ICD-10:

• N60.8 - other benign mammary dysplasias
• N60.9 - unspecified benign mammary dysplasia

ICD11:

• GB20.Y - other specified benign breast disease
• GB20.Z - benign breast disease, unspecified

• Based on histologic examination of removed tissue

Contributed by Iskender Sinan Genco, M.D. and Sabina Hajiyeva, M.D.

Contributed by Mark R. Wick, M.D.

• Myoepithelial cells: KIT / CD117, ER and CK7 (Mod Pathol 2006;19:1351)

• Adenoid cystic carcinoma:
  • Invasive pattern
  • Intraluminal material is denser
  • Myoepithelial cells are negative for CD10
  • Luminal cells are positive for KIT / CD117, negative for ER and PR
• Ductal carcinoma in situ, cribriform type:
  • Cribriform spaces are rounder and more regular (cookie cutter appearance)
  • No pink material present in cribriform spaces
  • Cribriform spaces surrounded by luminal cells, not myoepithelial cells
  • Negative for CK5/6
• Lobular carcinoma in situ, signet ring cell type:
  • Intracytoplasmic vacuoles
  • Negative for E-cadherin

Atypical ductal hyperplasia:

• Some, but not all, features of low grade ductal carcinoma in situ (see above)
• Negative for CK5/6

A premenopausal woman had a stereotactic breast core biopsy for calcifications. Microscopic examination revealed fibrocystic changes with microcalcifications as well as the microscopic finding shown above (H&E). Regarding this entity, which of the following statements is true?

1. Comprised of a clonal (neoplastic) proliferation
2. Epithelial cells interspersed between spaces are negative for ER
3. Flattened (myoepithelial) cells around spaces are positive for CD10
4. Luminal epithelial cells are positive for KIT / CD117
5. Surgical excision should be performed

C. The flattened (myoepithelial) cells around spaces are positive for CD10. The picture shows slightly expanded ducts with spaces filled with eosinophilic material. The spaces are surrounded by small oval / spindle myoepithelial cells with interspersed cuboidal luminal cells, features consistent with collagenous spherulosis. Collagenous spherulosis is a benign finding and does not require treatment. Adenoid cystic carcinoma is the main differential diagnosis which shows MYB-NFIB fusion gene, is negative for ER and PR, positive for KIT / CD117 and should be surgically excised.

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Reference: Collagenous spherulosis

A 34 year old woman was diagnosed with invasive ductal carcinoma on core biopsy and subsequently underwent surgical excision. One of the surgical specimen sections showed the microscopic lesion with cribriform architecture (middle) adjacent to invasive carcinoma. Based on the provided H&N, SMMH, and PAS stains, what is the correct diagnosis?

1. Atypical ductal hyperplasia
2. Collagenous spherulosis
3. Ductal carcinoma in situ
4. Lobular carcinoma in situ involving ductal carcinoma in situ
5. Usual ductal hyperplasia

B. Collagenous spherulosis

The H&E slide shows invasive carcinoma (upper), benign breast tissue (right lower), and a duct with cribriform architecture (middle). SMMH highlights the myoepithelial cells around the cribriform spaces and the periphery of the involved duct, whereas invasive carcinoma is negative for SMMH. This lesion with cribriform architecture represents collagenous spherulosis. PAS stain highlights the basement membrane material within the cribriform spaces produced by the surrounding myoepithelial cells. The other options may also show cribriform architecture but do not have myoepithelial cells surrounding the cribriform spaces. PAS stain helps confirm the diagnosis of collagenous spherulosis, but does not entirely rule out the other options.

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Reference: Collagenous spherulosis