Guidelines for the Dissection of Head and Neck Specimens

Introduction

Head and neck specimens are technically difficult because they often comprise a lot of different anatomic structures and corresponding surgical margins. In the following text, some practical guidelines are given that may be useful when confronted with these specimens. The following specimens are discussed:

• Oral cavity : lip, tongue, floor of the mouth, and mandibular gingiva, mandible, maxilla, and cheek

• Oropharynx : tonsillar area, base of the tongue, and soft palate

• Larynx : endolarynx and hypopharynx

• Sinonasal region : maxillary sinus

• Salivary gland : parotid gland

• Neck dissections

• Thyroid gland

General Remarks

Dissecting head and neck specimens serves several aims: first, confirmation of the diagnosis made preoperatively, either cytologically or histologically; second, the pathologist frequently has to assess the status of the surgical margins; third, the pathologist has to confirm the tumor size and extent, and the involvement of adjacent structures as determined by preoperative diagnostic imaging. The third aim is best served by choosing a plane of dissection that runs parallel with one of the planes used for imaging. Maintaining a plane once chosen is of the utmost importance. Changing the plane of dissection will jeopardize adequate reconstruction of the three-dimensional structure of the specimen. Taking photographs of the specimen and its slices will be very helpful.

Actual dissection starts with identifying the specimen, the various structures that form part of it, whether it comes from the right or the left side, and whether there is any gross tumor visible at the outer surface. If there is, the gross appearance is recorded as well as the anatomic surface where the lesion is located. Moreover, its size is measured in two dimensions. Slicing of the specimen should be done perpendicular to a natural mucosal surface. The thickness and number of slices obtained should be recorded. It should also be noted in which slices tumor is present; in which slice the tumor reaches its greatest thickness, which also should be recorded in millimeters or centimeters; and in which slices the tumor comes closest to the surgical margin. It should also be mentioned which margin this is and the distance should be given in actual centimeters or millimeters. Slicing usually can be done with a sharp knife, but in the case of specimens containing bone such as the maxilla or mandible, or cartilage such as the larynx, specific apparatuses such as a commercial meat slicer for the larynx or a water-cooled diamond saw for the bone are indispensable. Putting the whole specimen in a decalcification solution to allow sectioning with the knife should be discouraged. The quality of both macroscopic and microscopic features is often suboptimal. However, if this is the only method available, then the decalcification process should be carefully monitored to avoid overdecalcifying the specimen.

Specific Features

Oral Cavity

Lip

Tumors most often involve the lower lip. They lie at the border between the skin and mucosal surface, the so-called vermilion border. Specimens most often consist of a wedge-shaped excision, a triangle with the epidermal-mucosal junction as base. These specimens should be sliced perpendicular to the vermilion border, going from one side to the other ( Fig. A1.1 ). The cut surfaces of the slices allow assessment of tumor size and thickness, as well as distance to the margins.

Tongue, Floor of the Mouth, and Mandibular Gingiva

Tumors at these three sites are discussed together, as they occur in adjacent areas, and the way to handle these specimens is the same for all of them. In all cases, the specimen is sliced parallel to the frontal plane in a mediolateral direction. If tumors are located at the lateral border of the tongue and the floor of the mouth, the mandible is mostly left in situ. Then, slicing can be done with the knife. If, however, the tumor lies more laterally in the floor of the mouth, encroaching on the mandible or even involving it, a part of the mandible is included in the specimen and has to be sliced as well ( Fig. A1.2 ). In cases of mandibular gingival cancer, the adjacent part of the mandible is always removed. Assessment of the slices regarding tumor size and extent should be performed, and tumor thickness and distance to the margins recorded. If there is mandibular bone included, the pathologist should pay close attention to the relationship between tumor and bone. Involvement of mandibular bone is difficult to assess preoperatively, and the surgeon may like to know whether it was indeed necessary to remove a part of the mandible. One should also note whether the removed bone consists of the full height of the mandible or only the alveolar process. Especially in patients whose teeth are still in place, the height of the mandible allows this latter procedure. Then, a horizontal osteotomy plane forms an additional resection margin for evaluation.

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