Preparation of Cell Blocks from Cytology Samples with a Predominance of Individually Scattered Cells

Reference: https://app.jove.com/t/1316/cell-bloc...
The process of creating cell blocks from cytology samples that contain mostly individually scattered cells involves several steps.

First, the cytology sample is collected, typically through a fine needle aspiration or a brush biopsy, and prepared on a glass slide. This involves spreading the sample evenly across the slide to ensure that all cells are represented.

Next, a fixative solution, such as formalin or alcohol, is applied to the slide. This fixative solution serves to preserve the cells and prevent any further degradation. It works by cross-linking the proteins within the cells, effectively "freezing" them in their current state.

After fixation, the slide is washed to remove any excess fixative. This step is important to ensure that the fixative does not interfere with subsequent processing steps or staining procedures.

Next, a thin layer of agar is applied to the slide. Agar is a gelatinous substance derived from seaweed that solidifies when cooled. By applying agar to the slide, the cells are embedded within a more stable structure, making it easier to handle and process them.

Once the agar has solidified, the slide is immersed in a decalcifying solution. This step is particularly important when dealing with samples that may contain calcium deposits, such as bone or calcified tumors. The decalcifying solution works to dissolve and remove these calcium deposits, which could interfere with subsequent processing steps.

Finally, the slide is dehydrated, cleared, and embedded in paraffin wax. Dehydration involves removing the water from the cells, typically through a series of alcohol washes. Clearing involves replacing the alcohol with a substance, such as xylene, that is miscible with both alcohol and paraffin wax. This step ensures that the cells are properly prepared for embedding.