INTRODUCTION- Melanoma is one of the most malignant tumors of the eye and conjunctiva. Excessive amount of melanin pigments in melanomas often hamper immunohistochemical assessment. The standard use of KMnO4 and K2Cr2O7 as bleaching agents has often been shown to alter the specificity and sensitivity of antigenic epitopes of the tissues thereby hindering IHC based investigation. Over expression of telomerase reverse transcriptase (TERT) has often been reported in various carcinomas leading to an increased in the activity of telomerase enzyme, which is crucial for survival of cancer cells .TERT promoter mutation are frequent in conjunctival melanoma, however its expression has not been reported in conjunctival melanoma due to presence of heavy melanin pigmentation which often interferes with 3,3’-diaminobenzidine (DAB) based immunohistochemistry. In this study we evaluated the use of Tricholoroisocyanuric acid (TCCA) solution as a cost effective and reproducible technique and also derived the chemistry behind bleaching of melanin pigment from melanoma tissue for immunohistochemical evaluation of conjunctival melanoma.

METHOD- 10 ocular melanoma samples were analyzed for TERT, KI-67 and HMB-45 immuno expression using monoclonal antibodies followed by DAB and TCCA treatment.

RESULT- Effective bleaching was achieved using freshly prepared 5% Tricholoroisocyanuric acid solution. HMB-45 was localized in cytoplasm and KI-67 positivity was observed in the nucleus. TERT expression was seen 70% cases of ocular melanoma. TERT nuclear positivity was also detected in patients with primary acquired melanosis.

CONCLUSION-The bleaching effect of TCCA solution on melanin pigments did not interfere with immunostaining using TERT antibody. The finding of this study advocates the use of TCCA solution for effective and rapid removal of melanin pigments from paraffin embedded sections to expose the epitopes for immunohistochemical analyses.