Medullary breast carcinoma

Medullary breast carcinoma
Diagnosis in short
LM	all required: (1) lesion has well-circumscribed border, (2) syncytial growth pattern, (3) lymphocytic infiltrate, (4) high nuclear grade (as per Nottingham grading system), (5) no tubule formation
LM DDx	Invasive ductal carcinoma with medullary features
IHC	ER -ve, PR -ve, HER2 -ve
Site	breast - see invasive breast cancer
Prevalence	uncommon
Prognosis	better than NST

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.

DDx:

• Invasive ductal carcinoma with medullary features.

IHC

Features - typical:

• ER -ve.
• PR -ve.
• HER2 -ve.

See also

• Invasive breast carcinoma.
• Medullary carcinoma.