Bone Marrow Smear - Iron Stain

Perls' Prussian blue stain (acid ferrocyanide reaction) is the standard stain to detect ferric (Fe3+) iron in bone marrow. It highlights hemosiderin and intracellular iron as blue granules within marrow macrophages and erythroid precursors, allowing assessment of iron stores. The reaction is performed on marrow aspirate smears or trephine sections and helps diagnose iron deficiency or overload.

Routine bone marrow smears are stained with Romanowsky-type stains—most commonly Wright–Giemsa (or May–Grünwald–Giemsa/Leishman)—to assess cellular morphology and perform differential counts. Special cytochemical stains (for example myeloperoxidase, NSE, or TRAP) may be added for lineage assignment or to identify specific disorders. Fixation is usually by air-drying with methanol prior to staining for optimal detail.

Bone‑marrow iron is assessed by obtaining a bone marrow aspirate and core biopsy, then staining marrow smears/sections with Prussian blue (Perls’) to detect and grade stainable iron in macrophages and erythroblasts. Pathologists report absent/low/normal/increased iron and note ring sideroblasts. This marrow stain is the gold standard to distinguish iron deficiency from anemia of chronic disease or sideroblastic anemia.

Absence of stainable iron in bone marrow indicates depleted body iron stores and is the gold-standard finding for iron deficiency. It typically accompanies iron‑deficiency anemia and shows reduced or absent hemosiderin in marrow macrophages. Causes include chronic blood loss, poor intake or absorption, and increased demand. This finding predicts impaired hemoglobin production and usually prompts evaluation and iron replacement.

The iron stain is called Prussian blue (Perls’ stain). It detects ferric iron (Fe3+) in tissues by producing an insoluble blue pigment when potassium ferrocyanide reacts with acid-extracted iron. Pathologists use it to identify hemosiderin and iron deposits in cells and tissues, helping diagnose hemorrhage, hemolysis, and iron-overload conditions.

For bone marrow aspirate smears, Romanowsky-type stains (Wright–Giemsa or May–Grünwald–Giemsa) are the standard for assessing cellular morphology. For core (trephine) biopsies, haematoxylin and eosin (H&E) is used. Special stains—Prussian blue for iron, myeloperoxidase and nonspecific esterase for lineage—are applied as adjuncts based on diagnostic needs.