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Left breast core biopsy. Focal asymmetry of left breast on screening mammography.
Invasive lobular carcinoma (ILC) is the most common special type of breast carcinoma (2nd most common classification overall). It is typically composed of discohesive cells arranged singly or in files, usually with loss of E-cadherin.
This slide shows a widely infiltrative lesion with single cell filing, consistent with a diagnosis of invasive lobular carcinoma.
On biopsies, even with clear features, it may be prudent to shy away from the diagnosis of ILC, considering the possible sampling issue. Instead, "invasive mammary carcinoma, with lobular features" is commonly used. Pathologists should also examine for in situ lobular carcinoma.
Occasional signet ring cells can be appreciated. In rare cases, a diagnosis of diffuse gastric carcinoma may be entertained, if clinical history supports it.
See LMP57200-Invasive lobular carcinoma, for another example of this entity (link in related content).