Melanin Solubility in Tissue Sections

Abstract

QUANTITATIVE estimations of staining reactions and histochemical observations on melanomas are not readily made because cellular detail is often obscured by melanin granules. One of the most promising solvents for melanin is ethylene chlorohydrin¹. This solvent, and others mentioned by Mason² (alcohol, pyridine and water), are said to be satisfactory only after melanin has been separated from its protein component. Neither ethylene chlorohydrin nor any of the other solvents removed melanin from tissue sections in the following experiments. Tissue blocks from a malignant melanoma and from negro skin were fixed in a variety of fixatives and were dehydrated and embedded in paraifin. Sections were treated with ethylene chlorohydrin (Eastman Kodak) and with pyridine, at 22° and at 60° C., for periods from fifteen minutes to twenty-four hours. No diminution in the amount of melanin was observed in any of the sections. Frozen sections of unfixed negro skin were prepared by the Adamstone–Taylor technique³ and immersed without fixation or other pre-treatment in pyridine and ethylene chlorohydrin. The structure and staining reactions of the sections were markedly altered, as they were in those sections heated to 60° (above), but there was no decrease in the amount of melanin.