What is haematoxylin?

HAEMATOXYLIN:

• Derived from the wood Haematoxylum campechianum.
• It means bloodwood  - refers to the dark red colour (Haemato -  blood, xylon- wood)

• Campechianum  refers to the coastal city of Campeche on the Yucatan Peninsula, the locality of the heart wood.

Pic: Google

If Haematoxylum is red, how is haematoxylin blue?

• Haematoxylin has little or no staining capacity.
• Haematoxylin is oxidised to haematein which gives the blue colour.
• Oxidation - two methods - 1. Natural 2. Chemical

Haematoxylin versus Haematein:

If hematein is the dye and haematoxylin needs to be oxidised before it can stain, why not use hematein in the first place?

• If we start with hematein, oxidation will start to diminish the staining capacity right from the start, shortening the working life of the solution ☺☺

Mucormycosis - How to identify?

Mucormycosis 

Predisposing factors:

• Transplant recipients
• Uncontrolled diabetes mellitus
• Patients with hematological malignancies
• Immunosuppressed patients
• People living with HIV (PLHIV)

HOW TO IDENTIFY MUCORMYCOSIS:

Broad, aseptate fungal hyphae, branching at 90 degree.
Angioinvasion is frequently seen, leading to thrombosis of vessels and tissue infarction & necrosis.
Mucor is always seen as a basophilic "glassy" structure on H&E staining.

Pic shows fungal hyphae with right angled branching.

PAS and Silver Methanamine stain highlight the fungal hyphae.

Pic: PAS stain

Silver methanamine: Arrow points to the blood vessel, fungal hyphae are seen infiltrating the wall. 

DIFFERENTIAL DIAGNOSIS:
ASPERGILLUS:
Slender, septate hyphae with acute angle branching.


Note: Candida species is often seen with Mucor and Aspergillus.