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Case 454 - Discussion

Uploaded: 2010-10-27, Updated: 2011-03-09

 

Primary Adenoid Cystic Carcinoma of Breast

  • Rare, accounts for ~ 0.1% of all breast cancers.

  • Age: 60-70 years.

  • Mostly present as a palpable mass in the subareolar or central region of the breast without skin involvement.

  • Grossly usually circumscribed and nodular.

  • Histopathology

    • Dual population of epithelial cells and myoepithelial cells.

    • Epithelial cells: more abundant eosinophilic cytoplasm than the basaloid cells; may have glandular, squamous, and sebaceous differentiation.

    • Myoepithelial/basaloid cells: scant cytoplasm and hyperchromatic nuclei.

    • Architectural patterns: solid, cribriform, tubular, and trabecular configurations.

    • Both true lumens and pseudolumens are present. The true lumens are surrounded by CK7+ epithelial cells. The pseudolumens contain myxoid material or eosinophilic spherules composed of basement membrane components (type IV collagen and laminin) and are surrounded by myoepithelial/basaloid cells.

    • Associated DCIS with adenoid cystic features is seen in a minority of cases.

    • Adenoid cystic carcinoma may develop in a background of microglandular adenosis.

  • IPX:

    • Usually ER-, PR-, and lack of HER2 over expression.

    • CD117+

    • Myoepithelial/basaloid cells p63+

  • DDX:

    • Invasive cribriform carcinoma: a single epithelial cell population, lack of intraluminal basement membrane material, ER+, PR+.

    • Cribriform pattern DCIS: myoepithelial cells present but limited to the periphery.

    • Collagenous spherulosis: presence in both of myxoid material and eosinophilic spherules composed of basement membrane material. But collagenous spherulosis is not infiltrative and is confined to pre-existing ducts, lobules, or epithelial proliferative lesions.

    • The solid variant of adenoid cystic carcinoma has to be distinguished from high-grade invasive ductal carcinoma, small cell carcinoma, solid papillary carcinoma, and lymphoma. Identification of foci of basement membrane material and the demonstration of a dual epithelial-myoepithelial cell population by immunohistochemistry (IHC) will lead to the correct diagnosis

  • Prognosis: excellent with rarely axillary lymph node metastasis.