Mycotic Lesions in Surgical Pathology.

The Fungal Diseases Are Grouped Arbitrarily Into Four Broad Categories Based On
The Predominant Location Of Infection Within The Body As Superficial, Cutaneous,
Subcutaneous And Systemic Infection. Superficial Mycoses Are Those In Which The Fungus
Is Usually Confined To The Keratinized Layer Of The Skin And Its Appendages. The
Cutaneous And Subcutaneous Mycoses Are A Polymorphic Group Of Diseases Caused By A
Variety Of Fungi. Systemic Mycoses Usually Have A Pulmonary Inception From Which
They Disseminate To Other Organs.
Most Fungal Infections Occur Because A Person Is Exposed To A Source Of Fungi
Such As Spores On Surfaces Or In The Air, Soil Or Bird Dropings. Usually There Is A Break Or
Deficiency In The Bodys Immune System Defences And The Person Provides The “Right
Environment” For The Fungi To Grow. Any One Can Have A Fungal Infection But Certain
Populations Are At Increased Risk Of Fungal Infections And Recurrence Of The Infection.
These Include HIV–AIDS Spectrum, Malignancy, Multidrug Resistant Tuberculosis,
Diabetes Mellitus, Organ Transplant Recipients, Those Who Are On Chemotherapy Or
Immunosuppressants, Prolonged Intake Of Steroids For Chronic Disorders Like Bronchial
Asthma, Rheumatoid Arthritis And Inborn Immunological Deficiencies. Neutropenic
Patients Are Prone To Develop Invasive Mycosis. Persons Who Have Undergone
Abdominal Or Cardiac Surgery And Those Who Received Repeated Intravenous Injections
Are At Risk Of Mycoses. In The Macroscopic Evaluation Of Tissue Specimens, Mycotic
Infections Are Frequently Mistaken For Neoplasms Or Other Diseases And A Mycosis Often
May Not Be Considered Until The Histopathological Examination Is Complete2.
There Are Four Basic Approaches To The Diagnonsis Of Mycotic Diseases: (1)
Clinical (2) Mycologic (3) Immunologic (4) Pathologic. Diseases Caused By Fungi May
Be Difficult To Distinguish Both Clinically And Pathologically From Those Caused By Other
Microbial Agents. Because Serological Test Have Certain Limitations And Have Not Been
Developed For Some Fungal Diseases, A Definitive Diagnosis Of Mycotic Disease Often
Rests On Direct Microscopic Demonstration Of A Fungus In Tissues And Exudates, Or On
Isolating And Identifying It In Culture. Histopathology Should Not Be A Substitute For
Mycologic Culture ; Rather The Two Should Complement Each Other Whenever
Possible.Histopathologic Evaluation Provides Indisputable Evidence Of Tissue Invasion
And Therefore Can Confirm The Pathogenic Significance Of A Cultural Isolate That Belongs
To The Body Flora Or That Is Usually Encountered As An Environmental Contaminant In
Culture. Histopathology Can Also Confirm The Presence Of Coexisting Infections By Other
Fungi, Bacteria, Viruses And Protozoans Thus Guiding The Clinician In The Selecting The
Most Appropriate Therapy And Management For The Patient. Although Some Fungi And
Related Organisms Can Be Detected In Hematoxylin And Eosin Stained Tissue Sections,
Special Histochemical Stains Are Usually Necessary To Demonstrate Their Morphology In
Detail. Fungi Can Be Adequately Detected In Cytologic Specimens Obtained By Fine Needle
Aspiration Biopsy, Brushing, Washing Or Scraping. A Drawback Of Cytologic Specimens
However May Be The Inability To Distinguish Invasive Fungal Infections From Fungal
Colonization1.
The Three Common Fungal Stains Used Are Gomori Methenamine Silver
(GMS)5,36, The Gridley Fungus (GF), And The Periodic Acid – Schiff (PAS) Procedures.
GMS Procedure Is Considered To Be The Best Of The Special Fungal Stains For Screening A
Tissue Section Because It Provides Better Contrast And Stains Fungal Cells That Are
Refractory To The GF And PAS Procedures.

Topic: Infectious Diseases and Mycology
Subfield: Small Animals
Field: Veterinary
Domain: Health Sciences