Low Grade Adenosquamous Carcinoma of the Breast

Definition

Low grade breast carcinoma exhibiting both glandular and squamous differentiation characterized by infiltrating, frequently compressed lumens

Infiltrating round to irregular tubules, often compressed and comma shaped
- Resembles syringoma
- Lumens may contain amorphous, eosinophilic material or keratin
Myoepithelial cells prominently present around tubules
- Results in at least a double cell layer
Squamous differentiation variable (5-80% of tubules)
- Overt keratinization less common than intercellular bridges
Abundant collagenous stroma
- 2 of 32 cases reported with osteocartilaginous metaplasia of stroma
- Occasional lymphoid nodules present
Bland cytology
- Mitotic figures rare
- No necrosis
May be associated with other lesions
- 12/32 cases associated with intraductal papillary lesions
- 3/32 cases associated with adenomyoepithelioma
- 3/32 cases associated with collagenous spherulosis
May be considered a low grade variant of metaplastic carcinoma or an adenomyomatous lesion
- It does not fulfil the strict definition of adenomyoepithelioma
It has been proposed that this is the same lesion as infiltrating syringomatous adenoma of the nipple differing only in location
- Adenosquamous carcinoma rarely may metastasize but this has not been reported for syringomatous adenoma

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting / updates: 5/1/06, 12/25/12