Spontaneous Clots in Body Fluids: Can They Cell Block?

Summary: Introduction: Cell blocks have become a critical component in the diagnostic and prognostic analysis of cytologic specimens. Yet, it is common for cell blocks to lack sufficient cellularity for assessment and ancillary testing. Assessing cellularity in spontaneous clots that form in body fluids can aid in improving cell block utilization. Materials and Methods: Eighteen body fluid specimens originally submitted for cytologic evaluation were selected for processing. For each fluid, two cell blocks were made, one using the spontaneous clot (SC) and one using the cell pellet (CP) from only the concentrated fluid. A hematoxylin & eosin-stained (H&E) slide for each block was assessed for cellularity and ranked on a scale from zero to three. A score of zero represented no cells present, while a score of three represented abundant cells of interest present. Results: For the CP blocks, 28% had a cellularity score of 0, 44% had a score of 1, 11% had a score of 2, and 17% had a score of 3. For the SC blocks, only 6% had a cellularity score of 0, 39% had a score of 1, 28% had a score of 2, and 28% had a score of 3. Conclusions: Cell blocks prepared using the spontaneous clot method resulted in an overall higher cellularity compared to the CP blocks. The SC blocks prepared from malignant fluids also showed denser areas of pure tumor nuclei. This resulted in adequate spontaneous clot blocks for genomic testing, while the corresponding CP block was only adequate for diagnostic purposes.