By prof. Matti Kiupel BS, MS, PhD, DACVP

Mammary gland multifocal lobular hyperplasia secondary to mushroom supplements

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The goal of histologic examination of tumor biopsies is to provide an accurate diagnosis and prognosis of a neoplastic entity and, in the case of excisional biopsies, to evaluate cleanliness of surgical margins. The assessment of tumor excision status (‘margins’) is fundamental to the treatment and management of clinical oncology patients as it helps to determine whether there is local control or the likelihood of recurrence.

Assessment of surgical margins is a challenging task for the clinician, histology technician, and pathologist. It is an imprecise process, and there are nuances of margin evaluations that are difficult to understand for the untrained veterinarian. Good communication between the pathologist and surgeon will greatly improve the information provided and ensure that the samples are evaluated considering the surgical intent. It is as difficult for the clinician to communicate to the pathologist the location of a mass and how it was excised and which surgical margins are of concern as it is for the pathologist to communicate to the submitting veterinarian the results of a margin evaluation in a written report, or even by phone. Ideally, the surgeon takes into account previous cytological or histological diagnosis, location in the body, proximity to vital structures, extent, availability of skin to close an incision and presence of a fascial plane in determining the type of surgery. The evaluation of histological margins varies with surgical approach, type of margin identification(inking, sutures), and tissue shrinkage related to post-surgical contraction, fixation, processing and trimming procedures. Additionally, neoplasms have unique characteristics, thus growth habits and natural history are important to determine the appropriateness of reported margin measurements.

The surgeon should always provide a description of the intent of surgery (i.e., incisional or intracapsular biopsy versus excisional with either marginal, wide or radical excision) and indicate any specific questions or areas of concern. As an example, there is no point in reporting margins of incisional(intracapsular)biopsies or debulking surgeries as there was never a curative intent. Margins should be reported if there is curative intent, regardless of the type of surgery.

Accurate margin assessment is further complicated by the various techniques applied in different laboratories to evaluate margins. To overcome the later problem, AVD offers a standardized approach to margin evaluation for routine submissions and a more detailed approach for determining complete excision for neoplastic entities where such knowledge impacts the therapeutic approach, e.g. mammary tumor, melanocytic neoplasms etc.

The first part of this article will provide detailed information for the clinician on how to ink and identify surgical margins, while the second part will explain how surgical margins are evaluated in the laboratory and what results the clinician can expect from the biopsy report.

To correctly identify surgical margins during the trimming process in the histology laboratory, it is necessary to paint (ink) the surgical margins. This can be done by the submitting veterinarian on unfixed samples or in the laboratory after the samples have been fixed. It is often an advantage for referring veterinarians to ink the margins on an unfixed tissue because they have performed the surgery and can best identify the margins of concern. The following paragraphs and figures illustrate how clinicians can ink samples before submission, especially if there is a specific margin that is of particular concern. By inking the tumor margins the clinician can guide evaluation of certain regions and ensure examination of these surgical margins.

Keywords: inking margins, singular histopathology case, tumor biopsies, histology laboratory