Other invasive carcinoma subtypes, WHO classified


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Last staff update: 23 September 2022

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PubMed Search: Microinvasive carcinoma

Monika Roychowdhury, M.D.
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Cite this page: Roychowdhury M. Microinvasive. website. Accessed September 30th, 2023.
Definition / general
  • Dominant lesion is not invasive, but there are 1+ separate small, microscopic foci of infiltration, each 1 mm or less in size
  • “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
  • Mean age 61 years
Clinical features
  • 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
Microscopic (histologic) description
  • 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
Microscopic (histologic) images

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

Figures 1, 2 and 3

Figure 1

Negative stains
Additional references
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Image 01 Image 02