Medullary breast carcinoma

Medullary breast carcinoma is an uncommon form of invasive breast carcinoma.

It is also known as medullary carcinoma of the breast.

General

• Uncommon breast cancer subtype.
• Some pathologists very rarely make the diagnosis.^{[citation needed]}

Epidemiology:

• Thought to have a better prognosis that no special type (NST).
• May be associated with a BRCA1 mutation.

Gross

• Well-circumscribed border.

Aside - malignant well-circumscribed breast masses - radiologic DDx:

• Medullary breast carcinoma.
• Mucinous breast carcinoma.
• Malignant phyllodes tumour.
• Invasive papillary carcinoma of the breast.

Microscopic

Features:

1. Lesion has well-circumscribed border.
2. Syncytial growth pattern = clumps of cells with poorly defined cell borders.
3. Lymphocytic infiltrate.
4. High nuclear grade (as per Nottingham grading system).
5. No tubule formation.

IHC

Features - typical:

• ER -ve.
• PR -ve.
• HER2 -ve.

See also

• Invasive breast carcinoma.
• Medullary carcinoma.