General
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Well circumscribed, composed of poorly differentiated cells in syncytia or large sheets, with prominent lymphoplasmacytic infiltrate, scant fibrous stroma, no glandular structures, minimal DCIS
Indistinct cell borders (syncytial growth) making up 75%+ of tumor with large pleomorphic tumor cells containing large nuclei, prominent nucleoli, numerous mitotic figures; peripheral cells are more eosinophilic
Prominent lymphoplasmacytic infiltrate at periphery composed of T cells and IgA plasma cells
Pushing borders / well circumscribed
Classify as medullary carcinoma if tumor has above three features
Classify as atypical medullary carcinoma (or infiltrating ductal carcinoma) if tumor has only 2 of 3 features listed above (atypical medullary carcinoma has similar prognosis as ductal carcinoma NOS)
Other features:
Sparse stroma
Variable spindle cell or squamous metaplasia, occasional bizarre tumor giant cells and extensive necrosis
No/minimal glandular differentiation, no intraductal growth or DCIS, no mucin, no calcification
Clusters of sheets of syncytial cells with prominent lymphoplasmacytic infiltrate
Various images
Lymphocytes in micropapillary and medullary carcinomas
ER negative
p63
p53
HER2 staining (usually is negative, in this case, is focally 3+ [see image on right])
High grade syncytial pattern
Tumor cells have syncytial pattern and high grade nuclei, necrosis
at upper left, lymphoplasmacytic infiltrate at lower right (AFIP)
A lobule with in situ carcinoma in some lobular units;
thick basement membranes, are nonspecific feature (AFIP)
Focal areas of squamous metaplasia with keratin pearls
Note solid growth pattern with distinct cell membranes
(not syncytia) in areas of squamous metaplasia (AFIP)
Atypical medullary carcinoma
Tumor invades fat and is not well circumscribed (AFIP)
Medullary features include poorly differentiated nuclei,
syncytial growth, lymphoplasmacytic infiltrate (AFIP)
Atypical medullary carcinoma because no lymphoplasmacytic infiltrate
End of Breast malignant, males, children > Carcinoma subtypes > Medullary carcinoma
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