Slides & Blocks

Blocks and slides are how tissue samples are prepared for microscopic examination. Tissue is fixed, embedded in paraffin to make a block that preserves structure; thin sections are cut from the block and mounted on glass slides, then stained to reveal cells and patterns. Pathologists use blocks for long-term storage and slides for diagnosis, special stains, or molecular testing.

A biopsy slide is a glass plate holding a very thin section of excised tissue that’s been fixed, embedded, sliced, mounted and stained for microscopic examination. Pathologists study the cells and tissue architecture on the slide to diagnose cancer, inflammation, infection or other disease. Slides are preserved as a permanent record and can be used for special stains, immunohistochemistry or molecular tests.

A tumor block is a paraffin‑embedded tissue specimen taken from a biopsy or surgical resection that contains tumor. Pathology cuts thin sections from the block for microscopic review, immunohistochemistry and molecular tests to determine cancer type, grade, margins and biomarkers. Tumor blocks and slides are archived for diagnosis, additional testing, second opinions and future treatment planning.

Biopsy slides can remain readable for many years—often decades—if stored in cool, dry, dark conditions. Clinical retention policies typically keep slides about 10 years for adults and longer (often 25–30 years) for children; paraffin blocks can be preserved even longer. Staining may fade over time, but new sections can usually be recut from stored tissue blocks for future testing.

Slides are thin glass or plastic supports used to hold biological samples for light microscopy. They allow specimens to be spread, fixed and stained so cellular structures, microbes or blood components are visible and preserved. Slides enable standardized magnification, cell counting, morphology assessment and detection of pathogens, supporting accurate diagnosis, monitoring and research in clinical and laboratory settings.

Carry biopsy slides in their original labeled slide holder or a rigid, cushioned slide box to prevent breakage. Keep slides upright, avoid extreme temperatures, moisture, direct sunlight and vibration. Handle slides by the edges or wear gloves; never touch the specimen area. Include required paperwork and patient identifiers to maintain chain of custody. Transport by hand or reliable courier and deliver to the pathology lab promptly.