Melanins are naturally occurring pigments in both normal and pathologic tissues. Two common bleaching processes are potassium permanganate followed by oxalic acid treatment and dilute hydrogen peroxide (H2O2) process. The potassium permanganate/oxalic acid method is faster and more easily incorporated in conventional daily immunostaining protocols, whereas the dilute H2O2 method requires 24 hours. This study aimed to reduce melanin bleaching time by using a 10% H2O2 dilution. First, reaction time was reduced to 30 minutes by raising the temperature to 65°C. Second, containers with high thermal conductivity were used to improve bleaching effectiveness. Experimental comparisons of melanin treatments with H2O2 contained in an iron jar, a glass coplin jar, and a plastic steel jar obtained bleaching time of 20, 30, and 40 minutes, respectively. These modifications of the conventional bleaching method significantly improve the speed and efficiency of the procedure and are recommended when performing immunohistochemical studies.

The method is particularly effective for removing melanin pigment to facilitate histopathological examination of cytomorphology and for obtaining an unmasked tissue section for immunohistochemical analysis.

Malignant papillary lesions are, in contrast to their benign counterpart, rare malignant tumors in the breast. To differentiate between benign or atypical and malignant papillary lesions can be difficult, especially in core biopsy specimens. In the present study, excisional or more extensive surgical specimens of 33 papillary carcinomas, 2 micropapillary carcinomas, and 17 atypical papillomas of the breast were reviewed and classified according to the latest WHO classification. Thirty-three intraductal papillomas and 49 invasive carcinomas, no special type (NST), were included in the study for comparison. CD133 expression in papillary carcinomas was significantly lower than that in benign and atypical papillomas (p < 0.001). CD133 expression in invasive carcinoma NST was also significantly higher than that in papillary carcinomas. Our data suggests that absence of expression of CD133 can be a useful marker in the differential diagnosis between malignant papillary lesions and their benign or atypical mimics. The characteristic loss of CD133 expression in papillary carcinomas of the breast also indicates that these lesions are distinct from other types of breast cancer.