Optimal formalin fixation and processing schedule of cell blocks from fine needle aspirates.

In fine needle aspiration cytology, cell blocks may provide diagnostic information complementary or additional to that obtained from examination of cell smears. However, the morphological preservation is often unsatisfactory in cell blocks processed by routine schedules used for surgical specimens. This study investigates the effects of different formalin concentrations and processing schedules on cellular morphology. We conclude that 7.5% buffered formalin is the optimal formalin solution and a shortened processing time through xylene is desirable.