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Breast-malignant, males, children
Microinvasive carcinoma
Author: Nat Pernick, M.D, PathologyOutlines.com, Inc.
Reviewer: Daniel Visscher, M.D., University of Michigan Hospitals, February 2009 (see Reviewers page)
Revised: 13 September 2009
Last major update: September 2009
Copyright: (c) 2002-2009, 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
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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 (Archives 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 (AJSP 2000;24:422)
Microscopic 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 (Archives 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
Microinvasion (arrow) and High grade DCIS with Low grade cribriform DCIS
chronic inflammation focus of microinvasion < 1 mm with focal microinvasion just beyond
TDLU (arrows)
Examples from core biopsies
Figure A Fig A: DCIS with foci equivocal for microinvasion,
Fig B: DCIS with early microinvasion,
Fig C: DCIS with late microinvasion, Fig D: small invasive ductal
carcinoma (T1a), the breast lobule shows both DCIS (left) and
invasive carcinoma (right)
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
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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End of Breast – Malignant, Males, Children > Microinvasive carcinoma
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