Pathology

Billis, Athanase

doi:10.1590/S1677-55382003000300016

UROLOGICAL SURVEY

Pathology

Basal cell cocktail (34bE12 + p63) improves the detection of prostate basal cells

Zhou M, Shah R, Shen R, Rubin MA

University of Michigan School of Medicine, Ann Arbor, MI

Mod Pathol. 2003; 16: 177A

BACKGROUND: High molecular weight cytokeratin (34bE12) and p63 are frequently used as basal cell markers in aid of diagnosis of prostate cancer (PCa). Absence of a basal cell marker in an atypical lesion histologically suspicious for PCa supports a malignant diagnosis. Yet, absence of basal cells by immunohistochemistry (IHC) is not always conclusive. Improving the sensitivity of basal cell IHC is critical to help make diagnostic decisions in conjunction with standard histology. We test the hypothesis that inclusion of both 34bE12 and p63 in a cocktail reaction is advantageous over either marker used alone.

DESIGN: 1350 benign glands from 9 TURP specimens were use to study the immunostaining intensity and pattern for 34bE12, p63 and the basal cell cocktail. Basal cell marker expression was scored as strong, moderate, weak and negative. Basal cell staining was considered complete if 75% of the gland circumference was positive for the basal cell marker, and partial if 25% of the circumference was stained.

RESULTS: By IHC, benign glands lack basal cell lining in 2, 6 and 2% of glands with cocktail, 34bE12 and p63 staining, respectively. The staining variance for cocktail is significantly smaller than that for 34bE12 (0.0100 vs. 0.1559, p=0.0008). No significant difference was seen between cocktail and p63 (0.0100 vs. 0.0345, p=0.099). The cocktail stains the basal cell layers more intensely than either 34bE12 or p63 alone, with complete and partial strong basal cell staining in 93 and 1 % of benign glands, compared to 55 and 4% with 34bE12, and 81 and 1% with p63. Complete and partial weak staining is seen in 0 and 0% of benign glands with the cocktail, compared to 8 and 7% with 34bE12 and 4 and 1% with p63 (p=0.007 and 0.014 for cocktail vs. 34bE12 and cocktail vs. p63, respectively). 2.8% of clinically localized PCa had positive 34bE12 staining and 0.3 % had positive p63 staining.

CONCLUSIONS: IHC of the prostatic glands from transition zone is subject to staining variability. 34bE12 is most susceptible, and basal cell cocktail is least susceptible to such variability. Basal cell cocktail not only increases the sensitivity of the basal cell detection, but also reduces the staining variability and therefore renders the basal cell IHC more consistent.

Editorial Comment

Basal cells are of utmost importance for the diagnosis of adenocarcinoma of prostate. Their presence excludes this diagnosis. Their absence, however, does not mean necessarily that the acinus's is neoplastic. Most of the times their presence is recognized on hematoxylin and eosin stains. They are located close to the basement membrane, are round, oval or pyramidal and sometimes the nucleus is involved by a clear halo. They are precursors to the secretory cells and not myoepithelial cells.

In cases of "atypical small acinar proliferation" (ASAP) the presence of basal cells may help a final diagnosis of adenocarcinoma. ASAP is used in cases of "suspicious but not diagnostic of adenocarcinoma". I prefer this last expression because ASAP may give the impression of an entity or a particular lesion. It only expresses lack of some criteria for the definitive diagnosis of adenocarcinoma.

In this circumstance the immunostaining for basal cells is critical for the diagnosis. The pathologist uses high molecular cytoqueratins (34bE12) to disclose these cells. Not always this stain is uniform and uncertainty remains as to the correct diagnosis. The cocktail, that is, adding to 34bE12 the p63 seems to improve the efficacy of this immunostaining. We hope that other studies confirm the findings of this paper considering that using 2 antibodies makes the immunostaining more expensive.

Dr. Athanase Billis

Department of Pathology

State University of Campinas, Unicamp

Campinas, São Paulo, Brazil

The addition of a negative 34bE12 stain to a small focus of atypical glands on prostatic core biopsies does not predict a higher incidence of prostatic adenocarcinoma on follow up biopsies

Halushka MK, Kahane H, Epstein JI

The Johns Hopkins Hospital, Baltimore, MD; Dianon Corp., Stratford, CT

Mod Pathol. 2003; 16: 152A

BACKGROUND: Atypical glands on prostate needle biopsy with a negative 34bE12 immunostaining, indicating a lack of a basal cell layer, are typically diagnostic criteria of prostate cancer. However, there are certain cases in which a negative 34bE12 immunostaining in a small focus of atypical glands is still not convincing enough to make the diagnosis of cancer. This study is the first report to evaluate the incidence of prostate cancer on follow-up biopsy in individuals with this diagnosis.

DESIGN: 543 men who had prostate core biopsies diagnosed as a small focus of atypical appearing glands with a negative 34bE12 immunostaining between 1/1/97 and 12/31/00 were selected for study.

RESULTS: 61% of the 543 individuals had at least one follow up biopsy (n=332). Of these, 43% of repeat biopsies were diagnostic of prostate cancer (n=142). 46 men had at least 2 follow up biopsies, with 48% of these (n=22) being diagnosed as cancer. The percent of carcinomas having Gleason grades 3+2=5, 3+3=6, 3+4=7, 4+3=7 and 4+4=8 were 6%, 86%, 1%, 4% and 3% respectively. The median amount of time to the first follow up biopsy was 79 days, with 52% of follow up biopsies being performed within 90 days.

CONCLUSIONS: A negative 34bE12 immunohistochemical stain in a small focus of atypical glands is not associated with an increased prediction of prostate cancer on follow up biopsy (43%), compared with previously published data for "small focus of atypical glands" alone (approximately 45%). As 48% of men with an initial negative biopsy and multiple follow up biopsies were found to have cancer, more than one repeat biopsy or more extensive sampling on first repeat biopsy may be necessary to maximize the identification of cancer. This is the same as has been shown for men with atypical diagnoses in general, without a negative 34bE12 immunohistochemical stain. Only half of all individuals with a diagnosis of 34bE12 negative focus of atypical glands were rebiopsied within 3 months. Urologists need to be educated as to the significance of an atypical diagnosis and the need for rebiopsy.

Editorial Comment

The presence of basal cells excludes the diagnosis of adenocarcinoma but their absence does not mean necessarily that the acinus is neoplastic. This article emphasizes the need of morphologic criteria for the diagnosis of adenocarcinoma. The pathologist should not rely on his diagnosis exclusively on the result of immunostaining.

In cases of "atypical small acinar proliferation" (ASAP), immunostaining is indicated to help making the diagnosis of adenocarcinoma. This study, however, showed that a negative 34bE12 immunohistochemical stain in a small focus of ASAP is not associated with an increased prediction of prostate cancer on follow up biopsy (43%), compared with previously published data (approximately 45%).

In cases of ASAP the pathologist, besides immunostaining, performs new sections in other levels of the biopsy hoping the lesion appears more extensive. In cases the immunostaining does not show basal cells but the morphologic criteria are still not sufficient for the diagnosis of adenocarcinoma, the diagnosis is ASAP and not adenocarcinoma.