Iron Stain: Definition

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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.

Where is iron stored in the body?

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.

How does an iron stain work?

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.

Why do pathologists use an iron stain?

An iron stain is used in several situations:

To measure iron stores in the bone marrow. An iron stain is routine in many bone marrow biopsies. Low stores support a diagnosis of iron deficiency anemia. High stores can point to iron overload or other blood conditions.
To look for ring sideroblasts. Ring sideroblasts are developing red blood cells with a ring of iron granules around the nucleus. They can indicate myelodysplastic syndrome and other conditions.
To measure iron in the liver. Too much iron can build up in the liver and damage it. An iron stain shows how much iron is present and which cells contain it.
To identify a brown pigment. Hemosiderin and melanin can look similar on routine slides. The iron stain turns hemosiderin blue but does not stain melanin. This helps the pathologist distinguish old bleeding from pigment made by skin cells.

How are iron stain results reported?

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:

Absent or decreased. Little or no stored iron is seen. This suggests the body does not have enough iron.
Normal or adequate. The amount of stored iron is within the expected range.
Increased. More stored iron than expected is seen. This can happen with repeated blood transfusions, some inherited conditions, and some blood disorders.

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.

What do the results mean for me?

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.

Questions to ask your doctor

Why was an iron stain done on my sample?
Were my iron stores low, normal, or high?
Were any ring sideroblasts seen?
Do the results match my blood iron tests?
Does the result change my diagnosis or treatment?
Do I need any further tests?