Surgical Pathology Criteria

Mammary Hamartoma

Differential Diagnosis

Nonspecific fibrocystic disease

Adenomyoepithelioma Myoid Hamartoma
Myoepithelial component positive for keratin, p63, smooth muscle actin Myoid component positive only for smooth muscle actin
Tubules without lobules Well formed ducts and lobules
No admixed fat Admixed fat

Cowden disease

Fibroadenoma Mammary Hamartoma
Lobules infrequent Lobules typically present (may be atrophic)
Frequent intracanalicular or tubular glandular proliferation Morphologically normal ducts and lobules
Intralesional fat rare Fat integral to lesion

Diabetic Mastopathy / Lymphocytic Mastitis Mammary Hamartoma
Epithelioid stromal cells No epithelioid stromal cells
Prominent B cell infiltrates No significant B cell infiltrates
Both have keloidal fibrosis

Intramammary lipoma vs Adenolipoma

Mammary Hamartoma Gynecomastia-like Lesion of the Female Breast
Circumscribed Not circumscribed
Contains lobules No lobules
No periductal stromal changes Periductal stromal fibrosis or edema
May contain stromal smooth muscle or cartilage No stromal smooth muscle or cartilage

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