Since 1971, EPL has developed and refined methods to provide high quality and efficient histopathology services. The following information details some of the steps taken during histology processing and preparation at EPL, to ensure tissue accountability and define routine tissue recut procedures.
Tissue Accountability on All Studies:
Each study received at EPL will be assigned specific trimming and blocking instructions. These instructions will include those described in the study protocol and/or EPL’s SOP for trimming (based on RITA guidelines), unless otherwise requested.
An Individual Animal Worksheet (IAWS) will be created to document all phases of histology. In addition, recut sheets (block and wet) will be prepared, if necessary. All documentation is provided with the prepared slides, and these documents provide information to detail the steps taken during the histology preparation.
At the start of trimming, a project observation note (PON) will be created to indicate how tissues were submitted and presented for processing (thymus, pituitary, adrenals, lymph nodes, thyroids, or other small tissues in cassette; labeled or not). The PON will also indicate if wet recuts will be possible or if all tissue received is submitted for processing at initial trimming. The information on the project observation note serves as a valuable resource to technicians at time of microtomy, embedding, and microscope checkout.
Routine tissues not present in wet tissue will be verified by a second technician and documented on the IAWS. Furthermore, all lesions documented at the time of necropsy will be submitted, if requested by protocol. If a noted lesion is not present in the wet tissue, absence will be verified and documented on the IAWS by a pathologist, rather than a technician.
Lesions identified at trimming will be described and submitted for processing.
At the time of embedding and microtomy, technicians will review documented lesions and trimming comments to ensure proper embedding orientation and sectioning (e.g., step sections).
Blocks and slides are organized, matched, and presented to checkout technicians. A 100% microscopic check is performed on all slides to evaluate quality and tissue accountability.
General Criteria for Return to Wet or Block for Missing Tissues:
EPL SOP does not require recuts from wet or block for mammary gland in males if the section submitted appears to be the mammary region.
Rodents 53 weeks of age or greater will not have recuts for thymus if mediastinal tissue is present on the slide.
Several step sections are presented at the time of microtomy for parathyroids and optic nerves. If one (1) parathyroid or optic nerve is present, a recut will not be attempted if the technician determines, after the review of slide and block, that a recut will not be successful. We consider the multiple step sections and rigorous checkout procedures to have completely satisfied all attempts to have both parathyroids achieved in section, and further recut requests by an offsite pathologist should not be necessary in most cases.
In individual cases where a tissue may be absent but is present for the majority of animals on the study, the technician will judge whether wet or block recuts should be requested for the individual tissue absence. Examples would include areas of stomach (pyloric), optic nerves, or mammary gland for males.
Following these procedures should ensure all possible tissue is presented for pathology review and will eliminate delays due to the pathologist’s need for recuts.