Breast

• Primary breast tumor with morphology similar to that of polymorphous low grade adenocarcinoma of the salivary glands
• "Low grade" terminology not used in these tumors due to reported case with widespread metastases

• Very rare tumor; only 3 reported cases, first described in 2006 (Virchows Arch 2006;448:29)
• Similar to tumors of the salivary glands; they are composed of monotonous cells arranged in nests and cords
• Difficult to know prognosis of such a rare tumor but shows slow, aggressive growth with metastatic potential

• The rare reported cases all presented as:
  • Palpable masses
  • 1.5 - 4 cm in greatest dimension (mean 3 cm) with infiltrative borders
  • Patient mean age 55 (range 37 - 74)
  • No axillary metastases reported but one patient developed distant metastases within 3 years

• All reported cases were treated with surgical resection (plus radiotherapy if breast conserving surgery) and axillary dissection

• Monotonous proliferation of neoplastic cells arranged in varying architectural patterns including tubules, trabeculae, alveolar, cribriform and solid nests
• Nuclei are round to ovoid with vesicular chromatin, moderate mitotic activity without necrosis
• Central and peripheral areas of the tumor may demonstrate differing architectural and immunohistochemical features

Contributed by Emily S. Reisenbichler, M.D.

• BCL2 (strong), CK7 (weak), E-cadherin (may be patchy), GFAP (focal), CK5 / 6

• ER, PR, HER2, AR, EMA, CD117

• Adenoid cystic carcinoma: both have cribriform and alveolar growth with possible basal lamina-like material and are triple negative (ER / PR / HER2)
  • Adenoid cystic carcinoma has two cell types with a population of actin positive cells that are absent in polymorphous adenocarcinoma
• Invasive lobular carcinoma: both can have single file pattern of growth but polymorphous adenocarcinoma has membranous E-cadherin and is negative for ER / PR and AR
• Salivary tumor metastatic to the breast: clinical history of a salivary neoplasm

• Semin Diagn Pathol 2010;27:77, Pathology 2017;49:215

What receptor profile is expected in a primary polymorphous adenocarcinoma of the breast?


1. ER+, PR+, HER2- (Luminal A)
2. ER-, PR-, HER2- (Basal-like)
3. ER-, PR-, HER2+ (HER2 positive)
4. ER+, PR+, HER2+

B. Like many of the salivary gland-like tumors of the breast, polymorphous adenocarcinoma is a triple negative, basal-like tumor. Unlike the poor prognosis seen in many triple negative breast tumors, salivary gland-like tumors, including polymorphous adenocarcinoma, may have a more favorable prognosis. (Appl Immunohistochem Mol Morphol 2013;21:283)

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Reference: Polymorphous carcinoma