Preparation of Formalin-Fixed Paraffin-Embedded Tumor Samples: A Protocol to Preserve Tissue and Cytology Samples from Non-small Cell Lung Cancer (NSCLC)

- To begin, obtain lung tumor specimens as tissue samples or as cytology samples from bronchial washes-- a saline wash containing cells from the inside of the airways. To prepare tissue samples, transfer freshly dissected lung tissue into an embedding cassette. Fix and preserve the tissue with the appropriate concentration of formalin.

To prepare cytology samples, first, treat bronchial washes with DL-dithiothreitol for homogenization. Centrifuge and remove the supernatant. Next, treat with a mucolytic solution to liquefy mucus and separate the cells. Centrifuge to pelletize the cells and fix them with formalin. Treat cells with a suitable cell block preparation reagent to concentrate the sample while working with small pellet volumes.

Transfer the pellet into an embedding cassette. Process both sample types by dehydrating them through a series of graded alcohol baths. Remove alcohol using an appropriate clearing agent followed by wax infiltration. Embed the cassette in liquid paraffin wax and allow it to solidify. This forms a layer around the tissue, holding the specimen in place.

Use a microtome to obtain thinly sliced sections. Place the sections on positively charged glass sli