Forensic Pathology and the Utilization of Histology: A Brief Review

Introduction

This article is a brief review of how histology is (or perhaps should be) employed in the work of forensic pathologists who perform autopsies in the various death investigation systems in the United States. The review includes information obtained from professional practice guidelines, standards, and other relevant reference sources. The review is not meant to be exhaustive but rather, a concise summary of issues and references.

The Issues

Even prior to 2011 and the current economic crisis which involves decreased funding of government-supported death investigation systems and medical examiner offices, there has been controversy about how histology should be utilized in conjunction with medicolegal autopsies. Some believe that histology should employed routinely in all medicolegal autopsies while others believe in a more selective approach. The concept of providing cost-effective services in the context of systems-based-practice and limited funding certainly raises the issue that a selective approach to histology might be adequate to meet public need and expectations without significantly sacrificing the quality of service. The discussion below addresses these issues.

Standards and Guidelines

The National Association of Medical Examiners (NAME) Forensic Autopsy Performance Standards contain only brief reference to histology. Sections G27 and G28 of the Standards require that the forensic pathologist have access to a histology services and that the forensic pathologist perform histological examination in cases with no gross anatomic cause of death unless the remains are skeletonized (1). According to this standard, histology would not be required in causes of death such as gunshot wounds, blunt force injuries, other traumatic injuries, and obvious natural causes such as ruptured aneurysms, coronary thromboses, well developed cardiac infarcts, fistulas from eroding tumors, hypertensive brain hemorrhages, and a variety of other natural causes with fairly obvious and conclusive gross pathologic changes.

Section D of The NAME Inspection and Accreditation Checklist (I&A Checklist) requires access to histology services, availability of routine special stains, and indefinite retention of microscopic slides when they are prepared. The I&A Checklist requires preparation, examination, and reporting of microscopic slides in all sudden infant deaths, and where feasible, in unexplained deaths and where necessary to establish a tissue diagnosis (2). Although it was probably not the intent, as written, the checklist would seem to require histology on infant deaths which are sudden but involve obvious or traumatic causes. Practically, it is probably within the spirit of the recommendation to limit histology to those infant cases in which the cause of death is also unexplained after gross autopsy. The I&A Checklist also seems to require histology to confirm the “tissue diagnosis” of perhaps incidental lesions such as possible renal cell carcinoma and others observed grossly. The I&A checklist requirements are consistent with the Forensic Autopsy Performance Standards in that histology is required in “unexplained” deaths which is similar to “no gross anatomic cause” and can also be considered to include cases with a possible toxicological cause of death. As with the Standards, the I&A Checklist does not require histology in cases of skeletal remains or other remains “not suitable for embedding or microscopy,” which would arguably include some cases of advanced decomposition and entail some discretion on the part of the forensic pathologist. It is important to reiterate that the I&A Checklist requires that when microscopic slides are prepared, they must be examined and a report of findings must be prepared. Section F requires that there is a written list/catalog of histology sections taken, designating the organ or anatomic site from which the section was obtained, and that diagnoses or conclusions arrived at by microscopic examination are included in the final autopsy report's list of diagnoses, summary of case findings, or opinion section.

One role for histology that is not mentioned in either the Standards or I&A Checklist is the potential role of histology in cases where attempts may need to be made to age or date an injury or finding such as a chronic subdural hematoma. Few would argue the potential value of histology in such cases, but it is worthy of note that this role was not specifically addressed in the Standards or I&A Checklist.

The now sunsetted College of American Pathologists (CAP) Practice Guideline for Forensic Pathology, originally published in 1998, states that “the extent of histologic examination of autopsy tissues is at the discretion of the pathologist (3).” For those who like firm rules by which to live, this guideline is not particularly helpful. The guideline does mention that histology can be useful to date injuries and to answer specific questions related to cause and manner of death. The need for histology in cases of suspected “sudden infant death syndrome” was also noted.

The 1994 CAP Practice Guidelines for Autopsy Pathology, also sunsetted, were written mainly for hospital autopsy practice, but contain some “options” for histologic examination (4). Recall that “options” are one of three “parameters” and that options allow for practice variation because of patient or physician-specific information (3). This is in contrast with standards from which variation is not expected, and guidelines which are recommendations that should accommodate only low level practice variations (3). The Autopsy Performance Guidelines state that “consideration should be given to histologic documentation of important grossly observed abnormalities,” and that “the number of blocks is based on pathologist judgment, objectives of the autopsy in a specific case, the practice of the institution, and the likelihood of future use of such specimens.” Fixation and storage was proposed as another option so specimens are available if the need arises, and a standard list of tissues suggested for collection was also provided. Finally, and importantly, the Autopsy Performance Guidelines state that pathologist discretion is permitted in the extent of histologic descriptions, and that a list of blocks may be included in the autopsy report. Again these guidelines were primarily for hospital-based practice, but some of the principles could carry over to the practice of forensic pathology.

The CAP's “Basic Competencies in Forensic Pathology” primer does briefly discuss histology (5). That publication acknowledges that “histologic sections are not necessarily taken in every medicolegal autopsy” (depending on the jurisdiction), but that “histology should be performed in each case where the cause of death is related to a pathologic condition,” and that histology can also be helpful to demonstrate such things as gunshot residue, soot, and iron. These recommendations, if followed, would require histology in cases with obvious anatomic causes of death such as coronary thromboses, ruptured aneurysms, hypertensive cerebral hemorrhages, and the like. Some would undoubtedly argue that histology is not needed in many such cases while others would argue that important underlying findings might be overlooked, such as a vasculitis resulting in thombosis. The primer also recommends that stock tissue be maintained in forensic cases for a minimum of one year, but it is not clear whether that constitutes a “requirement” to collect stock tissue on every case if histology is not performed.

The CAP Autopsy Performance and Reporting manual essentially restates the “options” discussed above from its Practice Guidelines for Autopsy Pathology (4, 6). The CAP Handbook of Forensic Pathology contains periodic reference to histology and its potential usefulness in cases such as suspected electrocution, but across-the- board recommendations for histology utilization are not presented (7).

It is not the intent of this article to review every proposed guideline or recommendation for collection of histology specimens in specific types of cases. Rather, the issue addressed herein is primarily whether and when histology should be performed. That being said, it is relevant to point out that numerous publications contain recommended lists of sections to be collected in specific types of cases, such as those for Sudden Infant Death Syndrome (8). Further examples from various texts and other resources are not included here.

Other Literature

In a prospective study of the value of histology reported by Molina, Wood, and Frost in 2007, the only published study of its kind, their conclusion was that “requiring histological examination in all cases of forensic autopsy is a waste of resources, both temporal and monetary” (9). The 189 cases they studied included only cases in which cause and manner death were easily determined from gross autopsy and histologic sections would not have been ordinarily performed. Thus, their study is not an indictment of histology in general, but supports the perception that histology is valuable only in selected cases.

Another issue is particularly relevant to medical examiner office with forensic pathology fellowship training programs. The Accreditation Council for Graduate Medical Education (ACGME) and Residency Review Committee (RRC) have requirements that forensic pathology fellows complete at least 200 complete medicolegal autopsies and that their required duties include review of microscopic findings with preparation of a written description of findings (10). As Molina and co-authors point out, however, it is not clear whether histology is required in every case performed by fellows, and they also point out that the education of forensic pathology fellows should include learning about when histology is helpful and when it is not. There is also the issues of systems-based practice and learning to operate cost-effectively. In the forensic pathology fellowship program at the author's place of work, fellows are taught to manage cases similar to the faculty in that histology is not performed in every autopsy case performed by a fellow.

Surveys

A recent survey about histology was conducted by Stephen Sgan on behalf of the National Association of Medical Examiners (12). The survey focused mainly on the pros and cons of in-house services versus outsourcing of histology services and, not unexpectedly, such decisions are often based on case load and budget considerations. The survey did not address the types of cases in which histology is performed by various offices.

The survey also showed that per slide costs ranged from $4.00 to $12.60 in off-site outsource situations (Median $7.00) and $4.93 to $27.09 (Median $11.25) when histology was done inhouse. None of the outsourcing centers reported additional costs due to courier or shipping. These price ranges overlap somewhat and it is not unreasonable to assume that centers at the higher end of the cost range may be more prone to limit histology to selected types of cases (especially if charges are made on a per-case basis), but the survey did not specifically address that issue.

Stock, Block, or Balk

When cases occur in which histologic sections may initially be deemed as unnecessary, one option is to process the tissue to paraffin blocks only and another option is to save stock tissue in formalin. A third option is to save no tissue at all. Paraffin blocks have the advantage of being easily stored in compact fashion but there is a cost to the production of the blocks. Saving stock tissue in formalin may be cheaper but does require more storage space, ventilation of formalin containers, and occasional refreshing of formalin in the stock containers. Saving no tissue at all is the least expensive in the short term but runs the risk of one being “caught between a rock and a hard place” if issues of histology come up at a later time and there are no tissues available for histology.

Examples from Personal Experience

At the author's place of employment, the office has an in-house histologist. In brief, the office policy is that tissue samples are collected on all autopsy cases and may be processed to blocks only, slides, or a combination of both. We do not routinely collect stock tissue because of storage issues, possible legal problems, and staff agreement that stored tissue is not needed routinely. Tissues are processed to slides when the autopsy shows no obvious cause of death (this includes suspected drug-caused deaths). Focal lesions, even if thought to be incidental, are processed to slides. In general, microscopic slides are also prepared in natural deaths even when the natural cause of death seemed apparent grossly. The autopsy report includes mention of the tissues examined and at least a brief report of relevant positive and negative findings. The office performs about 1000 autopsies per year and has a goal of averaging 8 tissue cassettes per case.

In regard to using histology in cases in which it may not have otherwise been used, two cases from the author's office serve as good examples. In one case, determining which of an anterior and posterior gunshot wound of the torso were the entry and exit wound was quite difficult. The bullet passed through the kidney and a sections of the wounds showed kidney cells in the posterior wound (apparently, the exit wound). In another example, a naked, burned, and embalmed body was found in the woods with an inconspicuous gunshot entry wound at the nape of the neck. Histology of the wound showed synthetic fibers probably arising from overlying clothing at the time of the shooting. There are many other similar examples, two of which include identification of pseudo-soot and identification of tissue in an exited bullet's nose to determine which organ the bullet passed through when multiple bullets had perforated the body.

Another case from the author's office shows the value of saving tissue when histology was not originally performed. A middle age man attempted a robbery and was subdued by witnesses. He had physical injuries and signs of compression asphyxia, and contrary to our usual procedures in such cases, histology was not initially performed. Subsequent testing showed hemoglobin AS. The blocks that had been saved were then processed to slides and extensive red cell sickling was noted in the sections. Sickle cell trait was included in the cause of death statement.

In the author's personal experience, paraffin embedded tissues have been used to conduct DNA profiling in cases of unidentified decedents whose deaths were investigated long before samples were routinely collected and preserved for DNA studies (i.e., from the “pre-DNA era”). In one case that was decades old, the body had been buried unidentified and the only samples from the victim were the paraffin blocks. However, in today's world in which samples for DNA testing are routinely collected and preserved, advocating the collection of histology samples for such purposes is undoubtedly outdated, unless some new or emerging technology in the future would make such samples potentially valuable for future genetic testing or other studies best applied to tissues.

If permitted by law, tissue obtained at autopsy can prove invaluable to researchers. Histology samples routinely taken by various medical examiners during their routine investigation of sudden unexplained infant deaths were used for subsequent study which showed that pneumocystis elements were found in sudden infant death cases, shedding possible light on the life cycle of the pneumocystis organism (11). It must be noted, however, that many medical examiner offices cannot take tissues solely for research unless some type of informed consent is employed. In Georgia, for example, the death investigation statute restricts tissue retention to the purpose of determining the cause and circumstances of death. The possible future use of histological samples for research probably should not be used as a reason for taking them during a routine death investigation case, and histology policy should probably be based primarily, if not solely, on everyday death investigation needs.

One could argue that because the vast majority of the approximately 210,000 autopsies now conducted in the United States (13) are done in the medical examiner/coroner office setting, that there is a societal obligation to collect histology samples which may be used for various types of research formerly conducted by academic pathology department autopsy services. Although such studies might facilitate monitoring of the ongoing health of the nation, that argument would probably not persuade government funding entities to support such a practice. Special projects, perhaps funding of histology by the National Institutes of Health, for example, might be worthy of further consideration to facilitate autopsy-based tissue research projects which go beyond routine daily death investigation needs.

Until recently, the organ and tissue procurement agency which does procurements on cases managed by the author's office required histology on tissue donors (not organ donors) comparable to that done in a hospital autopsy setting. Now, after review of its data, the agency concluded that histology was not cost-effective and that there were virtually no cases in which histology changed its decision making process. Thus, we now process tissues to blocks only in tissue donor cases (when histology is not needed for other reasons) so if an issue surfaces later, tissue is available to examine.

Finally, some forensic pathologists are certainly more timely in completing their cases than others, and for those who work in offices with high autopsy case load, timely completion of cases can be challenging. Having to review and report on microscopic sections which are questionably relevant to a case may be counter-productive. This problem gets to the issue of having histology policy which at least takes into consideration the “practice of the institution” as mentioned earlier (4).

Conclusions

Based on the information described above, and recognizing that the various guidelines and standards have been prepared in consensus by committees, it seems reasonable to suggest the following practices concerning histology:

The author believes that the above approach is prudent and unlikely to result in unnecessary preparation of microscopic slides or overlooking of potentially relevant findings. The above approach assures that tissues are available at least in the short term if blocks or slides are not prepared initially. As a minimum measure of compliance with published standards, the forensic pathologist should perform histological examination in cases with no gross anatomic cause of death unless the remains are skeletonized (1).