Surgical management of primary cutaneous melanoma or melanoma at other unusual sites

INTRODUCTION — Melanomas most frequently occur in sun-exposed areas of the skin (ie, cutaneous melanoma of the trunk, extremities, head, and neck) but may arise in number of other sites such as the nail bed, palms, or soles (eg, acral lentiginous melanoma), on the external genitalia, in mucous membranes (mucosal melanoma), or in the eye (uveal or conjunctival melanoma).

The surgical principles for managing primary cutaneous melanoma presenting in the head, neck, trunk, and extremities are reviewed. The management of more unusual sites, including mucosal and uveal, are briefly discussed and reviewed more fully in separate topic reviews. (See "Locoregional mucosal melanoma: Epidemiology, clinical diagnosis, and treatment" and "Initial management of uveal and conjunctival melanomas".)

ROLE OF SURGERY — Proper surgical management is critical for the diagnosis, staging, and optimal treatment of primary cutaneous melanoma.

The goals of surgery include:

●Histologic confirmation of the diagnosis, which ideally had been established prior to definitive surgical management through an appropriately planned biopsy. (See "Melanoma: Clinical features and diagnosis", section on 'Diagnosis confirmation' and "Pathologic characteristics of melanoma".)

●Obtaining complete and accurate pathologic staging of the primary tumor (and when appropriate, regional nodal basin staging by sentinel lymph node biopsy [SLNB]) to guide further treatment and management at the same operative setting as wide excision of the primary melanoma. (See "Tumor, node, metastasis (TNM) staging system and other prognostic factors in cutaneous melanoma".)

●Wide excision of the primary melanoma site with an appropriate margin of normal tissue around the primary site to minimize the risk of local recurrence. (See 'Resection margins' below.)

●Wide excision of the primary site with optimal functional and cosmetic outcomes.

Surgery is also an important component in the management of other aspects of melanoma staging and treatment. These issues, including regional nodal basin staging by SLNB at the same operative setting as wide excision of the primary melanoma, are the subject of other topic reviews.

●Regional lymph nodes (see "Evaluation and management of regional nodes in primary cutaneous melanoma")

●Local recurrences (see "Cutaneous melanoma: Management of local recurrence")

●In-transit metastases (see "Cutaneous melanoma: In-transit metastases")

●Distant metastatic disease (see "Metastatic melanoma: Surgical management")

MELANOMA OF THE TRUNK OR EXTREMITIES

Wide excision — The initial diagnosis of cutaneous melanoma should be made by biopsy. The approach to biopsy of the suspicious lesion is reviewed elsewhere. (See "Melanoma: Clinical features and diagnosis", section on 'Biopsy'.)

Based on the biopsy result, primary cutaneous melanomas are clinically staged according to their pathologic features (Breslow thickness, presence or absence of ulceration) and whether there is clinical evidence on preoperative physical examination and imaging of regional nodal basin involvement; satellite or in-transit metastases; or distant metastases (table 1 and table 2). (See "Melanoma: Clinical features and diagnosis" and "Tumor, node, metastasis (TNM) staging system and other prognostic factors in cutaneous melanoma".)

The thickness of the melanoma is a key factor in determining the clinical stage of the lesion and the recommended margin of normal tissue when resecting the primary tumor. (See 'Resection margins' below and "Pathologic characteristics of melanoma".)

Most wide excisions are performed using an elliptical incision, with the required margin measured in the short axis of the ellipse. The use of an elliptical incision facilitates a generally linear closure along the lines of natural tension, while minimizing standing cones ("dog ears") that may be cosmetically unpleasing. Closure may sometimes be facilitated by curving the ends of the ellipse in a sigmoidal or "hurricane-style" fashion. The specimen should be oriented for the pathologist. It is important to note that the data supporting various margin widths are based on studies in which the surgical margin was measured by the surgeon at the time of resection around the biopsy site and/or residual intact component in situ (ie, a surgical margin) rather than by the pathologist after wide excision has been performed (ie, histologic margin). Due to the elasticity of the skin, compared with the dimensions marked by the surgeon, the skin specimen will almost always shrink in size (hence gross pathologic measurements are often less than measured surgical dimensions); the wide excision field defect will generally expand once the specimen has been removed. (See 'Resection margins' below.)

Wide excision is generally performed down to, but not including, the muscle fascia. Routine inclusion of the muscle fascia during wide excision of cutaneous melanomas of the extremities or trunk does not appear to offer any benefit in terms of long-term local disease control and is not recommended except in uncommon scenarios when it might be necessary to clear a deep margin for an extensive primary melanoma, and/or the fascia was previously disrupted during the initial biopsy procedure. A retrospective review of 964 cases of melanoma ≥1 mm thick included 278 patients (29 percent) who underwent resection of the muscle fascia [1]. There was no decrease in the rate of local recurrence when the muscle fascia was resected. Resection of the fascia was associated with an increase in the incidence of in-transit and regional lymph node metastases. Whether this reflects an effect on the barrier to lymphatic spread or patient selection bias is unknown.

Resection margins — The recommended width of radial resection margin of normal tissue around a primary cutaneous melanoma lesion is extrapolated from, and based upon, several large clinical trials that examined the impact of the surgical margin on local recurrence rates (table 3 and table 4) [2-11]. The depth of resection margin was not formally explored in these clinical trials, nor did patients enrolled undergo sentinel lymph node biopsy (SLNB), as it was not standard of care at the time these trials were conducted. Of note, these clinical trials were also conducted prior to the era of systemic and adjuvant immunotherapy and targeted therapy, which can have major impacts on overall and relapse-free survival.

It is also worth noting that the optimal extent of wide excision for primary cutaneous melanoma remains a subject of investigation, with at least one clinical trial underway. This trial randomizes patients with primary cutaneous melanoma >1 mm Breslow thickness to wide excision with either a 1 cm excision margin or a 2 cm excision margin [12,13]. Outcome measures of this study are local recurrence and melanoma-specific survival. In select cases, reconstruction of the surgical site may be delayed pending "rush" permanent histopathology, since frozen section intraoperative assessment is not generally indicated for margin assessment of primary melanocytic lesions [14].

Melanoma in situ: 0.5 to 1 cm margin — For patients with melanoma in situ (Tis), there are no data from randomized trials to define the optimal extent of surgical resection. We agree with guidelines from the National Comprehensive Cancer Network (NCCN) and the American Academy of Dermatology (AAD) that recommend a margin of 0.5 to 1 cm [3,11,15,16]. We most commonly use a 0.5 cm margin for melanoma in situ followed by evaluation of the histopathology to ensure clearance.

If the margin is inadequate, additional excision can be performed; however, this is not required for the most of these lesions. Surgeons may sometimes select a 1 cm margin rather than 0.5 cm for melanoma in situ for large and/or ill-defined lesions in which it is difficult to discern the gross extent of the lesion or when there is concern for possible occult invasive melanoma.

T1 melanoma: 1 cm margin — For melanomas ≤1 mm thick (T1), we agree with the NCCN and AAD guidelines that recommend a surgical excision margin of 1 cm [3,11]. The original data supporting this approach are from several large trials that showed a low recurrence rate for a 1 cm margin in patients with T1 melanoma [4-6,17,18]:

●In a World Health Organization (WHO) trial, 612 patients with melanomas <2 mm thick were randomly assigned to wide excision with a 3 cm margin or with a 1 cm margin [4,17,18]. At 12-year follow-up, survival rates were similar (87 versus 85 percent). The local recurrence rate was 1.8 percent overall and similar between the groups. The four local recurrences that occurred were in patients with primary melanoma >1 mm thick in the 1 cm margin group; there were none in the 3 cm margin group. Based upon these results, a 1 cm margin was recommended for patients with melanoma ≤1 mm thick, but no recommendation was made for thicker melanomas. However, in a subsequent report with additional follow-up, the 3 cm margin group had a local recurrence rate of 1 percent [4].

●In a trial conducted by the Swedish Melanoma Study Group, 989 patients with melanomas 0.8 to 2 mm thick were randomly assigned to 2 or 5 cm resection margins [5]. At a median follow-up of 11 years, the rate of local recurrence for all patients was less than 1 percent and was similar in both groups. There were no differences between the groups in overall or disease-free survival.

●A third trial sponsored by the French Cooperative Group consisted of 362 patients with melanomas ≤2 mm in thickness who were randomly assigned to 2 versus 5 cm margins [6]. There was no difference between the groups in the risk of local recurrence or in overall survival.

Local recurrence following resection of T1 melanoma is overall low; in a case-control study, it occurred at a median time of 37 months and was associated with narrower excision margins (<8 mm histologic excision margin corresponding to <1 cm surgical margin), as well as other histologic features (desmoplastic, acral, lentigo maligna melanoma subtypes, melanomas composed predominantly of spindle cells) [15,19].

T2 melanoma: 1 to 2 cm margin — For melanomas >1 to 2 mm thick (T2), we agree with the NCCN and AAD guidelines that recommend a 1 to 2 cm margin, depending on anatomic constraints based upon the location of the primary melanoma [3,20].

In the studies described above (see 'T1 melanoma: 1 cm margin' above), outcomes were similar for 2 versus 5 cm margins, and 1 cm margin was similar to 3 cm margin [4-6,17,18]. In the original WHO study, the wider margin (3 cm) for 1 to 2 mm lesions was associated with zero local recurrence, a rate lower (but not significantly lower) than the narrower 1 cm margin. At later follow-up, local recurrence was low in both arms (not zero), but not significantly different between the groups, suggesting that the narrower 1 cm margin is adequate. Thus, when anatomically constrained, a margin of at least 1 cm can be used.

T3/T4 melanoma: 2 cm margin — For melanomas >2 mm thick, we agree with the NCCN and AAD guidelines that recommend a 2 cm margin. Clinical trials have not demonstrated any benefit for excision margins >2 cm. Clinical trial data supporting this approach include the following:

●In a multicenter European trial (53 sites in Denmark, Sweden, Norway, and Estonia) that enrolled patients from 1992 to 2004, 936 patients with a melanoma on the trunk or extremity greater than 2 mm thick were randomly assigned to either a 2 or 4 cm resection margin [7]. Data regarding use of systemic therapy were not provided, allowing an analysis of the effect of surgery alone (routine use of effective therapy for stage III disease was not practiced at the time of this study). The study may have been underpowered due to slow accrual. Melanoma-specific survival with longer-term follow-up was similar comparing the 2 and 4 cm margin groups (median 19.6 years; hazard ratio [HR] 0.98, 95% CI 0.83-1.14) [8]. There were also no statistically significant differences in overall survival or recurrence-free survival (median follow-up 6.7 years). On multivariate analysis, the highest risk of death was associated with a combination of male sex, age >60 years, thickness >3 mm, location on the trunk, and ulcerated melanoma. Adjustment for prognostic factors did not show any significant effect for width of the resection margin. Local recurrence and recurrence-free survival were not assessed in the longer term. The 19.6-year follow-up was remarkable and notable since only two patients were lost to follow-up at 5.7 and 8.7 years. The study included 53 hospitals from four countries, supporting generalizability of the results. Also remarkable was that all patients were treated per protocol. These long-term data confirmed the short-term mortality results of this trial, as well as data from other mid- to long-term data sets.

●The Melanoma Intergroup Trial randomly assigned 468 patients with intermediate thickness (1 to 4 mm) melanomas to 2 or 4 cm excision margins [9,21,22]. At a median follow-up of eight years, overall survival and local recurrence-free survival rates were similar for the 2 cm compared with 4 cm excision margin (80 versus 84 percent, respectively, and 0.8 versus 1.7 percent, respectively). On multivariate analysis, independent predictors of local recurrence included tumor thickness and ulceration, but not the excision margin. Patients treated with the 2 cm excision margin had a shorter hospital stay and required skin grafting less frequently (11 versus 46 percent).

For melanomas thicker than 4 mm, survival and local recurrence outcomes depend upon the presence of regional and/or distant disease.

●In the European trial of 936 patients, 470 patients had melanoma >3 mm (233 in the 2 cm excision margin group and 241 in the 4 cm excision margin group) [8]. Adjustment for prognostic factors including thickness >3 mm did not change the risk of death for the 2 cm excision margin compared with 4 cm excision margin [8].

●In the British trial involving 900 patients, 243 patients (27 percent) had lesions >4 mm thick [10]. Overall, that trial observed an increased risk of local recurrence with 1 cm surgical margins compared with 3 cm (HR 1.26), but with a similar overall survival rate.

●The only other series of data for patients with thick (≥4 mm) primary melanomas comes from a retrospective review of 278 patients with a median tumor thickness of 6 mm [23]. There was no correlation between the width of resection (>2 cm versus <2 cm) and local recurrence or overall survival.

MELANOMA OF OTHER SITES

Head and neck — The skin of the head and neck accounts for 15 to 25 percent of all primary melanomas, even though this region accounts for about 9 percent of the total surface area of the body [24-27]. Multiple factors may contribute to this anatomic predilection, including higher levels of sun exposure and a melanocyte content of the skin that is two- to threefold higher than other regions. The literature is divided regarding the disease specific outcomes of head and neck melanoma compared with other anatomic sites [25,28-32]. (See "Melanoma: Epidemiology and risk factors".)

The recommendations for surgical margins during wide excision of head and neck melanomas are the same as for other cutaneous melanomas (see 'Resection margins' above). However, these recommendations were derived from trials in which most patients had melanomas of the trunk or extremities. In the head and neck, such margins are not always attainable and may result in functional disability. Skin grafts are generally avoided whenever possible on the face, but the appropriate excision margins for the extent of tumor thickness should not be compromised solely because of cosmetic factors [33,34]. Flap reconstruction may be required and can often be accomplished with excellent cosmetic results. (See "Overview of flaps for soft tissue reconstruction".)

It is notable that melanoma in situ lesions on the face, particularly lentigo maligna type, may have indistinct borders and more lateral spread compared with lesions in other locations. For these lesions, Mohs micrographic surgery (MMS) is sometimes used; in selected series, the local recurrence rates and survival have been reported to be similar to wide excision [16,35-39]. However, it is important to note that MMS is not considered the standard of care for invasive melanoma (ie, T1 to T4). (See "Mohs surgery", section on 'Specific indications'.)

Other sites — Although melanomas are most frequent in sun-exposed areas of the skin (ie, cutaneous melanoma of the trunk, extremities, head/neck), melanoma may arise at other sites, such as in the nail bed, palms, or soles (acral/lentiginous melanoma), on the external genitalia, in mucous membranes (mucosal melanomas), or in the eye (uveal melanoma). These melanomas differ in their epidemiology even though they have a shared cellular origin with the more common cutaneous melanomas [40,41]. While cutaneous and ocular melanomas share a common environmental risk factor (ultraviolet radiation), this may not be the case for all mucosal melanomas [42,43].

Early diagnosis facilitates proper treatment and improves survival for patients with these unusual variants. No prospective trials have been undertaken to determine the optimal margins for mucosal, ocular, or acral lentiginous melanomas. The rarity of these melanomas has precluded randomized trials upon which to base treatment decisions, and these rare tumors have generally not been a substantial component of trials designed to determine optimal excision margins. (See 'Resection margins' above.)

Acral melanoma — Acral melanomas, which occur on subungual sites and the palms and soles, are usually lentiginous [44,45]. In one series, 28 percent of these lesions were unpigmented [46]. (See "Melanoma: Clinical features and diagnosis", section on 'Acral lentiginous melanoma'.)

Guidelines for cutaneous melanoma excision margins should be followed and preservation of function maximized when possible and oncologically appropriate. (See 'Resection margins' above.).

From an oncologic perspective, it is not generally necessary to resect bone. However, because wide excision of subungual or distal digit invasive melanoma usually yields insufficient soft tissue to maintain a functional digit, partial phalanx bony resection is commonly required. Phalanx-preserving approaches may sometimes be used for subungual or distal digital melanoma in situ. In this clinical scenario, skin grafts or other reconstructive options can be used. For proximal digit and/or web-space-based invasive melanomas, wide excision with preservation of underlying tendonous and bony structure can often be achieved followed by reconstruction of the wide excision site with a skin graft, in contrast to the common need for partial amputation to accompany the wide excision for distal digit invasive melanoma.

In some series, patients with acral melanomas have a worse prognosis compared with patients who have cutaneous melanomas of the extremities of the same tumor, node, and metastasis (TNM) stage, possibly due to a more aggressive biological course [47-51]. In a multivariate analysis of a single-institution series that included 281 patients with acral melanoma and 843 matched controls, ulceration of the primary tumor and a positive sentinel lymph node biopsy were independently associated with a significantly shorter disease-specific survival. (See "Pathologic characteristics of melanoma" and "Tumor, node, metastasis (TNM) staging system and other prognostic factors in cutaneous melanoma".)

Subungual — Subungual melanoma arises from the nail matrix and accounts for 0.7 to 3.5 percent of all cases of melanomas [52-54]. The presentation and diagnostic approach to patients with subungual melanoma are discussed separately (see "Overview of nail disorders", section on 'Melanoma').

Guidelines for cutaneous melanoma excision margins should be followed and preservation of function maximized when possible and oncologically appropriate. (See 'Resection margins' above.)

●Subungual melanomas involving the toes can generally be managed with digital amputation at the interphalangeal or metatarsal-phalangeal joint depending on location and local extent of disease, although phalanx-preserving approaches may sometimes be used for subungual melanoma in situ.

Postoperative consultation to fit appropriate shoes/orthotics is appropriate. (See "Techniques for lower extremity amputation", section on 'Foot amputations'.)

●Whenever possible, subungual melanomas of the fingers should be resected at the distal interphalangeal joint to preserve function [55]. Proximally located cutaneous melanomas on the fingers can often be managed with excision (as with other cutaneous melanomas) and without bony resection; in such situations, reconstruction can often be achieved by skin graft or possibly a local flap for soft tissue coverage. (See "Upper extremity amputation", section on 'Digit and thumb amputation' and "Surgical reconstruction of the upper extremity".)

As with other melanomas, increasing tumor thickness and the presence of ulceration in the tumor are associated with a worse prognosis [56]. (See "Tumor, node, metastasis (TNM) staging system and other prognostic factors in cutaneous melanoma".)

Plantar/palmar — For melanomas arising on the sole of the foot or the palm of the hand, excisions are almost never closed, primarily due to the lack of surplus skin. Skin grafts can be performed, but some weight-bearing areas may require more substantial soft tissue coverage. One approach is to allow the excision wound to granulate before skin grafting, either through dressing changes or with negative pressure wound therapy. Alternatively, rotation, advancement, or free flaps may be used. (See "Negative pressure wound therapy" and "Overview of flaps for soft tissue reconstruction" and "Surgical reconstruction of the upper extremity" and "Surgical reconstruction of the lower extremity".)

The prognosis for patients with plantar melanoma is worse compared with that for patients with melanomas of the lower extremity of comparable thickness [49-51]. This was illustrated in a series of 51 patients with plantar melanoma and 239 controls with stage I melanomas of the leg [57]. The five-year disease-free survival rates were significantly worse for patients with plantar melanomas compared with those with primary leg lesions (82 versus 95 percent for lesions <1.5 mm, 51 versus 71 percent for lesions 1.5 to 3.49 mm, and 46 versus 0 percent for lesions ≥3.5 mm thick). At the author's institution, findings were similar among patients diagnosed and treated for T1 melanoma between 1994 to 2009 [49]. Disease-specific survival was worse among 129 patients with T1 acral lentiginous melanoma compared with 699 patients with T1 non-acral lentiginous melanoma (five-year survival: 90 versus 99 percent, respectively; ten-year survival: 82 versus 98 percent, respectively).

Unusual sites

●Genital melanoma – Melanoma presenting on the male or female external genitalia is rare and associated with a poor prognosis. These may require gynecologic, urologic, and/or plastic/reconstructive expertise to achieve optimal resection margins while sparing/reconstructing the genitalia, whenever possible. (See "Carcinoma of the penis: Epidemiology, risk factors, and pathology", section on 'Melanoma' and "Vulvar cancer: Epidemiology, diagnosis, histopathology, and treatment", section on 'Melanoma'.)

●Mucosal melanoma – Mucosal melanomas can occur at a variety of sites, including the head and neck (oral cavity, nasal cavity, paranasal sinuses), anorectal region, female genital tract, and urinary tract. Approach towards the resection of these varied lesions depends upon their location. The pathogenesis, presentation, and management of mucosal melanoma is discussed separately. (See "Locoregional mucosal melanoma: Epidemiology, clinical diagnosis, and treatment".)

●Uveal melanoma – The unique presentation and surgical management of uveal melanoma is reviewed elsewhere. (See "Initial management of uveal and conjunctival melanomas" and "Metastatic uveal melanoma".)

DESMOPLASTIC MELANOMA — Desmoplastic melanoma is a rare variant that comprises less than 5 percent of melanoma cases [58]. Desmoplastic melanoma is more commonly diagnosed in men with a 2:1 male-to-female ratio. Patients tend to be older at diagnosis (median age 60 to 70 years) compared with patients with non-desmoplastic melanoma (median age approximately 50 years) [58-61]. Pure desmoplastic melanoma is empirically defined by most as >90 percent of the invasive melanoma and associated with prominent stromal fibrosis. Desmoplastic melanoma is more common in the head and neck region than in other areas of the body, with most series reporting 50 percent or more cases in the head and neck location [58,61].

Although desmoplastic melanomas may surround or directly invade nerves (a variant known as neurotropic melanoma), in general, the prognosis associated with desmoplastic melanoma appears to be better compared with other cutaneous melanomas of the same stage [58,62-70]. The pathological features of desmoplastic melanoma and correlation with prognostic factors are reviewed separately. (See "Pathologic characteristics of melanoma".)

The initial management of patients with desmoplastic melanoma is wide excision with margin based on the thickness of the primary tumor (see 'Resection margins' above). Negative margins may sometimes be difficult to obtain but should be sought in all cases; appropriate margin is important for local control, particularly for pure desmoplastic melanoma. Pure desmoplastic melanomas appear to have lower rates of lymph node involvement compared with mixed desmoplastic and non-desmoplastic melanomas (2.2 percent versus 15.8 and 17.5 percent, respectively) [63,71-74]. However, there is variability in reported rate of sentinel lymph node biopsy (SLNB) positivity in desmoplastic melanoma, possibly due to limitations of histopathologic reproducibility or reporting [75,76]. Thus, the role of SLNB for patients with pure desmoplastic melanoma is controversial, unlike for patients with conventional melanoma or mixed desmoplastic melanoma subtypes.

Following wide excision, adjuvant radiotherapy can be considered with multidisciplinary input in the treatment of primary desmoplastic melanoma to improve local control in patients at high risk of local recurrence, such as in cases in which extensive neurotropism is present or if achievable excision margins are suboptimal [71,77-79]. (See "Radiation therapy in the management of melanoma", section on 'Desmoplastic melanoma'.)

ADJUVANT THERAPY AND SURVEILLANCE AFTER SURGERY — Adjuvant therapy and surveillance after initial surgical management of primary cutaneous melanoma are discussed separately. (See "Adjuvant and neoadjuvant therapy for cutaneous melanoma" and "Radiation therapy in the management of melanoma" and "Staging work-up and surveillance of cutaneous melanoma", section on 'Surveillance'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Melanoma screening, prevention, diagnosis, and management" and "Society guideline links: Mohs surgery".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Beyond the Basics topics (see "Patient education: Melanoma treatment; advanced or metastatic melanoma (Beyond the Basics)" and "Patient education: Melanoma treatment; localized melanoma (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Melanoma diagnosis – Biopsy is necessary to establish a diagnosis of melanoma. Once melanoma has been confirmed, wide excision of the primary melanoma site with an appropriate surgical margin of normal tissue based on tumor thickness and anatomic location is necessary for definitive treatment and pathologic staging. When sentinel lymph node biopsy (SLNB) is indicated for surgical staging, wide excision and SLNB should be performed in the same operative setting. (See 'Role of surgery' above and "Evaluation and management of regional nodes in primary cutaneous melanoma".)

●Wide excision – The recommended width of normal tissue to resect (ie, surgical or resection margin) at the time of definitive surgical treatment for primary cutaneous melanoma of the trunk and extremities is based on the thickness of the primary tumor (table 1). Note that these margins do not refer to histological margin from the wide excision pathology report. (See 'Wide excision' above.)

●Margins for cutaneous melanoma – We agree with guidelines from the National Comprehensive Cancer Network (NCCN) and the American Academy of Dermatology (AAD). For most cutaneous melanomas, we suggest the margins for surgical resection given below, rather than narrower or wider margins (Grade 2C) (see 'Resection margins' above):

•For melanoma in situ (Tis) – A 0.5 to 1 cm surgical resection margin; a 0.5 cm margin is commonly used. No randomized trial data are available to support either a narrower or wider resection. Mohs micrographic surgery may also be appropriate for melanoma in situ, particularly for lentigo maligna type located in the head and neck region, in selected patients. (See 'Melanoma in situ: 0.5 to 1 cm margin' above.)

•For cutaneous melanomas ≤1 mm thick (T1) – A 1 cm resection margin. Based on the available clinical trial data, a wider resection does not appear to improve recurrence-free or overall survival. (See 'T2 melanoma: 1 to 2 cm margin' above.)

•For cutaneous melanomas >1 to 2 mm thick (T2) – A 1 to 2 cm resection margin. Based on the available clinical trial data, a wider resection margin has not improved recurrence-free or overall survival. For T2 melanoma in which a 2 cm margin is anatomically constrained or the 2 cm margin would require a skin graft, a 1 cm margin is acceptable. (See 'T2 melanoma: 1 to 2 cm margin' above.)

•For cutaneous melanomas >2 mm thick (T3, T4) – A 2 cm resection margin. Based on the available clinical trial data, a more wider resection margin has improved recurrence-free or overall survival. For T4 melanomas, outcomes depend predominantly upon the presence of regional and/or distant disease. (See 'T3/T4 melanoma: 2 cm margin' above.)

●Other melanoma sites

•Head and neck melanoma – For patients with cutaneous melanoma arising in the skin of the head and neck region, similar principles of wide excision should be applied. Adjuvant radiation therapy may be indicated if the location of the melanoma precludes an adequate resection margin or if the lesion is at particularly high risk of local recurrence (eg, desmoplastic melanoma). (See 'Head and neck' above and 'Desmoplastic melanoma' above and "Adjuvant and neoadjuvant therapy for cutaneous melanoma".)

•Subungual/plantar/palmar sites – For patients with melanomas arising in subungual or plantar/palmar sites or on mucous membranes, similar principles of wide excision should be applied, but these sites may require specific resections depending upon the anatomic location and restraints. Wide resection >1 cm may preclude primary closure, and skin grafts or reconstructive techniques are often required for wound coverage. (See 'Acral melanoma' above.)