Medullary Carcinoma

 

Epidemiology:

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Common sites:

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Gross features:

    • well-circumscribed mass
    • soft, fleshy consistency

 

Histologic features:

    • solid, syncitium-like sheets occupying >75% of tumour
      • poorly differentiated by definition
    • large cells
    • vesicular, pleomorphic nuclei
      • prominent nucleoli
    • frequent mitoses
    • lymphoplasmacytic infiltrate surrounding and within the tumour
    • pushing border

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

 ER, PR (neg)

 

 

 

Molecular features:

    • aneuploid
    • no HER2/neu overexpression
    • hypermethylation of BRCA1 promoter (67%)
    • familial:
      • 13% of BRCA1 tumours

 

Other features:

    • slightly better prognosis than NST
    • lymph node mets are infrequent
    • may be mistaken clinically for a fibroadenoma
    • often rapid, almost explosive growth
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