Infiltrating Syringomatous Adenoma of the Nipple

Definition

Located in dermis and subcutis of nipple and areola
Infiltrating round to irregular tubules, often compressed and comma shaped
- Resembles syringoma
- Lumens may contain amorphous, eosinophilic material or keratin
- Infiltrates into smooth muscle bundles
- Perineural invasion may be present
Myoepithelial cells present around tubules
- Results in a prominent expanded, at least double cell layer
Squamous differentiation variable (5-80% of tubules)
- Superficial keratin filled cysts may be present
Abundant desmoplastic collagenous stroma
Bland cytology
- Mitotic figures rare
- No necrosis
It has been proposed that this is the same lesion as low grade adenosquamous carcinoma of the breast differing only in location
- Adenosquamous carcinoma rarely may metastasize but this has not been reported for syringomatous adenoma