Chromium pigment in fixed tissue is:

• A. Not preventable and cannot be removed.
• B. Preventable and can be removed in 1% HCl in 70% alcohol for 30 minutes.
• C. Removable only by sodium thiosulfate.
• D. Removed by plain water.

Answer: (B)

Chromium pigment forms when tissue is fixed with chromium-containing fixatives; it appears as a dark, insoluble deposit that can obscure microscopic detail. It is preventable by using a non-chromium fixative or avoiding chromium in the fixation process. If the pigment is already present, it can be removed by treating the tissue with dilute hydrochloric acid in 70% alcohol, typically for about 30 minutes. Plain water won’t dissolve the pigment, and sodium thiosulfate is not the standard remover for this pigment. This acid-alcohol step is the established method to remove chromium pigment, making the tissue suitable for accurate staining and interpretation.