Skin biopsies are essential in dermatology to aid in the correct diagnosis of various conditions and to aid with therapeutic planning. Various skin biopsy techniques exist, including shave, saucerization, curettage, snip, incisional and excisional biopsy. An excisional biopsy is defined by the process of completely removing a solitary skin lesion and will further be discussed in this text.  Excisional biopsies are helpful in evaluating cutaneous tumors, inflammatory processes, and dermal lesions. Complications from excisional biopsies are uncommon and can be minimized by thorough perioperative evaluation and proper technique. While excisional biopsies allow for histopathologic evaluation of various disease processes, clinicopathologic correlation is essential to making the final diagnosis.
Proper perioperative planning is critical to avoid perioperative complications and to achieve a cosmetically optimal result. Important cutaneous landmarks, cosmetic units, and relaxed skin tension lines should be evaluated to best camouflage the resultant scar from the procedure. Asking the patient to perform tasks that alter the skin tension in the area planned for surgery can help identify skin tension lines, i.e., asking a patient to move a limb through its range of motion for a lesion close to a joint or to smile for a lesion on the cheek. 
Excisional biopsies are helpful in the evaluation of lesions for which architectural features aid in the correct histopathologic diagnosis, inflammatory lesions, and deep dermal or subcutaneous lesion. Excisional biopsy is also the best choice for evaluating for a suspected melanoma as the depth of the lesion provides important diagnostic and prognostic information.
The choice of biopsy site depends on the location of the lesion of interest, however, in widespread disease, it is wise to avoid problematic areas that may yield unremarkable histopathologic results or may result in a cosmetically unfavorable outcome. For example, surgical sites below the knee have a higher risk of infection or poor healing, and sites on the back tend to stretch. Other unfavorable sites include the central face and ventral forearm.  Excisional biopsies are generally reserved for lesions on the trunk and limbs. However, Mohs micrographic surgery expands the potential for the use of excisional biopsies in dermatology. 
Necessary equipment for preparation includes:
Excisional biopsies can be performed alone or with a surgical assistant to help keep the surgical field clean and to cut sutures.
Surgical mapping for an excisional biopsy involves identifying the lesion of interest and marking the area around the lesion with a surgical marker, including an appropriate margin around the lesion to ensure complete removal. Two small triangles are then drawn on either side of the lesion in the predetermined orientation of the surgical excision as described above. The resultant shape is an ellipse with an ideal length-to-width ratio of 3:1. This design is intended to reduce or eliminate redundant tissue at either end of the excision, preventing dog-formation upon closure of the surgical site. The resultant scar should be long, thin, and linear that follows the natural contours of the skin.
Local anesthesia is the most common form of anesthesia in cutaneous biopsies. Injection of local anesthesia is often a source of great anxiety for the patient and should be handled gently. 1-2% lidocaine with or without epinephrine is commonly used in dermatologic surgery. The addition of epinephrine aids in decreasing bleeding, prolong anesthetic effects and reduce anesthetic toxicity. Additionally, buffering the anesthetic with sodium bicarbonate helps to decrease the pain associated with the infiltration of the acidic solution. Using a small needle gauge, gently pinching the area to be injected, and avoiding multiple needle sticks through the epidermis also reduce patient discomfort. Local infiltration is achieved by injecting slowly intradermally or subcutaneously. While the onset of action of local anesthetics is almost immediate, full vasoconstriction provided by the addition of epinephrine requires up to fifteen minutes.
After administering anesthesia, the patient is placed in a comfortable position with good surgical lighting and at the appropriate height for the surgeon. The surgical site should is then prepped with antiseptic and draped. Popular agents used in antiseptic preparation include povidone-iodine and chlorhexidine. Special care should be taken in hair-bearing areas by clipping hairs in the surgical field or securing hair with sterile clips, rubber bands, or tape.
The surgeon should thoroughly wash and dry his or her hands before the procedure. A formal surgical hand scrub is unnecessary as prudent and simple hand antisepsis is sufficient. Face masks can be worn as personal protective equipment but are unnecessary in dermatologic surgery. Surgical gloves should be worn and kept clean throughout the duration of the procedure. The need for sterile gloves in dermatologic surgery remains a topic of interest, but recent literature reports no significant difference in surgical site infections when comparing sterile gloves with clean surgical gloves.
Start the incision with the point of the blade contacting the apex of the ellipse. Then, use the sharper belly of the blade to carry the cut along the arc in a smooth and directed fashion while simultaneously maintaining traction of the surrounding area with the non-dominant hand. Repeat the same process on the other side of the lesion. Mark the tissue with non-dissolvable suture or by nicking a specified location of the excision while in situ or after completely removing the tissue. Use toothed forceps to grasp and elevate the tissue at the apex while dissecting the tissue at the level of the subcutis with a scalpel or blunt-tipped scissors. Care should be taken to dissect the tissue along an even plane, yielding a defect with an even base and smooth walls.
Hemostasis can be achieved with direct pressure or by cautery. While heat cautery will work in a wet field, electric cautery will only work in a dry field. Blotting with gauze or cotton-tipped applicator helps to maintain a dry field for electric cautery. Larger vessels may require ligation with absorbable suture. Careful undermining with sharp of blunt techniques may assist in approximating wound edges or to minimize tension on the wound. It is imperative to be mindful of the surrounding anatomy to prevent adverse outcomes.
A layered closure consists of absorbable deep sutures and non-absorbable superficial suture. Deep sutures eliminate dead space, decrease tension on the wound edges of the dermis and epidermis, and facilitate wound edge eversion. If there is little tension on the wound, place the first deep suture in the center of the lesion and the remaining deep sutures halfway between the middle suture and the apices of the lesion. The distance between deep sutures is then progressively halved. If there is tension on the wound, place the deep sutures at the apices of the lesion and then incrementally closer to the center of the lesion. This method helps reduce the amount of tension as the deep sutures are progressively placed. The buried sutures commonly used are the buried vertical mattress suture and the buried horizontal mattress suture.
The superficial sutures are then placed to approximate the epidermal wound edges. This is done with non-absorbable sutures that require removal after the wound is given time to heal, usually between one and two weeks. If the wound is not under tension and there is good epidermal approximation, adhesive tapes or tissue adhesive may be used in place of superficial sutures.
Complications may include
Intraoperative hemostasis and postoperative pressure dressings and ice decrease the likelihood of excessive postoperative bleeding or hematoma formation. Surgical site infection is mostly dependent on wound care by the patient with daily cleaning and bandage changes. Prophylactic antibiotics are indicated if the patient is considered high risk.
Skin biopsies aid in the correct diagnosis of various conditions and aid with therapeutic planning. Excisional biopsies are helpful in the evaluation of cutaneous tumors, inflammatory processes, and dermal lesions.
It is important to discuss expected outcomes after excisional biopsies with the patient. Educate the patient about the expectant scar, wound care instructions, potential complications with healing, and provide information for how the patient should seek help should complications arise. Inform the patient on how long to expect to wait before receiving the biopsy result and arrange proper follow up for the patient depending on the biopsy findings.