Introduction

During histological fixation of the formaldehyde solution (primarily, the samples containing larger amounts of blood such as the liver and bone marrow samples), in cells and outside the cells small brown/dark brown diamond shaped crystals form. Formalin pigments are methemoglobins (hemateins) formed by hemoglobin oxidation in a non-buffered formaldehyde solution. Kardasewitch solution (consisting of ammonia and alcohol) is routinely used for removing formalin pigment. Pigments that are successfully removed using this method are formalin pigments and hemozoin, while pigments hemosiderin, melanin and lipofuscin are not removed using this method.