Technique

To obtain the maximum amount of information from the frozen section biopsy, the tissue orientation must be accurately known. First, the pathologist must be familiar with ophthalmic/orbital tissues so that the identification of the tissue types (conjunctiva, lacrimal gland, lacrimal sac, etc.) does not present any difficulty. A critical step in tissue orientation is communication between the surgeon and the pathologist. It is beneficial if clinical information and intraoperative findings are shared with the pathologist; even better, the pathologist can physically walk into the operating room to observe the procedure and specimen collection as a means of orienting himself or herself to the anatomy and gross pathology. It is also helpful in many instances for the surgeon to walk to the laboratory and examine the frozen section specimen with the pathologist. This communication also is very useful to decide on further pathological procedures (e.g., molecular genetic studies or immunohistochemistry) and to ensure that the pathologist apportions the specimen accordingly. If there is any shortage of tissue, this advice could be relayed to the surgeon while the surgical field is still open. In complicated cases, particularly in recurrent tumor excisions, it is helpful if the pathologist can study the histopathologic sections obtained prior to the frozen section. For reporting purposes, direct communication via telephone or intercom is ideal; however, if the patient is under local anesthesia, communication by intercom should be done discreetly.

No fixative is needed for frozen section specimens; tissue should be placed on a piece of cardboard or gauze and kept wet with a few drops of saline or borate-buffered saline prior to delivery to the frozen section laboratory. In frozen sections intended for ex-cisional margin analysis, labeling of tissue should be done meticulously and immediately at the time of excision. The tissue specimen from the margin may be placed on a piece of cardboard with its excision margin facing down. The direction of the excision margin should be clearly written on the requisition slip to guide the pathologist in determining the proper orientation. A simple diagram drawn on the same piece of cardboard helps to orient the pathologist.34

The conventional approach to excisional margin analysis is to remove the tumor and label the speci-

MEDIAL

MEDIAL

LATERAL

FIGURE 12.5. Diagram of the sampling technique from the margins of an excisional biopsy of an irregular tumor (T). The labeling of the margins should be marked meticulously at the time of excision to ensure accurate results from the frozen section. If the margins are not accurately labeled, the entire exercise is useless and may be misleading if tumor-containing margins are left behind.

FIGURE 12.6. Orientation and labeling of the samples (M1, L2, etc.) for frozen section to monitor the margins of excision of an eyelid tumor (T). Note that the excision margin of the sample is positioned face down on a piece of cardboard. M: medial; L: lateral.

LATERAL

FIGURE 12.5. Diagram of the sampling technique from the margins of an excisional biopsy of an irregular tumor (T). The labeling of the margins should be marked meticulously at the time of excision to ensure accurate results from the frozen section. If the margins are not accurately labeled, the entire exercise is useless and may be misleading if tumor-containing margins are left behind.

FIGURE 12.6. Orientation and labeling of the samples (M1, L2, etc.) for frozen section to monitor the margins of excision of an eyelid tumor (T). Note that the excision margin of the sample is positioned face down on a piece of cardboard. M: medial; L: lateral.

men accurately and let the pathologist obtain samples from the margins in the laboratory for frozen section purposes (see Figure 12.5). A more surgeon-friendly approach is to obtain the tumor bulk for permanent section processing and then sample and label the excision margins (e.g., M1, M2, etc. for the medial eyelid margins of an eyelid tumor; L1 and L2, etc. for the lateral margins) (Figure 12.6). In this approach, the pathologist should be oriented to the cut surface of the specimen and needs to know whether the cut surface of the specimen is placed up or down on the piece of cardboard.

The advantage of the conventional approach is that the pathologist has full control of the specimen and the deeper margins can be sampled easily. The advantage of the latter approach is that the surgeon will be better oriented to the margins with a list to hand and a simple diagram on the drapes. Such information is very useful, particularly if repeated margins turn out to be positive, since the surgeon knows exactly at what point the margin becomes negative (Figure 12.7). This method, which is the premise of Mohs micrographic surgery, can also be effectively utilized in conventional frozen section sampling.

To obtain the most accurate results from the frozen section, the labeling of the margins should be done meticulously at the time of excision. The labeling should be short and simple and clearly understandable

FIGURE 12.7. Diagram of the labeling technique for multiple frozen sections obtained from different levels of the tumor (T) excision; this is the main principle behind the Mohs microsurgical technique.

to the pathologist. Tissue removed for frozen section should be handled delicately to avoid crush artifacts at the time of excision and transportation. Most of the samples in ophthalmic surgery consist of small pieces of tissue. Even the slightest handling can result in crush artifacts, which in turn may produce misleading results. A point commonly overlooked by the surgeon who is unfamiliar with the frozen section procedure is that the margins of tissue remaining around an area of tumor involvement should not be cauterized until the tissue or frozen section submitted earlier has been proven to be free of tumor. This is because cautery artifacts would make it difficult to interpret the adjacent layer of tissue from questionable margin. Maintaining marginal integrity is particularly important with the deep margins of the excision, which usually involve the subcutaneous adipose tissue.

Frozen section diagnosis in ophthalmology is most commonly utilized in eyelid and conjunctival tumors rather than orbital lesions. For most of the localized presentations of basal and squamous cell carcinomas of the eyelids, the conventional sectioning of the skin ellipse (Figure 12.1) or the pentagonal eyelid excision (Figure 12.6) would reveal satisfactory information about surgical excision margins. If the margins are free, the primary closure takes place. If, on the other hand, one or all margins are found to be involved with the tumor, additional full-thickness frozen sections from the area of concern are submitted for further study. If the deep surgical margin happens to be involved with the tumor, additional specimens are obtained from the base. At this point it is helpful to map the base of the excision and code the deeper layers of tissues with numbers and/or letters (Figure 12.7). Thus the areas of residual tumor are marked on the diagram, and only those areas will be excised. Mapping identifies the exact location of residual tumor, and therefore unin-

volved tissue can be spared; surgical excision is continued until the margins are histopathologically proven to be tumor free. This histographic frozen section technique is the basis of Mohs micrographic surgery.35,36

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