Reconstructive Surgery for Skin Cancer

Introduction

The goal of reconstructive surgery for skin cancer is to restore form and function following extirpation of the neoplasm. The partition of oncologic ablation and plastic surgery reconstruction facilitates resection of a cancer lesion independent of the steps required for restoration. Reconstructive strategies balance the characteristics of the resulting wound defect, including both the dimensions of the defect and its inherent functional properties.

Careful analysis of the surgical defect reveals the types of soft and bony tissue that are required to appropriately reconstruct the tissue defect. This analysis allows the reconstructive surgeon to formulate a logical plan that emphasizes conservative measures, such as primary closure and the use of local flaps and skin grafts. As the complexity of the defects increase, including a paucity of local structures or a wound bed with previous radiation or surgery, more complex soft tissue reconstructions such as pedicle flaps or microvascular free tissue transfer become necessary. In general, successful reconstructive surgery restores form and function with minimal donor site deformity, which enhances the patient's quality of life.

Planning reconstructive surgery for skin cancer

The surgical margins for skin malignancies are chosen based on the risk of locoregional recurrence and the etiology of the malignancy. The role of the ablative surgeon is to determine an appropriate diagnosis and attain negative surgical margins. Once negative margins have been determined by frozen section analysis or, depending on the tumor type, by final pathological analysis, the reconstructive surgeon repairs the wound defect. It is therefore critical that both the extirpation and reconstruction are performed in a timely manner that does not interfere with the ultimate goal of obtaining negative pathological margins. A soft tissue flap placed prior to achieving final pathological margins can result in a negative outcome in the management of the skin malignancy, possibly resulting in the removal of the reconstruction. In cases of cutaneous melanoma where the pathological margins are not necessarily determined at the time of surgery, a delayed reconstruction is favored. In contrast, for basal cell or squamous cell carcinoma, margins of 0.5 or 1.0cm, respectively, are accepted pathological measures of negative margins.

In addition, skin grafts, local flaps, or free flaps used for the reconstruction of skin malignancies can potentially interfere with lymphatic mapping. Thus, it is advantageous to perform reconstruction following lymphatic mapping versus before.

For lesions that are too large to be excised completely without immediate reconstruction, it is important to coordinate the reconstructive process with the surgical oncologist, dermatologic surgeon, or general surgeon and determine which donor sites are available to complete the reconstruction. Temporizing a partially excised wound with a biological dressing is a consideration prior to final reconstruction. It is critical to coordinate both the extirpation and the wound reconstruction taking into consideration the oncologic status of the patient.

Immediate and reliable soft tissue coverage is the primary goal of reconstruction following the excision of a skin malignancy. When reconstruction is performed immediately following extirpation, tissue planes are readily available and the soft tissue wound bed is preserved with little to no fibrotic tissue. When the reconstruction is delayed, scar tissue, fibrosis, and wound contracture can inhibit optimal reconstruction. If immediate reconstruction is not possible, the wound bed must be prepared for the eventual reconstruction with appropriate dressings, and debridement may be necessary either prior to or at the time of reconstruction.

The timing of the reconstruction is dictated by the status of the tumor and the surgical pathological margins. For example, basal cell carcinoma can potentially be reconstructed immediately if frozen tissue sections show negative margins. However, for more aggressive types of basal cell carcinoma such as morpheaform, the reconstruction must be delayed until the tumor margins are clearly determined by thorough pathological review or with Mohs surgery. In addition, reconstruction must be delayed in cases of melanoma or other aggressive skin malignancies, such as Merkel cell carcinoma, when the surgeon performing the ablative resection is concerned about the margins and when the margins are not established immediately because of the need for specific immunological stains of the tissue samples. Such is often the case with advanced primary desmoplastic melanoma or large lentigo maligna melanoma of the head and neck region.

However, if certain mitigating factors are evident, such as advanced age, multiple comorbidities, or the need for locoregional control with adjuvant radiotherapy, then a one-stage procedure may be warranted. If a one-stage procedure cannot be accomplished, the wound is temporized, and the final status of the pathological margins is determined. Delayed wound reconstruction, although not optimal, is at times unavoidable and required. In the case of delayed reconstruction, there is typically a greater soft tissue deficit requiring reconstruction. However, with proper wound care and planning, delayed reconstruction of soft tissue defects secondary to skin malignancy resection can be performed appropriately and with optimal success.

Surgical wounds are assessed by measuring their physical dimensions and on the basis of their location. In many instances, the wound is adjacent to critical structures, such as ocular, oral, and nasal structures. Aesthetic as well as functional parameters must also be considered. In addition, previous incisions must be taken into consideration when assessing the wound, as they may interfere with the planned reconstruction. A clinical and radiographic examination of the structural components involved is required to plan a successful reconstruction. Loss of skin, subcutaneous tissue, fascia, muscle, nerves, bone, and, often, mucosa must also be accounted for. For example, a large skin malignancy of the lip can involve structures outside and inside the oral cavity ( Fig. 51.1 ), which would require reconstruction of all the components of the cheek, including both extraoral and intraoral components.

Selection of reconstructive techniques

The selection of appropriate reconstructive techniques is critical. The physiological status of the patient must be considered and balanced with the overall reconstructive plan. A patient unable to tolerate lengthy surgery owing to multiple comorbidities must be considered for a more conservative type of reconstruction rather than a lengthier procedure involving protracted general anesthesia or the potential for multiple surgeries.

The deleterious effects of radiation therapy on wound healing must be considered in any reconstruction of an acquired cancer defect. Prior radiation therapy can preclude the use of local tissue transfer for the reconstruction of a wound bed owing to its negative effects on the inherent vascularity of the local tissue. Free tissue transfer of composite soft tissue constructs can potentiate wound healing in a previously irradiated bed by recruiting normal, robust vascularized tissue. In addition, if a reconstructed wound requires adjuvant radiation therapy, the vascularized tissue will help with the durability of wound healing.

Reconstruction of any skin defect is performed by primary closure, skin graft, local flaps, or microvascular free tissue transfer. The core principle of this reconstructive algorithm is to progress from simple to more complex reconstructions on the basis of the specific wound requirements. The primary goal of any surgeon should be to close a wound primarily with local tissue under physiologic tension. When primary closure is not feasible, skin grafts or local flaps of tissue can be used.

Local flaps allow the defect to be reconstructed with like tissue. These flaps typically are based on a random subdermal plexus for their blood supply. Local flaps can also be based on named blood vessels and be raised as fasciocutaneous, myocutaneous, or adipofascial flaps. These are specifically described as axial pattern flaps. Free microvascular tissue transfers can also be used, requiring the use of tissue constructs based on named vessels that are raised separately in a different part of the body and transplanted to the recipient vessels at the site of the defect. Complex reconstructive surgeries are favored over local flaps when the local tissue is unavailable, the wound bed is fibrotic or irradiated, or the patient's defect requires well-vascularized tissue over critical neurovascular or bony structures.

Local flaps

Local flaps allow surgeons to reconstruct soft tissue defects with similar tissue from an adjacent location. These random flaps represent skin and subcutaneous tissue based on a subdermal plexus vascular supply. By definition, random flaps do not have a distinct named blood supply, in contrast to axial flaps, which are based on named blood vessels (e.g. pectoralis flap or anterolateral thigh flap; Fig. 51.2 ). Local random flaps can be raised using various methods, including rotation-advancement, transposition, z-plasties and rhomboid flaps ( Fig. 51.3 ). An axial pattern flap, with its named blood supply, is elevated with an arterial and venous pedicle. These flaps can be fasciocutaneous, myocutaneous, or osteocutaneous, which allows the surgeon to reconstruct a skin cancer defect using like tissue with its own intrinsic blood supply and possibly using other tissue components to obliterate dead space, contour the wound, and cover critical neurovascular structures.