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Breast malignant, males, children

Breast cancer

Microinvasive carcinoma


Reviewer: Monika Roychowdhury, M.D. (see Reviewers page)
Revised: 19 December 2012, last major update February 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

Definition of microinvasion
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● Dominant lesion is not invasive, but there are 1+ separate small, microscopic foci of infiltration, each 1 mm or less in size

Terminology
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● “Minimal breast carcinoma” includes microinvasive carcinoma and DCIS
● Can confirm using myoepithelial stains (myoepithelial layer is not intact) and keratin (to observe infiltrative growth)
● Diagnosis requires certainty of invasion; if doubt remains after recuts and immunostains, call DCIS or suspicious

Epidemiology
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● Mean age 61 years

Clinical description
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● Less than 1% of all breast cancers
● Usually detected by mammography due to abnormal calcifications in associated DCIS
● 72% associated with comedo DCIS, 89% with high nuclear grade and 89% with necrosis
● Sentinel lymph node dissection may be appropriate, although axillary nodal metastases occur in less than 10% (Breast J 2008;14:335, Breast 2008;17:395); controversial whether to perform complete axillary dissection if positive sentinel node (yes - Breast 2007;16:146, no - Am J Surg 2007;194:845)
● Commonly misdiagnosed, as true diagnosis is usually DCIS or T1a carcinoma (Cancer 2000;88:1403)
● In breast core needle biopsies, invasive carcinomas 1 mm or less are rare, are associated with DCIS and ADH, and often with large invasive foci at excision (Arch Pathol Lab Med 2004;128:996)
● Report number of foci of invasion, size of largest focus

Treatment and prognosis
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● Cure rate is close to 100% with surgical excision (Ann Oncol 2004;15:1633)
● Prognosis may depend on features of DCIS (Am J Surg Pathol 2000;24:422)
● Natural history closely resembles that of DCIS; thus, microinvasion alone should not be the sole criterion for more aggressive treatment (Int J Radiat Oncol Biol Phys 2012;82:7)

Micro description
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● Usually ductal, rarely tubular or lobular morphology
● Nodules of invading neoplastic cells in periductal or perilobular stroma, none exceeding 1.0 mm
● Usually arises in background of high grade DCIS; stromal microinvasion typically associated with fibroblast proliferation, collagenization and focal inflammation
False positives: lobular cancerization, radial scar, sclerosing adenosis (Arch Pathol Lab Med 2001;125:1259)
False negatives: masking of invasion by inflammatory cells or histiocytes; use cytokeratin to highlight tumor cells

Micro images
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With high grade DCIS


Examples from core biopsies

   
Tumor breaches basement membrane


Fig A: false negative due to inflammatory cells
Fig B: false negative due to mistaking tumor cells for histiocytes
Fig C: AE1-3 distinguishes tumor cells (+) from inflammatory cells (-)
Fig D: smooth muscle actin highlights myoepithelial cells in benign but not malignant lesions



Invasive carcinoma (arrow) < 1 mm, surrounded by DCIS


High grade DCIS with foci of microinvasion


Figure A


Figures 1, 2, and 3


Figure 1

Negative stains
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● Myoepithelial layer is not intact in invasive component (detected with smooth muscle myosin heavy chain, smooth muscle actin, calponin, p63)

Additional references
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Hum Pathol 1998;29:1412

End of Breast malignant, males, children > Breast cancer > Microinvasive carcinoma


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