele-like tumors to illustrate the difficulty in separating
these lesions from colloid carcinoma on the basis of fine-needle
aspiration biopsy. Cytologically, mucocele-like tumors contained
abundant mucin, few clusters, and sheets of regular epithelium
that lacked nuclear atypia, and they contained no intact single
cells. The authors recommend open surgical biopsy when fineneedle aspiration biopsy findings in such cases are equivocal.
(Key words: Breast; Fine-needle aspiration biopsy; Colloid carcinoma; Mucocele; Cytology) Am J Clin Pathol 1991;95:
875-877
Mucocele-like tumors (MLTs) of the breast were first described by Rosen, who likened them to mucoceles of minor salivary glands.' In five of the six cases he described
in his study, the lesions produced a mass. Biopsy specimens revealed features that closely resembled those of
colloid carcinoma. More recently, Ro and associates described six additional cases of MLT, all of which likewise
presented with a mass.2 All of the patients described by
Ro and associates had MLTs associated with a microscopic focus of colloid carcinoma or atypical ductal hyperplasia, suggesting that patients with these lesions should
have close clinical follow-up. The following report focuses
on the cytologic features of MLTs of the breast, and discusses the difficulty in distinguishing them from colloid
carcinoma on the basis of fine-needle aspiration biopsy
(FNAB) specimens.
Case 2
A 29-year-old woman presented with bilateral, firm, mobile breast
masses (2 cm and 0.5 cm in diameter). FNABs of both lesions contained
large amounts of mucinous material. An open surgical biopsy subsequently was performed on therightside. This yielded a yellow-tan piece
offibroadiposetissue measuring 3.0 cm in greatest dimension.
MICROSCOPIC FINDINGS
The cytologic findings in the FNAB smears were identical in both cases. On Papanicolaou (Pap) -stained
smears, there was abundant mucinous material that was
stained yellow-green. Amidst this background, there were
variably sized, monolayered sheets of epithelial cells with
nuclei of uniform size and shape (Figs. 1 and 2). No nucleoli were present. A few naked nuclei and rare single
cells with intact cytoplasm were admixed with the mucin.
REPORT OF TWO CASES
On May-Griinwald-Giemsa (MGG) -stained smears, the
mucinous material was stained blue-purple. Sheets of epCase 1
ithelial cells were seen with features similar to those in
A 38-year-old woman presented with an asymptomatic, 1-cm, cirthe Pap-stained smears. Because colloid carcinoma could
cumscribed mass in the right breast. An FNAB was performed that yielded
not be excluded diagnostically, a recommendation for
mucinous material. An open biopsy subsequently was performed. The
open
surgical biopsy was made in both cases.
biopsy specimen consisted of a yellow-tan,fibrofatty,lobular mass meaThe surgical specimens from the two cases showed hissuring 2 cm in greatest dimension.
tologically similar features. Dilated cysts were noted, with
mucinous material in a fibrous stroma (Fig. 3). The cysts
From the Department of Pathology, University of California. San
were
partially lined by cuboidal to columnar epithelium.
Francisco, California.
Nuclei showed mild variation in size and shape, and nuReceived June 20, 1990; received revised manuscript and accepted
cleoli were inconspicuous. Focal areas of epithelial hyfor publication September 24, 1990.
perplasia were noted, without atypia. The microscopic
Address reprint requests to Dr. Cohen: Department of Pathology, 5216
features were compatible with those of MLT of the breast.
RCP, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242.
875
876
ANATOMIC PATHOLOGY
Original Article
FlG. 1 {upper, left). Amidst a background of mucin is a
large, monolayered sheet of benign epithelium and scattered mononuclear inflammatory cells. Papanicolaou
(X40).
FIG. 2 (lower, left). A monolayered sheet of benign breast
epithelium with mucin in the background. May-GriinwaldGiemsa (X250).
FIG. 3 (upper, right). Mucocele-like tumor of the breast.
Cystic spaces, partially lined by epithelium, with extravasation of mucin (X40).
DISCUSSION
Although the histologic similarities between colloid
carcinoma of the breast and MLT of the breast have been
described previously,''2 our report is the first (to our
knowledge) to focus on the difficulty in distinguishing between these lesions in FNAB specimens. The cytologic
findings in our two cases could not be used to exclude a
diagnosis of colloid carcinoma. Only on the basis of open
surgical biopsies was the definitive interpretation of MLT
possible.
In the review of 42 cases of colloid carcinoma by Silverberg and associates, women with this neoplasm were
older than those with a second component of infiltrating
ductal carcinoma (mean age: 68.6 years for pure colloid
carcinoma; 51.4 years for mixed colloid carcinoma). In
addition, they had a longer duration of symptoms and
presented with larger masses.3 The patients with MLTs
A.J.C.P.-June 1991
877
BHARGAVA, MILLER, AND COHEN
Mucocele-like Tumors of the Breast
that have been reported in the literature were considerably
younger than those with colloid carcinoma. The six patients reported in Rosen's series averaged 40 years of age;
those in Ro's study presented at a mean age of 50 years.1'2
Thus, a diagnosis of colloid carcinoma in younger women
seems relatively unlikely, and only should be made with
caution.
Several studies have compared the cytologic findings
in colloid carcinoma of the breast with those of other
breast lesions, including pregnancy change, fibroadenoma,
lobular carcinoma, ductal carcinoma, and medullary carcinoma.4,5 The authors of these reports have emphasized
the benign-appearing cytologic appearance of many colloid carcinomas. In a study by Duane and associates, the
key morphologic features of colloid carcinoma were dense
cellularity, single cells in a mucinous background, nuclear
eccentricity, and minimal nuclear atypia.4 Stanley and
associates studied the cytologic features of 9 colloid carcinomas and 13 mixed colloid-infiltrating ductal carcinomas.5 They found the FNAB features of colloid carcinoma to include abundant extracellular mucin, three-dimensional cell groups with smooth borders, and uniform
nuclei with rare nucleoli. It is apparent from these studies,
as well as our own, that the absence of nuclear atypia does
not exclude a diagnosis of colloid carcinoma.
Cystic hypersecretory duct carcinoma is a recently described, rare variant of intraductal carcinoma, which may
be confused with MLT.67 From the single case report
describing the cytologic findings of the former lesion, it
appears that the cystic contents are most useful in separating these two entities.6 In MLT, true mucin is present;
the fluid component of cystic hypersecretory duct carcinoma has a striking resemblance to colloid in the thyroid
gland. In both of these lesions, the epithelium lacks significant atypia.
. We would like to emphasize that, given the above cytologic features, MLTs of the breast must be considered
in the differential diagnosis of a mucin-containing FNAB
specimen from the breast that also shows benign-appear-
TABLE 1. CYTOLOGIC FEATURES USEFUL TO DISTINGUISH
MUCOCELE-LIKE TUMOR (MLT) FROM
COLLOID CARCINOMA
Mucocele-like Tumor
Colloid Carcinoma
Scant cellularity
Abundant mucin
Regular cohesive sheets
No intact single cells
Bland nuclei
Cellularity
Abundant mucin
Irregular cohesive sheets
Intact single cells
Coarse, irregular nuclei
ing epithelium. There are some cytologic features that
may be useful in distinguishing MLT from colloid carcinoma (Table 1). In MLT, the epithelium in FNAB
smears is relatively scanty, and it is arranged in cohesive
monolayered sheets. Smears from colloid carcinoma are
usually cellular, they contain irregular sheets of epithelium
and numerous cells with intact cytoplasm. Without conclusive cytologic evidence of malignancy, we recommend
deferring the diagnosis and suggest an open biopsy (especially in younger women) because of the potential overlap in the cytomorphologic characteristics of these lesions.
REFERENCES
1. Rosen PP. Mucocele-like tumors of the breast. Am J Surg Pathol
1986;10:464-469.
2. Ro J, Sahin A, Sneige N, Silva E, Ayala A. Mucocele-like tumor
(MLT) of the breast: a clinicopathologic study of 6 cases. Lab
Invest 1990;62:83A.
3. Silverberg SG, Kay S, Chitale AR, Levitt SH. Colloid carcinoma of
the breast. Am J Clin Pathol 1971;55:355-363.
4. Duane GB, Kanter MH, Branigan T, Chang C. A morphologic and
morphometric study of cells from colloid carcinoma of the breast
obtained by fine needle aspiration. Distinction from other breast
lesions. Acta Cytol (Baltimore) 1987;31:742-750.
5. Stanley MW, Tani EM, Skoog L. Mucinous breast carcinoma and
mixed mucinous-infiltrating ductal carcinoma: a comparative
cytologic study. Diagn Cytopathol 1989;5:134-138.
6. Colandrea JM, Shmookler BM, O'Dowd GJ, Cohen MH. Cystic
hypersecretory duct carcinoma of the breast. Report of a case
with fine-needle aspiration. Arch Pathol Lab Med 1988; 112:560563.
7. Rosen PP, Scott M. Cystic hypersecretory duct carcinoma of the
breast. Am J Surg Pathol 1984;8:31-41.
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