Breast-nonmalignant

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Breast-nonmalignant

Benign tumors / changes

Mucocele like lesion of breast

Reviewer: Hind Nassar, M.D. in January 2009 (see Authors page)

Revised: 8 October 2012, last major update April 2010

Definition

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● Mucin containing cysts that often rupture, with extravasation of mucin into surrounding stroma

● Cysts lined by flat epithelium without atypia

● Analogous to mucocele of minor salivary glands

Terminology

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Epidemiology

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● Mean age 40 years, range 25-61 years (Am J Surg Pathol 1986;10:464)

Sites

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Etiology

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Clinical features

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● Mucin extravasation or mucocele-like lesions at core biopsy warrant close radiological-pathological correlation and likely excision (Histopathology 2009;55:609)

● May be premalignant, associated with ADH or focal mucinous carcinoma

● Often appears malignant radiologically due to microcalcifications (Breast J 2005;11:15)

Prognostic factors

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Case reports

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● 43 year old woman with coexisting columnar cell hyperplasia (J Med Case Reports 2008;2:138)

Treatment

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● Simple excision with microscopic examination of entire specimen (Arch Pathol Lab Med 1991;115:137); must rule out mucinous DCIS or invasive mucinous carcinoma (Histopathology 2004;45:148)

Clinical images

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Gross description (Macroscopy)

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Gross images

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Mucin filled cysts contained DCIS

Micro description (Histopathology)

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● Mucin containing cysts that often rupture, with extravasation of mucin into surrounding stroma

● Epithelium lining the cysts may be benign/flat, hyperplasia, ADH, DCIS or mucinous carcinoma

● Myoepithelial cells adhere to strips of cells floating in lakes of mucin

● Calcifications are often present

Micro images

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Cysts contain mucin and are Mucin extravasation (arrows)

lined by cuboidal/columnar epithelium

Microcalcifications (arrows) Extravasated mucin with dense calcifications

associated with cyst and mild ductal hyperplasia

Mucocele-like tumor With focal columnar

cell hyperplasia

With florid epithelial hyperplasia

With ADH

With DCIS With mucinous carcinoma

Virtual Slides

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Videos

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Cytology description

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● Poorly cellular with cohesive clusters of bland cells in two dimensional sheets with abundant mucoid background, no/rare intact single tumor cells, no atypia if mucocele only (Am J Surg Pathol 1999;23:552)

● Excisional biopsy is necessary to confirm diagnosis (Breast Cancer 2009;16:77)

● Mucinous carcinomas are usually more cellular with more single tumor cells, 3D clusters, mild/moderate nuclear atypia, and a solid mass by imaging (Cytopathology 2004;15:104)

Cytology images

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Positive stains

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Negative stains

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Electron microscopy descriptions

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Electron microscopy images

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Molecular / cytogenetics description

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Molecular / cytogenetics images

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Differential Diagnosis

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● Mucinous (colloid) carcinoma: low grade tumor cells without adherent myoepithelium floating in a sea of lightly staining amorphous mucin

Additional references

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● Stanford University

End of Breast-nonmalignant > Benign tumors / changes > Mucocele like lesion

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