Mercury Pigment in Histologic Sections

 

Recognition:

(1) history of fixation in a mercury-based fixative

(2) presence of one or more of the following:

(2a) monorefringent brown-black extracellular crystalline deposits

(2b) birefringent brown-black extracellular crystalline deposits

(2c) globule deposits with a birefringent Maltese cross (appear in stored slides)

 

The pigment can be removed by treating the deparaffinized section:

(1) soaking in an iodine solution (Lugol's, other), followed by

(2) bleaching with hypo (weak sodium thiosulfate) solution

 

The treatment to remove the mercury pigment may interfere with some special stains so should be done before the special stain is performed.