The study evaluates the morphology of frozen tissue sections treated by microwave-stimulated fixation compared with unfixed cryostat sections. Furthermore, microwave fixation has been compared with fixation at room temperature. Improved preservation of nuclear structures (chromatin pattern and nucleoli) was found with the microwave combination, while other parameters were indistinguishable from the unfixed cryostat sections. Fixation at room temperature showed no difference compared with the unfixed cryostat sections. The combined method might be useful in rapid diagnosis of mesenchymal tumors, lymphoid proliferations and tumors of the CNS.