Mycoses - Histology

What are Mycoses?

Mycoses are infections caused by fungi, which can affect various tissues and organs in the body. These infections can be superficial, affecting the skin and mucous membranes, or systemic, impacting internal organs. The study of mycoses in histology involves examining tissue samples under a microscope to identify fungal structures and understand the pathological changes they cause.

Types of Mycoses

Mycoses can be categorized into three main types: superficial, subcutaneous, and systemic.

Superficial mycoses: These affect the outermost layers of skin and hair. Common examples include tinea versicolor and tinea nigra.
Subcutaneous mycoses: These infections penetrate deeper into the skin, affecting the dermis and subcutaneous tissue. Examples include sporotrichosis and chromoblastomycosis.
Systemic mycoses: These are serious infections that can spread to internal organs. Examples include histoplasmosis, coccidioidomycosis, and cryptococcosis.

Histological Examination

The histological examination of mycoses involves the use of special stains and microscopic techniques to identify fungal elements within tissue samples. Commonly used stains include:

Periodic acid-Schiff (PAS) stain: This stain highlights fungal cell walls, making them appear magenta against a pink background.
Gomori methenamine silver (GMS) stain: This stain turns fungal elements black against a green background, enhancing visibility.
Hematoxylin and eosin (H&E) stain: While not specific for fungi, H&E can reveal tissue reactions and the presence of fungal structures.

Pathological Changes

Fungal infections can cause a variety of pathological changes in tissues:

Granuloma formation: Some fungi, like Histoplasma and Coccidioides, can induce granuloma formation, a type of chronic inflammatory response characterized by the presence of macrophages, giant cells, and lymphocytes.
Necrosis: Fungal infections can lead to tissue necrosis, which is the death of cells or tissues due to the destructive effects of fungal enzymes and toxins.
Vascular invasion: Some systemic fungi, such as Aspergillus, can invade blood vessels, leading to thrombosis and tissue infarction.

Clinical Relevance

The histological diagnosis of mycoses is crucial for guiding the appropriate treatment. Identifying the specific fungal pathogen helps in selecting the most effective antifungal therapy. Additionally, understanding the extent of tissue involvement and the host’s immune response can provide insight into the prognosis and potential complications of the infection.

Conclusion

Mycoses represent a diverse group of fungal infections with varying degrees of severity. Histological examination plays a key role in the diagnosis and management of these infections. By using specialized stains and techniques, pathologists can identify fungal elements and assess the pathological changes they induce, ultimately aiding in the delivery of targeted and effective treatment.