Pathology Associates Of Lexington, P.A.

Breast Epithelial Proliferations DIN

Championed by Dr. Tavassoli at Yale, "DIN" refers to
duct-epithelial proliferations (ductal intraepithelial neoplasia).

DIN Classification	non-DIN Designation	Pleomorphic Nuclear Atypia	Necrosis	Re-excision if Positive Margin
low risk DIN1	IDH, UDH (CCC)	- or +	no	n/a
DIN 1a <2mm	(CCH) ADH or tiny DCIS	- or +	no	no
DIN 1b	ADH, flat type (FEA)	-	-	?/no
DIN 1c >2mm	d-AIH or >2mm d-CIS grade I (cribriform or micropapillary)	-	-	yes
DIN2	d-CIS grade II (crib/micropap with necrosis or atypia); or special types, specify	- or +	+ (-)	yes
DIN3	d-CIS grade III (anaplastic d-CIS, +/- necrosis)	+++	+++/-	yes

DIN Low risk...usual intraductal hyperplasia (IDH)...with uneven nuclear spacing & lacking monotony.

Histological features, a key pearl: the stain for E-cadherin distinguishes l-CIS (E-cadherin negative) from d-CIS (E-cad positive). l-CIS & d-CIS can otherwise lokk alike.

DIN 1a...<2mm lesion (AIDH, ADH, DAH, d-AH, [& CCH]):

architectural...not enough for CIS vs LG-DCIS of tiny size.
- irregular fenestrations
- peripheral fenestrations
- stretched or twisted epithelial bridges
- uneven nuclear distribution and overlapping
cellular...not monotonous enough for CIS vs tiny LG-DCIS.
- multiple cell types (2 or more of epi, ME, or apocrine metas)
- cell appearances variation
- indistinct cell margins and non-round contours
- nuclear appearances variation

DIN 1b (flat type/FEA):

architectural...not enough for CIS.
- ductular profile is predominately "flat" (not papillary, solid, or bridged) but often "distended".
- single-cell lining layer, often focally multi-celled (3-5) thickness; cells often with apical "snouts".
- may contain secretory material or micro-Ca++.
cellular...not enough for CIS.
- mildly atypical incompletely monotonous cell lining (some Europeans call it "clinging ca., monomorphous type").

DIN 1c...a >2mm lesion (low grade, grade 1, DCIS...d-CIS):

architectural
- arcades, cribriform and/or micropapillary pattern involving anywhere from part of a single duct to multiple ducts or ductules
cellular
- monotonous population of uniform rounded cells
- subtle increase in n/c ratio
- equidistant or highly organized nuclear distribution
- round nuclei
- nuclear hyperchromia, +/-

DIN 2 (intermediate grade or grade 2 DCIS).

DIN 3 (high grade or grade 3 DCIS).

References:

Tavassoli seminar at MCG 21 April 2001, handout.
Tavassoli , Modern Pathology 11:140-45, 1998.
Tavassoli , Breast Journal 3:48-58, 1997.
Tavassoli, F. A., seminar at Pittsburgh, 4 May 2006, handout.

(posted 2001; updated 23 May 2006)