Three simple techniques allow rapid examination of biopsy material during surgery: touch preparations, squash preparations, and the smear (Figure 2-1). Although the main emphasis of this text is using smears, the other techniques are important to mention.

In some very discohesive lesions, merely touching the tissue to a glass slide releases diagnostic cells. Such lesions include abscesses filled with neutrophils and loosely structured tumors such as adenomas, lymphomas, and some carcinomas. This technique is fast and, compared to the other two methods, is gentle on the cells. With small specimens, touch preparations require handling the tissue with forceps, which could be problematic when the tissue is extremely soft. However, in appropriate cases, touch preparations produce excellent cytological details and a rapid, accurate diagnosis. The main drawback of this technique is obtaining cells from more cohesive lesions, in which the cells bind more tightly to their matrices. Many gliomas, reactive processes, and metastatic tumors are loath to so easily give up their progeny to the glass. Like many aspects of pathology, in which artifacts are useful to distinguish diseases, a process that refuses to yield cells in a touch preparation gives some additional information. For example, in a routine touch, a pituitary adenoma will easily shed its cells in abundance, whereas inflammatory lesions and normal pituitary remain defiant.

The next level of vigor in affixing cells to glass slides is the “squash” preparation. Here, tissue is crushed between two slides and then stained. Similar to touch preparations, this method will give excellent cytology, although now the cells may show some crush artifacts. As the tissue spreads out under the force produced by the two glass slides, its structure partially breaks down, thereby releasing more cells. Notably, neoplastic cells that elaborate their own matrix will retain their relationship to this milieu on the slide. Gliomas in particular are especially revealing using this technique. The largest difficulty with such preparations is that they leave a big glob of tissue in the center of the slide. These central mountains are often too thick to be useful under a microscope. Both squashing the tissue and pulling it apart to make it thinner converts the squash preparation into a smear.

Unlike touch and squash techniques, a smear requires a bit more finesse and experience to optimize (Figure 2-2). The following is a detailed description about how to produce the best smear and what can be gained by doing so.