p40 as a Basal Cell Marker in the Diagnosis of Prostate Glandular Proliferations: A Comparative Immunohistochemical Study with 34betaE12

Diagnostic Value of Cytokeratin 34 beta E12 (Ck34βE12) and α-Methylacyl-CoA racemase (AMACR) Immunohistochemical Expression in Prostatic Lesions

Background & Objective

Some prostatic lesions contain small suspicious foci for prostatic carcinoma in which the morphological features are equivocal. Two immunohistochemical markers namely, cytokeratin 34 beta E12 (Ck34βE12) and α-Methylacyl-CoA racemase (AMACR), were evaluated in these lesions for a definitive diagnosis and avoiding misdiagnosis or overdiagnosis of prostatic carcinoma.

Methods

A total of 90 paraffin embedded blocks of prostatic tissue were selected and categorized into three groups as follows: 50 cases of benign prostatic hyperplasia (BPH), 20 cases of prostatic carcinoma, and 20 cases of benign prostatic lesions with suspicious foci labeled as ASAP (atypical small acinar proliferation) that occupy not more than 5% of the lesion. These cases were revised for histopathological diagnosis and stained with two immunohistochemical markers: Ck34βE12 and AMACR.

Results

While 92.9% of BPH were positive for Ck34βE12, 96% of prostatic carcinoma were negative for this marker (P=0.0001). Regarding AMACR, 92.9% of BPH cases were negative, but 92% of prostatic carcinoma cases were positive for this marker (P=0.0001). Out of 20 cases of BPH, 15 cases containing suspicious foci showed Ck34βE12+/AMACR- (diagnosis: benign), but 5 cases were Ck34βE12-/AMACR+, for which the diagnosis changed to prostatic carcinoma (P=0.04).

Conclusion

Immunohistochemical staining with Ck34βE12 and AMACR improved the diagnostic performance and increased confidence level for establishing definite diagnosis in cases with suspicious foci, in which the morphological features were equivocal. This could help to avoid misdiagnosis or overdiagnosis of prostatic carcinoma that would eventually improve the management of the patient and subsequently the prognosis.

P40 Immunostain Does Not Outperform p63 as a Myoepithelial Cell Marker in the Daily Practice of Breast Pathology

P40 antibody has been shown to be a more specific squamous and basal cell marker compared with p63. As detection of myoepithelial cells (MECs) plays a critical role in breast pathology, and the fact that p40 targets an isoform of p63, this study was designed to compare these antibodies in a variety of lesions, especially those with an sclerotic stroma and carcinoma in situ. All studied lesions were selected from the daily cases of the 3 authors and stained with p63, p40, and calponin immunohistochemical stains. Thirty-four cases (and 19 internal controls) were included. Seventy percent constituted sclerotic lesions (12 cases) and ductal carcinoma in situ (12 cases). P40 and p63 stained all lesions and showed a similar patchy staining pattern in 50% of ductal carcinoma in situ and sclerotic lesions. Compared with internal controls, p40 and p63 demonstrated decreased staining intensity in up to 70% and 8% of all cases, respectively, with no cross-reactivity with mesenchymal cells and minor cross-reactivity with epithelial cells. In our study, p40 did not outperform p63 as a MEC marker. p40 showed a decreased intensity in a higher number of cases (P<0.0001). In our opinion, p63 continues to be the best nuclear marker for the detection of MECs in the daily practice of breast pathology.