Prostatic Intraductal Adenocarcinoma

Definition

Considered to represent high grade prostatic adenocarcinoma that has gained access to pre-existing large acini and ducts
- Edges of tumor are smooth rather than raggedly infiltrating
Nearly always associated with high grade acinar carcinoma
- Gleason pattern 5 present in about half
- Very rare cases with no associated usual invasive carcinoma raise the possibility that in some cases this is a precursor lesion
Basal cells must be present at the periphery
- May be patchy
Must fulfill one of the following three architectural/cytologic criteria
- Solid or dense cribriform
  - Lumens comprise <50% of the total ductal lumen
- Loose cribriform (>50% lumens) but with marked nuclear pleomorphism
  - Many nuclei at least 6 times larger than normal
  - Large cells may be peripherally located
- Loose cribriform but with more than focal comedonecrosis
Differential diagnosis
- High grade PIN must be excluded

Prostatic Intraductal Adenocarcinoma	High Grade PIN
Cribriform pattern common	Cribriform pattern rare
Mitotic figures common	Mitotic figures rare
Basal cells if present are usually patchy	Basal cells widespread but may be fewer than normal
Solid or dense cribriform patterns are definitional	Solid and dense cribriform patterns not allowed
Marked nuclear pleomorphism (6 x normal) or comedonecrosis are definitional	Marked nuclear pleomorphism and comedonecrosis not allowed

The distinction from invasive cribriform acinar adenocarcinoma should be made
- Although both are high grade carcinomas, intraductal carcinoma is more aggressive

Prostatic Intraductal Adenocarcinoma	Cribriform Acinar Adenocarcinoma
May have marked cytologic atypia (6x normal)	Nuclei atypical but not markedly enlarged
Basal cells present	Lacks basal cells
Smooth edges without infiltration	Frequently has ragged infiltration at edges

Both are high grade carcinomas
Ductal carcinoma may have an intraductal component
- Demonstrated by focal presence of basal cells

Prostatic Ductal Adenocarcinoma	Non-ductal Intraductal Adenocarcinoma
Columnar cells with elongated nuclei	Cuboidal cells with round nuclei
Cribriform lumens frequently slit-like	Cribriform lumens usually round
Frequently has true papillae with vascular cores	Tufts but no true papillae
Usually lacks basal cells	Basal cells always present
Nuclear size 2-3 x normal	Nuclear size may be 6 x normal

Intraductal adenocarcinoma with a solid pattern may be confused with urothelial carcinoma growth into prostatic ducts

Prostatic Intraductal Adenocarcinoma	Urothelial Carcinoma Involving Prostatic Ducts
PSA and PAP positive	PSA and PAP negative
HMWCK and p63 negative	HMWCK and p63 positive

For general diagnostic, grading and staging criteria, see also Prostatic Acinar Adenocarcinoma

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