Anatomic Considerations

The scalp is a unique adaptation of the epithelial covering of the body. Anatomical variations present in the scalp modify both tumor behavior and the treatment of tumors in this area. The hair-bearing area of the scalp consists of a thick padding of hair follicles, sweat glands, fat fibrous tissue and lymphatics that are interspersed with numerous arteries and veins (Figure 4-1). This thick padding is supported by a tough aponeurotic layer that is fused in the anterior region with the frontalis muscle, and in the posterior region with the occipital muscle. This inelastic layer rests loosely on the periosteum of the

Figure 4-1. The anatomical layers of the scalp.

skull creating a potential subaponeurotic space. Laterally, the temporalis muscle provides an additional barrier between the galea and the periosteum.

Three principal arteries provide a rich blood supply to each side of the scalp. Two of these, the superficial temporal and occipital, are branches of the external carotid artery, while the supraorbital artery is a branch of the internal carotid artery. The lymphatic network of the scalp is also unique in that the scalp has no lymph barriers and contains many medium-caliber channels both subdermally and sub-cutaneously. The lymphatics drain toward the parotid gland, the preauricular area, the upper neck, and the occipital region.

In contrast to the scalp, facial skin is also unique in that it has several distinguishing characteristics on various parts of the face with unique anatomic features providing different functions. For example, the skin around the eyelids is extremely thin with almost no subcutaneous fat. In contrast, the skin around the central part of the face adjacent to the nose and lips is intimately attached to the underlying facial mus cles and offers facial expression. Thus, the skin of the central part of the face is mobile, while there are areas of facial skin along the lateral aspect of the nose, the bridge of the nose, and along the preauric-ular region and temple which are relatively immobile. These unique characteristics of the facial skin have significant surgical implications. Similar to the scalp, the facial skin has a rich blood supply through the facial and superficial temporal arteries. However, unlike the scalp, the facial skin has predictable patterns of lymphatic drainage to preauricular and peri-parotid lymph nodes as well as perivascular facial lymph nodes adjacent to the body of the mandible, eventually draining into the deep jugular chain of lymph nodes.

The most common malignant lesions of the skin of the face and scalp are basal cell carcinomas, squa-mous cell carcinomas, and melanomas. Occasionally one may see rare lesions such as a keratoacanthoma, Merkel cell tumor, and sweat gland carcinoma. If the extent of the excision is such that a primary closure through an elliptical defect is not possible, then one

Figure 4-2. The extent of surgical procedure that would be required for tumors of the scalp depends on the extent and depth of invasion of the tumor.

must consider the applicability of split-thickness or full-thickness skin graft or local, regional or composite microvascular free flaps.

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