[759] Mass-Forming Intraductal Carcinoma of the Prostate

SW Fine, A Gopalan, SK Tickoo, VE Reuter. Memorial Sloan-Kettering Cancer Center, New York, NY

Background: The defining features of and clinicopathologic outcomes associated with intraductal growth of prostatic carcinoma (IDC-P) are controversial, with most considering it a late event in prostate cancer (CA) evolution. Mass-forming IDC-P, accounting for the bulk of tumor volume, has not been well studied.
Design: We identified 3 radical prostatectomy (RP) and corresponding needle biopsy (NB) specimens in which IDC-P represented > 70% of the tumor mass and evaluated architectural, cytologic, and topographic features of these lesions.
Results: RP: IDC-P comprised 70 to 90% of total tumor volume, with retained basal cell layers confirmed by immunohistochemistry (IHC) in all cases (RP and NB). Intraductal tumor masses were predominantly located in the peripheral zone, with one (case 3) extending to transition zone, periurethral ducts and urethral surface. A spectrum of architectural patterns was observed, including micropapillae and loose cribriforming (case 1), dense arborizing micropapillae (case 2), and dense cribriforming/solid growth (case 3), the latter accompanied by comedonecrosis. Cases 1 and 3 showed marked nucleomegaly in >70% of the IDC-P, while case 3 also had significant pleomorphism/frequent mitoses. The same cases showed 10% flat growth of IDC-P within acini. Case 2 showed marked atypia in 15% of the IDC-P and abundant macronucleoli in the remainder of the lesion. Gleason score of the invasive component was 3+4=7 for cases 1-2 (>80% pattern 3) and 4+3=7 for case 3 ( equal patterns 3 and 4). Extraprostatic extension was seen in cases 2-3. NB: Between 6 and 11 NB cores revealed IDC-P. In cases 1 and 3, IDC-P was recognized at diagnosis, while in case 2, IDC-P was identified retrospectively. In cases 1 and 3, IDC-P involved 10-95% of cores with minimal to no invasive CA. Micropapillary and loose cribriform (case 1) or dense cribriforming/flat growth (case 3) was observed, along with an equivalent level of nucleomegaly to that seen at RP. On careful review, positive NB from case 2 showed 5-20% IDC-P and up to 75% invasive CA, with arborizing micropapillary IDC-P architecture reminiscent of that seen at RP and moderate to focally marked cytologic atypia.
Conclusions: Intraductal spread of prostate CA may form expansile lesions. The limited and predominantly low grade invasive CA seen with mass-forming IDC-P suggests that intraductal growth is a primary pathway of prostate cancer spread. IDC-P is identified on needle biopsy by recognition of complex architecture +/- marked cytologic atypia, the latter of which may manifest as flat intra-acinar growth.
Category: Genitourinary (including renal tumors)

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 85, Tuesday Morning