Collagenous Spherulosis

Definition

Intralumenal process
- Partially fills terminal ducts or acini
Aggregate of acellular eosinophilic spherules imparts a cribriform appearance
- 20-100 microns diameter
- Few to 50 spherules per section of lesion
- Usually discrete but may coalesce
- Basophilic, mucinous variant has been reported
Spherules show fibrillar structure, usually concentric or with radial spikes
- Other patterns
  - Hollow with eosinophilic cuticle
  - Hyaline eosinophlic granules, 1-2 microns
- May have associated microcalcification
Cellular component is mixed epithelial and myoepithelial
- Myoepithelial cells surround spherules and whole lesion
- Small round cytologically bland cells
  - Identical in size and appearance to normal duct lining cells
- No mitotic figures
Nearly always an incidental microscopic finding
- Usually confined to one medium or high power field
  - Two cases reported 2-3 mm diameter
  - May be multifocal
- One case reported to be palpable
- May be biopsied because of associated microcalcifications