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1 March 2017 - Case of the Week #418

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Case of the Week #418

Clinical history:
A 68 year old woman presented with a breast mass, present for 14 years, but gradually increasing in size over the past 6 months. Clinical examination revealed a 10 cm mass with erythematous, indurated and shiny overlying skin and nipple retraction. Mammogram showed a lobulated breast measuring 8 x 7 cm, with no suspicious microcalcifications (BIRADS 4). FNA was positive for malignant cells. A modified radical mastectomy was performed, revealing a 6.5 x 5.0 cm grey white lobulated tumor with irregular borders, and yellow areas indicating necrosis. The overlying skin and nipple areola were grossly not involved by tumor.

Macro images:

Micro images:

Permission to use images courtesy of Indian J Pathol Microbiol 2011;54:230

What is your diagnosis?

Malignant Adenomyoepithelioma
No regional nodal metastasis (pT3N0)

Special Stains:





Smooth muscle myosin heavy chain

Test question (answer at the end):
Which of the following statements is not true:

A. Adenomyoepithelioma of the breast is a biphasic tumor.
B. Adenomyoepithelioma typically has benign or low grade malignant behavior.
C. It is considered a variant of intraductal papilloma.
D. In malignant cases, only the epithelial component demonstrates malignant transformation.


Histology shows a biphasic tumor of malignant myoepithelial and epithelial cells with cytologic atypia, mitotic figures and necrosis. Immunostains were positive in the epithelium for CK7, 34βE12 and CK5 (not shown), and in the myoepithelium for p63, smooth muscle myosin heavy chain and S100 (not shown). ER and PR were negative (not shown).

Adenomyoepithelioma, first recognized in the breast in 1970 (Curr Top Pathol 1970;53:161), is an uncommon biphasic tumor with variable epithelial and myoepithelial components, usually with benign to low grade malignant behavior and a propensity for recurrence (Arch Pathol Lab Med 2013;137:725). Since papillary formations are common, it is considered a variant of intraductal papilloma (Hum Pathol 1987;18:1232). Although rare, either component can show malignant transformation, so thorough examination is required. Malignant lesions have areas of classic tumor with either obvious or subtle focal malignant features. Recurrence and metastases have been reported in both groups (World J Surg Oncol 2013;11:285). The epithelial component is typically cytokeratin+, EMA+ and CEA+; the myoepithelial component is S100+, SMA+, SMMHC+ and p63+.

Other lesions with prominent myoepithelial cells include myoepitheliosis (non-palpable, microscopic proliferation of myoepithelial cells in or around small ducts) and myoepithelial carcinoma (no epithelial component).

Treatment includes surgery and standard chemotherapy or radiation therapy regimens. In one case report, eribulin was been reported to be effective (J Breast Cancer 2015;18:400).

Test Question Answer:
D. In malignant cases, both the epithelial and myoepithelial component may demonstrate malignant transformation.

Discussion by Nat Pernick, M.D.
Image 01 Image 02