Chapter 6: Specimen Preparation

INTRODUCTION

What happens to a skin excision specimen after it disappears out of the operating room is a mystery to many surgeons. But some surgeons realize that a basic understanding of pathology is often needed to make informed surgical decisions. And some surgeons (usually dermatologists) are so interested in the pathology processing that they take on the role of the pathologist themselves.

SPECIMEN ORIENTATION

There is tremendous variation in how specimens are orientated when they reach the laboratory. Communication between the pathologist and surgeon is key in arriving at a satisfactory protocol to allow uniformity in processing. Larger specimens are often orientated with the placement of sutures, but a simpler option is the cutting of small notches by the surgeon (as outlined in Chap. 5). A single orientation at the top of the specimen is generally sufficient because once you know where superior is, then inferior, medial, and lateral can be deduced. Where precise mapping is more critical, more than one notch or suture may be used for orientation.

INKING

The specimen is inked using Indian ink and this information is drawn on a corresponding map. Inking can be done by the surgeon in the procedure room or by the pathologist or histotechnician (Fig. 6.1). Some surgeons prefer to do the inking in the procedure room to reduce the chance of placing ink on the wrong margins.

The processing technique chosen will determine the inking method. Anywhere from one to eight colors may be used. Whichever method is chosen, it needs to be understood that the expectation of the inking process is that it will permit the localization of any positive margin microscopically so that positive margins can be located and re-excised on the patient.

Care needs to be taken not to use too much ink as the ink may inadvertently bleed and confuse the margins. The same problem can also occur if the specimen is too wet. The quality of the ink is also important, as poor-quality ink may wash off during the tissue preparation.

SIX MAIN SPECIMEN PROCESSING TECHNIQUES

Though there are further permutations, the main aspects of processing skin specimens for margin control surgery (MCS) can be boiled down to six distinct methods. Deciding which one to use depends on the size of the excision, the pathology, and the preference of the staff involved. It is important to mention that all these methods can be performed with intraoperative frozen sections or formalin-fixed paraffin sections (slow Mohs).

The Bread Loaf Technique (Serial Transverse Vertical Cross-Sections)