HISTO is a mnemonic that provides a clear framework for analyzing slides:

H – Hierarchy of Magnification

• Start broad: Use low-power magnification (4x–10x) to examine the overall tissue architecture.

• Identify abnormalities: Look for patterns (nodular, diffuse, infiltrative) and locate areas needing closer examination.

I – Integrity and Orientation

• Confirm that the tissue section is intact, properly oriented, and free from artifacts.

• Check for completeness of margins, if relevant (e.g., in excisions or biopsies).

S – Structures and Stroma

• Structures: Evaluate specific components like epithelium, glands, blood vessels, and ducts.

• Stroma: Assess connective tissue for fibrosis, inflammation, edema, or necrosis.

• Compare abnormal areas with normal counterparts.

T – Tissue Details (High Power)

• Zoom in (20x–40x) to analyze cellular features:

• Nuclei: Check size, shape, chromatin pattern, mitotic activity.

• Cytoplasm: Evaluate for inclusions, granularity, or vacuolation.

• Abnormalities: Look for dysplasia, atypia, or malignancy.

O – Overall Correlation

• Synthesize findings into a cohesive picture:

• Relate histologic changes to clinical and gross pathology data.

• Formulate a differential diagnosis or definitive diagnosis.

• Consider additional stains (e.g., immunohistochemistry) if needed.

We will use this method throughout the course.