The preanalytical process in surgical pathology begins when the specimen is received in the frozen section or histology laboratory , and is accessioned into the laboratory information system. The first opportunity for specimen mishandling, and therefore the error, is in the operating room, physician office, interventional radiology or endoscopy suite from which the specimen arises. The practice of preparing specimen containers and labels prior to a procedure is common, and therefore, there is significant opportunity to pair a specimen from patient B with the labels from patient A who was previously in that room. One study from a large surgical service documented an error rate of 4.3/1000 specimens with unlabeled specimens, empty containers, incorrect laterality or tissue site, incorrect patient, no patient name, and no tissue site identified representing the most common errors [27]. While it is possible to effect error reduction through strict adherence to a policy that requires a matching of two patient identifiers at every step of the process and accountability in the form of requirements for provider initials on the specimen container to verify proper identification and the presence of tissue in the container, in reality these processes are beyond the control of the laboratory [28]. Therefore, the true opportunity for error reduction begins at the time of accessioning .

When specimens are received in the laboratory, the specimen identification on each container should be rigorously matched with the specimen requisition , with confirmation that there is a match in the patient using two patient identifiers and an exact match in the specimen source. Failure to do so introduces an opportunity to assign one or more specimens to the wrong patient, a serious error if a malignant diagnosis is involved. Similarly, if the accessioning personnel do not carefully match the patient name and a second identifier, typically date of birth or medical record number, it is possible to erroneously accession the case to the wrong patient, one who shares a name with the index patient. When the accessioning is complete, there should be a unique case number associated with specimens from one patient as well as a unique alphanumeric designation for each part of that accession. For example, a uterus with separately submitted adnexa might be accessioned as S-year-unique number (e.g., S-13-4506) with parts A (uterus), B (right fallopian tube and ovary), and C (left fallopian tube and ovary). Another opportunity for error exists when the specimens are not correctly matched with the alphanumeric designation.

The next step in the process of accessioning is the labeling of tissue cassettes. There are three essential elements to a cassette label: the case number, the alphanumeric designation of the specimen, and a sequential label for each cassette within that specimen. The latter should then be specifically identified in a gross description. For example, a cassette labeled S-13-4506 A1 in the example above might contain sections of uterine cervix while S-13-4506 A2 might contain a section of uterine serosa, and S-13-4506 B2 a section of fallopian tube. Incorrect cassette labeling, with a failure to detect the error at the time of tissue submission, can result in an incorrect diagnosis, when, for example, cassette A1 in a cancer resection contains a surgical margin and cassette A11 does not.

Perhaps, the greatest opportunity for error is in the process of submitting tissue for microscopic examination (“grossing”) . The prosector could potentially: (1) erroneously submit tissue in a cassette belonging to a different patient (tissue from case 4506 submitted in a cassette labeled 4507), (2)submit tissue in the wrong cassette within a case (in the example above, the margin is submitted in A11 instead of A1), or (3) inadvertently submit extraneous tissue . The latter typically occurs when the prosector is submitting tissue from more than one case at a time, or when the workspace and instruments have not been adequately cleaned after each accession, providing an opportunity for inadvertent tissue carryover from case to case. Finally, error can occur as the result of inadequate dictation of the macroscopic findings as they relate to the tissue cassettes submitted. Common errors in this category are failure to unambiguously identify each of the surgical margins with ink of a designated color in cancer resection cases, and failure to provide a “section code” that links each tissue cassette submitted to a particular tissue site or lesion.

After the process of specimen grossing and tissue submission, tissue cassettes are processed through dehydrating solutions and paraffin. In most laboratories, this is accomplished by automated tissue processers that are driven by a user-defined processing schedule. The paraffin-impregnated tissues are then re-embedded into the same tissue cassettes in which they were submitted, with additional paraffin as needed, in order to provide a tissue surface that can be subsequently trimmed and sectioned by the histotechnician performing microtomy. With the increasing number of multi-site laboratories, it is increasingly common for tissue cassettes to be transported to a core laboratory for processing. There are three major opportunities for error in these processes: (1) tissue is lost, either a portion of tissue within a single cassette or one or more tissue cassettes in their entirety, (2) tissue cannot be adequately examined microscopically due to inappropriate tissue processing, and (3) extraneous tissue (i.e., tissue from another patient) is introduced inadvertently. In general, tissue cassettes are fenestrated, with parallel slits or small, round holes that allow processing fluids to flow freely through the cassette. Although these fenestrations are of small diameter, it is theoretically possible for minute tissue fragments to flow into or out of a cassette during processing, leading to a loss of tissue or gain of extraneous tissue fragments. Much more commonly, however, these misadventures occur at the time of embedding , when the embedding personnel do not carefully observe the number of tissue fragments to be embedded, work on more than one case at a time, and/or do not rigorously clean the embedding forceps between cases. Tissue processing is beyond the scope of this discussion; however, for purposes of error reduction the avoidable sources of error leading to loss of tissue integrity, and therefore, the potential for an erroneous interpretation due to poor visualization of microanatomy, include: (1) submission of tissue of inappropriate size, (2) inadequate time in formalin fixative prior to processing, and (3) failure of personnel loading the tissue processers to recognize that a tissue is of inappropriate type for the processer onto which it is loaded (e.g., a small biopsy processed using a schedule intended exclusively for large tissues).