Pleomorphic adenoma of the breast: A case report and distinction from mucinous carcinoma

Archives of Pathology & Laboratory Medicine,  Apr 2003  by Reid-Nicholson, M,  Bleiweiss, I,  Pace, B,  Azueta, V,  Jaffer, S

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Pleomorphic adenoma of the breast is a rare, benign tumor accounting for 68 cases in the literature. It is most commonly seen in postmenopausal women and is characterized by an admixture of epithelial and myoepithelial cells embedded in abundant myxomatous stroma. Its clinical and histologic appearance can be challenging and may lead to a misdiagnosis of invasive carcinoma. We report a case of mammary pleomorphic adenoma in an asymptomatic 59-year-old woman and briefly discuss its distinction from mucinous carcinoma through the use of special stains.

Pleomorphic adenoma (PA), also known as benign mixed tumor, accounts for 45% to 74% of all major and minor salivary gland tumors and has been reported in other, less common sites such as the paranasal sinuses, larynx, palate, and nasal septum.1 It also occurs in the skin, where it is more commonly known as chondroid syringoma. It occurs less frequently in the human breast, however. Since the first case report by Lecene2 in 1906, 68 cases of PA of the human breast (PAB) have been documented in the world literature. This is not surprising given that the breast is a modified sweat gland1 that shares with its skin and salivary gland counterparts an embryologic origin from the same ectodermal layer.

REPORT OF A CASE

A 59-year-old, gravida 7, para 5 woman with a history of hypertension, obesity, peptic ulcer, and gastroesophageal disease discovered a mass in her right breast 10 years ago. The mass was described as firm in consistency; it measured 2 cm in maximum dimension and was located in the upper outer quadrant. It was clinically followed by serial mammograms without significant change until a recent mammogram showed a slight increase in its size (Figure 1). No calcifications were noted. Clinical examination confirmed an increase in the size of the lesion; however, there was no nipple retraction or discharge. The mass was completely excised. The patient tolerated the procedure and is currently in good health.

MATERIALS AND METHODS

Routine hematoxylin-eosin sections were prepared from formalin-fixed, paraffin-embedded tissue. Immunohistochemical studies were performed by indirect staining methods using antibodies against cytokeratin (CAM 5.2, 1:4, Becton Dickinson, La Brea, Calif), vimentin (V9, no dilution, Dako Corporation, Carpinteria, Calif), muscle-specific actin (HHF35, 1:6, Enzo, Farmingdale, NY), S100 (polyclonal, 1:6000, Dako), desmin (clone 33, 1:5, BioGenex, San Ramon, Calif), and glial fibrillary acidic protein (6F2, 1:2000, Dako).

PATHOLOGIC FINDINGS

The excised portion of breast tissue measured 2.5 x 2.0 x 1.2 cm and, on sectioning, showed a circumscribed 0.9cm gray-yellow mass with a 0.2-cm hemorrhagic focus. Histologic examination showed a circumscribed neoplasm (Figure 2) surrounded by fatty breast tissue. The cellular composition of the neoplasm consisted of epithelial, stellate, and spindle cells in pale blue myxoid stroma (Figure 3). The epithelial component showed tubules and cords of cuboidal cells with pink cytoplasm and small oval nuclei (Figure 4). Stellate and spindle-shaped myoepithelial-type cells were seen in the stroma. An intraductal papilloma with areas of florid duct hyperplasia was also identified immediately adjacent to the neoplasm. The papilloma was composed of a mixture of proliferating ductal cells and darker-staining, spindle-shaped myoepithelial cells (Figure 5). No chondroid metaplasia was evident. The myxoid areas stained positively with mucicarmine and alcian blue (at pH 1.0 and 2.5). Alcian blue staining was obliterated by hyaluronidase pretreatment (at pH 1.0 and pH 2.5). The myoepithelial-type cells stained positively with S100 protein, vimentin, muscle-specific actin (Figure 6), and cytokeratin (CAM 5.2) and were negative for desmin and glial fibrillary acidic protein. Epithelial cells stained strongly with cytokeratin only. The histologic appearance and immunohistochemical findings were consistent with a PAB.

COMMENT

A benign mixed tumor of the breast (PAB) is an uncommon neoplasm, accounting for 68 cases in the literature. It is a circumscribed lesion characterized by a mixture of epithelial and myoepithelial cells embedded in abundant stroma, which may be composed of 1 or more of the following matrices: (1) myxoid, (2) chondroid, or (3) osseous. PAB was first reported in 1906 by Lecene,2 who described a case with cartilaginous and osseous metaplasia. Women are more commonly affected (female-male ratio >10:1) than men, and patients can range in age from 23 to 78 years (mean, 61 years). Tumors range from 0.7 to 20 cm in diameter3 and are most commonly located in the periareolar area3 or upper outer quadrant.

On palpation, PAB is described as being firm to hard and well circumscribed. Dimpling of the overlying skin and nipple retraction are uncommon features that may arouse suspicion of malignancy. On mammography, tumors appear circumscribed and homogeneous (Figure 1), with dense or speckled calcification.4 Lesions with irregular infiltrative edges have also been reported.4