An iron stain is a laboratory test that shows where iron is stored in a tissue sample. It colors iron bright blue so a pathologist can see it under the microscope. The most common iron stain is called Prussian blue, also known as the Perls stain.
An iron stain is a special stain, not a diagnosis. It is most often used on bone marrow and liver samples to measure how much iron the body has stored. This article explains how an iron stain works, why it is used, and what the results in your pathology report mean.
Iron is needed to make hemoglobin, the protein in red blood cells that carries oxygen. The body stores iron for when it is needed. Most stored iron is found in the bone marrow, liver, and spleen.
In tissue, stored iron is packed into a golden-brown pigment called hemosiderin. Hemosiderin is also left behind when red blood cells break down after bleeding. The iron stain shows both.
The iron stain is performed on a thin slice of tissue on a glass slide. A chemical solution is added that reacts with stored iron and forms a bright blue product. Any iron in the tissue turns blue, while the rest of the tissue stays pale pink or red. The stain does not react with other brown pigments, such as melanin.
An iron stain is used in several situations:
For bone marrow and liver samples, iron stain results are usually reported as a grade or a description. Your report may describe iron stores as:
Some reports use a number scale instead. The report may also say whether ring sideroblasts were seen and, if so, what percentage of developing red blood cells they make up.
For skin and other tissue samples, the report usually says only whether the pigment was positive or negative for iron.
The meaning of an iron stain depends on why it was done. Your doctor will interpret the results together with blood tests, such as an iron panel, and the rest of your pathology report.