Significance of Paneth cell–like differentiation in prostatic adenocarcinoma: a retrospective cohort study of 80 cases

The grading and prognosis of prostatic adenocarcinoma with Paneth cell–like differentiation (PanEC) is controversial with limited available data. We identified 80 cases, not previously published, of PanEC first identified on biopsy (n = 69), transurethral resection of the prostate (n = 1), and radical prostatectomy (RP) (n = 10). Of 69 biopsies, 22 did not have a grade assigned. In the remaining 47 biopsies, the Grade Groups (GGs) of the associated usual prostatic adenocarcinoma were GG1–2 (n = 34) and GG3–5 (n = 13). Of 10 RPs, the GGs were as follows: GG1–2 (n = 8), GG4 (n = 1), and no grade due to treatment effect (n = 1); pathological stages were pT2 (n = 8) and pT3a (n = 2), all with negative lymph nodes. We analyzed 19 cases with available follow-up only associated with GG1–2 conventional cancer; 9 underwent RP, and GGs at RP were as follows: GG1–2 (n = 7), no grade due to treatment effect (n = 1), and missing data (n = 1); pathologic stages were pT2 (n = 6) and pT3a (n = 3); there were no positive regional lymph nodes; 3 were managed with active surveillance, without follow-up progression; 5 patients underwent radiation therapy with or without hormone therapy; none showed follow-up progression; 2 (10.5%) patients were recommended to undergo radiotherapy, with no further follow-up. Of the cases with available follow-up, 9 were not associated with conventional adenocarcinoma; the majority of these cases were treated with radiation therapy or active surveillance without evidence of progression. In summary, although a minority of PanECs are associated with conventional higher grade adenocarcinoma and have progression after treatment, the majority have favorable findings, justifying the consideration of them as more indolent tumors despite cases in which PanEC resembles Gleason pattern 5 adenocarcinoma.