Cell tube block: A new technique to produce cell blocks from fluid cytology samples

Background: Cell blocks are widely used in human cytopathology. Several techniques have been proposed to convert fluid specimens into solid material, which after embedding in paraffin can be used for histochemistry, immunohistochemistry, or molecular testing. In contrast, only in the last few years, have cell blocks begun to be used in the veterinary field. Objectives: The purpose of the study was to present the production and features of cell tube blocks (CTB) with veterinary liquid samples. Methods: Liquid samples including cerebrospinal fluid, cutaneous cyst fluid, pericardial and pleural effusions, bronchoalveolar lavage, urine, and blood were centrifuged in a microhematocrit centrifuge. Capillary tubes were broken at the liquid-solid interface and fixed in 10% formalin for 24 hours. After paraffin embedding, sections of CTB were used for different stains including immunohistochemistry. Results: The morphology and cellular detail in CTB sections were comparable to conventional histologic sections and other existing cell block techniques. The use of special stains such as Gram, Giemsa, alcian blue, and periodic acid-Schiff was straightforward, and immunohistochemistry results with antibodies to pan-cytokeratin, PAX-5, and CD3 were considered good. Conclusions: The CTB method was easily implementable under practice conditions (up to the fixation of the microhemtocrit tube), analogous to surgical biopsy submission for histology. Cell tube blocks can increase diagnostic accuracy when the technique is used in tandem after the cytologic evaluation, and the technique allows storage of fluids. Other advantages of CTB were the simplicity, low cost, and separation of erythrocytes from the nucleated cells, which was helpful in hemodiluted samples.