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chapter 2: Sample Acquisition, Processing, and General Diagnostic Procedures
save the inevitable waste of precious material at each new cutting session, unnecessary cutting may be done and may raise issues related to the storage of cut sections (Figure 1).
Common procedure to date
H & E staining for histologic diagnosis Repeat sectioning
For IHC Repeat sectioning
For molecular testing
The procedure in era of molecularly targeted drugs
H & E staining for histologic diagnosis For IHC
For molecular testing
Figure 1. Preparation of tissue sections during diagnostic workup. Current routine practice involves making additional sections for IHC assay and/or molecular testing after the initial sectioning and hematoxylin and eosin (H & E) staining for histologic diagnosis. Multiple sequential sectioning may deplete the tumor volume each time block trimming is necessary. In the era of molecularly targeted therapies, the preparation of additional unstained sections for possible IHC analysis and/ or molecular testing may significantly reduce the amount of tissue sample lost and improve turnaround time.
The first step in the evaluation of a sample is to identify the presence or absence of malignancy. Depending on patient selection, choice of sampling technique, and operator skill, the rate of positive tumor findings is generally high but may range from approximately 60% to more than 90% (Schreiber 2003). It is well recognized that, even when tumor is present in the sample, it may not be present in all tissue fragments and it generally comprises a small proportion of the tissue submitted (Coghlin 2010). Once malignancy is confirmed, the next step is to exclude the possibility