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Histology FAQ
Histology FAQ


Is prolonged time in fixative bad for the specimen?

Depends. If you plan on only performing H&E or simple dye staining on the specimen, then no, prolonged fixation will not harm the tissue. But if you plan on performing immunohistochemical staining on the specimen, prolonged exposure to fixative can hinder the quality of IHC staining. To minimize this, transfer the fixed specimens to 70% alcohol.

How quickly is tissue “fixed” once it’s placed in 10% formalin?

Once again, the answer is “depends”. Fixative takes much longer to permeate firm tissue (such as uterus) or encapsulated tissue (such as kidneys or lymph nodes) than loose or hollow structures. For quicker fixation, large, solid organs should be “bread-sliced” (multiple incisions every few centimeters) and placed in 10-times its volume of fixative. As a very general rule, formalin penetrates at approximately 1cm per hour at normal atmospheric pressure and at room temperature. Here is a good article on the subject: http://www.histosearch.com/ADP12HowMuchFormalinIsEnough.pdf

Can you perform an Oil Red O (or any other stain for fat) on a paraffin processed tissue?

During routine paraffin processing, tissue is exposed to alcohol. Alcohol dissolves adipose (fat) tissue. On H&E-stained sections, adipose tissue appears as large, hollow, un-stained cells. This is because only the cell membrane retains the stain. The fat is no longer there and does not stain. The Oil Red O stain will only work on frozen sections, since this tissue has never been exposed to alcohol.

Why do you require a specimen manifest with each order?

A neatly typed and organized specimen manifest helps us in many ways. All specimens are matched up to the manifest and any discrepancy is immediately taken care of by notifying the client that one or more specimen is missing. Also, many specimen containers are labeled by handwriting which of often illegible. A typed manifest allows us to verify the questionable labeling. Lastly, slides and slide labels are made using the manifest. When the order is completed, there should be no orphaned slide or paraffin block. If there is, than a full investigation is initiated to find out why there is a discrepancy.

Will sending specimens for a Saturday delivery speed up my turn-around?

Probably not. Specimens are logged in Monday through Friday, so any specimen arriving on a Saturday will sit in receiving until Monday anyway, so save your money and have your specimen delivered on Monday.

What is the turnaround time for histology orders?

Orders are placed in different queues depending on the type of request and then processed on a first come first served basis. RUSH orders always have the fastest turnaround. PRIORITIES are completed after all RUSH orders are completed but before any ROUTINE orders are started. ROUTINE orders are worked on only after all RUSH and PRIORITY orders are completed. As a very general rule, RUSH orders are completed in a few days, PRIORITY orders are completed within two (2) weeks and ROUTINE orders are completed within four (4) weeks. Turnaround time also depends on the number of specimens per order and the number of research orders already in the queue.