Desmoplastic melanoma: a diagnostic trap for the unwary

Randomized Trial of Postoperative Radiation Therapy After Wide Excision of Neurotropic Melanoma of the Head and Neck (RTN2 Trial 01.09)

BACKGROUND

Cutaneous neurotropic melanoma (NM) of the head and neck (H&N) is prone to local relapse, possibly due to difficulties widely excising the tumor. This trial assessed radiation therapy (RT) to the primary site after local excision.

METHODS

Participants from 15 international centers were randomized to observation or RT. The participants were required to have microscopically negative excision margins 5 mm wide or wider and no evidence of disease elsewhere. The primary outcome was time to local relapse. The secondary outcomes included time to any recurrence, overall survival (OS), and toxicity.

RESULTS

The trial ceased prematurely due to slow recruitment and the COVID-19 pandemic. During 2009-2020, 50 participants were randomized: 23 to observation and 27 to RT. The most common NM subsites were scalp (32%), midface (22%), and lip (20%). The median depth of invasion was 5 mm, and desmoplasia observed in 69%. The median duration from randomization to last contact was 4.8 years. Four participants (8%) experienced local relapse as a first recurrence during the study period: 3 in the observation arm and 1 in the RT arm (hazard ratio [HR] 0.29; 95% confidence interval [CI] 0.03-2.76; p = 0.279). No statistically significant difference in time to any relapse or OS was observed. More than 6 months after randomization, grade 3 or greater toxicity was experienced by 10% of the participants in the observation arm and 12.5% of the participants in the RT arm of the study.

CONCLUSION

Due to low accrual, the role of adjuvant RT for cutaneous NM of the H&N excised with microscopically negative margins 5 mm wide or wider remains undefined. Its routine use cannot be recommended. Local relapse might be less common than previously anticipated based on retrospective reports.

Association of Excision Margin Size With Local Recurrence and Survival in Patients With T1a Melanoma at Critical Structures

Importance

Melanoma guidelines recommend surgical excision with 10-mm margins for T1 melanoma. However, this procedure may be problematic at sites close to critical structures such as the scalp, face, external genitalia, acral, periumbilical, and perineal areas.

Objective

To compare outcomes of wide (10-mm margins) vs narrow (5-mm margins) excision in patients with T1a melanoma near critical structures.

Design, Setting, and Participants

This cohort study was a retrospective comparison of 1341 consecutive patients aged 18 years or older from the National Cancer Institute of Milan, Italy, diagnosed between 2001 and 2020 with T1a cutaneous melanoma close to critical structures who accepted wide excision vs narrow excision.

Exposures

Local recurrence and melanoma-specific mortality (MSM) rates with 5-mm vs 10-mm excision margins.

Main Outcomes and Measures

The primary aim of the study was to ascertain whether a narrower (5-mm) vs wider (10-mm) excision margin was associated with local recurrence and MSM. The secondary aim was to compare the need for reconstructive surgery in the groups defined by excision margin width. Between April 28 and August 7, 2022, associations were assessed by weighted Cox and Fine-Gray univariable and multivariable models.

Results

A total of 1179 patients met the inclusion criteria (median [IQR] age, 50.0 [39.5-63.0] years; female, 610 [51.7%]; male, 569 [49.3%]). Six hundred twenty-six patients (53.1%) received a wide excision (434 [69.3%] with linear repair and 192 [30.7%] with flap or graft reconstruction) and 553 (46.9%) received a narrow excision (491 [88.8%] with linear repair and 62 [11.2%] with flap or graft reconstruction). The weighted 10-year MSM was 1.8% (95% CI, 0.8%-4.2%) in the wide group and 4.2% (95% CI, 2.2%-7.9%) in the narrow group; the weighted 10-year local recurrence rate was 5.7% (95% CI, 3.9%-8.3%) in the wide group and 6.7% (95% CI, 4.7%-9.5%) in the narrow group. Breslow thickness greater than 0.4 mm (subdistribution hazard ratio [sHR] for 0.6 vs 0.4 mm, 2.42; 95% CI, 1.59-3.68; P < .001) and mitotic rate greater than 1/mm2 (sHR for a single increment, 3.35; 95% CI, 2.59-4.32; P < .001) were associated with worse MSM. Multivariable analysis showed that acral lentiginous melanoma, lentigo maligna melanoma, and increasing Breslow thickness were associated with a higher incidence of local recurrence.

Conclusions and Relevance

The study's findings suggest that local excision with 5-mm margins for T1a melanoma may not be associated with an increased risk of local recurrence. Breslow thickness greater than 0.4 mm, mitotic rate greater than 1/mm2, and acral lentiginous melanoma and lentigo maligna melanoma subtypes were associated with a higher risk of recurrence. These findings may be useful for future melanoma treatment guidelines.

Representativeness of initial skin biopsies showing pure desmoplastic melanoma: implications for management

Desmoplastic melanoma (DM) is an uncommon subtype of melanoma with distinct clinicopathological features. It is classified into pure desmoplastic melanoma (PDM) when the proportion of desmoplastic melanoma is ≥90% of the dermally-invasive component, and mixed desmoplastic melanoma (MDM) when the proportion of desmoplastic melanoma is <90%. Studies have reported a lower sentinel lymph node biopsy (SLNB)-positivity rate in PDM compared to MDM and non-DM. As a result, some have recommended not performing SLNB in PDM patients. When PDM is identified in a partial biopsy of a melanoma, there is a risk that sampling bias may under-recognise MDM, but to the best of our knowledge this has not been previously assessed or quantified. The aim of this study was to assess the concordance of the proportion of desmoplastic melanoma in an initial partial biopsy of PDM with the proportion in the entire tumour following complete excision, in patients with cutaneous melanoma. A secondary aim was to determine how frequently this potentially resulted in a patient not receiving a SLNB. Seventy-eight cases of cutaneous melanoma were identified from the Melanoma Institute Australia (MIA) database and 23 cases from the Memorial Sloan Kettering Cancer Centre (MSKCC), where an initial biopsy contained PDM and a subsequent wide excision had residual invasive melanoma. Clinicopathological features were analysed in all patients, including whether a SLNB was performed, the results of SLNB, and any subsequent recurrence. Ninety percent (91/101) of cases were still classified as PDM in the complete wide excision specimen while 10% (10/101) of cases were reclassified as MDM, which was a significant change in classification of final desmoplastic melanoma subtype (p<0.001). The proportion of desmoplastic melanoma was also significantly different between the initial and excisional biopsies (p=0.004). Forty-eight (48/101) patients had a SLNB, of which two (4.5%) were positive for metastatic melanoma; both cases were PDM in the excision specimen. Of the 10 cases demonstrating MDM in the excision specimen, the initial biopsy was a punch biopsy in six cases, shave biopsy in two cases and subcutaneous tissue was sampled in two patients (one punch biopsy, one incisional biopsy). Four of these 10 patients underwent SLNB which was negative in all cases. Twenty-two patients developed recurrence in the follow-up period (median 30 months, range 1-192 months), three with MDM in their excision specimen. One patient did not have a SLNB and developed regional lymph node recurrence. In this study there was a 10% risk that the percentage of desmoplastic melanoma in an initial biopsy of PDM was not representative of the entire lesion, resulting in reclassification as MDM in the excision specimen. If a SLNB is not performed in such cases, a positive SLNB may be missed (one patient in our study) which could impact treatment options for the patient. We recommend caution in not offering a SLNB in the setting of an initial biopsy of PDM if the biopsy is small compared with the overall lesion. If a SLNB is not procured at the time of wide excision in such cases, the SLNs should still be mapped by lymphoscintigraphy to facilitate careful follow up and to enable earlier detection and treatment of nodal disease.

Interobserver agreement in the histopathological classification of desmoplastic melanomas

Desmoplastic melanoma is a subtype of melanoma characterised by amelanotic fusiform melanocytes dispersed in a collagenous stroma. Cell-poor and fibrous stroma-rich 'pure' variants have been distinguished from 'mixed' variants with areas of higher cell density and/or less desmoplastic stroma. This distinction is relevant because patients whose tumours display a pure phenotype have a lower risk for regional lymph node metastasis and distant recurrence. However, little is known about interobserver agreement among pathologists in the subclassification of desmoplastic melanoma. To address this issue, we conducted a study in which eleven dermatopathologists independently evaluated whole slide scanned images of excisions from 30 desmoplastic melanomas. The participating pathologists were asked to classify the tumours as pure or mixed. They were also asked to record the presence or absence of neurotropism and angiotropism. We found substantial interobserver agreement between the 11 dermatopathologists in the classification of tumours as pure versus mixed desmoplastic melanoma (kappa=0.64; p<0.0001). There was fair agreement between the 11 dermatopathologists in the evaluation of presence versus absence of neurotropism (kappa=0.26; p<0.0001), and slight agreement in the assessment of angiotropism (kappa=0.13; p<0.0001). The level of concordance in the subclassification of desmoplastic melanomas is encouraging for the acceptance of this prognostic parameter in the real-world practice of melanoma pathology.

Desmoplastic melanoma: a review of its pathology and clinical behaviour, and of management recommendations in published guidelines

Desmoplastic melanomas are uncommon. Their behaviour differs from that of other melanoma subtypes; therefore, management guidelines for non-desmoplastic melanomas may not be applicable. This review sought to examine all available evidence relating to the behaviour and management of desmoplastic melanomas, based on review of all relevant English-language publications, and to critically assess the recommendations for their management in current published melanoma management guidelines. Compared with other melanoma subtypes, patients with 'pure' desmoplastic melanomas (where ≥90% of the invasive melanoma is of desmoplastic melanoma subtype) have much lower rates of sentinel node positivity and distant metastasis. Local recurrence rates are higher for desmoplastic melanomas, but resection margins wider than those recommended for non-desmoplastic melanomas have not been shown to be of benefit. Adjuvant radiotherapy reduces the risk of local recurrence when a satisfactory histological clearance (≥8 mm) cannot be achieved. Of 29 published melanoma management guidelines identified, only 11 specified management for desmoplastic melanomas, while seven simply stated that the feature should be reported. Desmoplastic melanoma is a unique melanoma subtype with biology that differs from that of other melanoma subtypes. It requires specific management strategies but few current guidelines address these.

Pitfalls in the diagnosis of lentigo maligna and lentigo maligna melanoma, facts and an opinion

Lentigo maligna/lentigo maligna melanoma (LM/LMM) affects chronically sun-damaged skin of the head and neck with a slow radial growth phase. It is characterised by predominantly lentiginous proliferation of small, but atypical melanocytes with occasional upward scatter in an atrophic epidermis. It is not uncommon for pathologists to receive partial or scouting biopsies to assess for LM. This makes the interpretation of symmetry and circumscription of the lesions challenging. Therefore, both cytologic and architectural criteria should be taken into consideration to render an accurate diagnosis of melanoma. Moreover, pathologists should be vigilant to avoid missing invasion, as this can change the treatment plan and prognosis. Herein, we aim to discuss important pitfalls in the diagnosis of LMM and its invasive component. Some of these caveats are differentiating between true invasion versus adnexal involvement by the in situ component or an incidental intradermal nevus, detection of microinvasion and multifocal invasion, and recognition of desmoplastic/spindle cell melanoma component.

Pathological review of primary cutaneous malignant melanoma by a specialist skin cancer multidisciplinary team improves patient care in the UK

AIMS

The National Institute for Health and Care Excellence advocated the development of specialist skin cancer multidisciplinary teams (SSMDTs) for the management of higher risk invasive skin cancers in the UK. The interobserver variability in the histopathological assessment of primary cutaneous malignant melanoma (PCMM) is well recognised.

METHODS

We evaluated the discordance rates in the assessment of the histopathological criteria of PCMM based on the eighth American Joint Committee on Cancer (AJCC) melanoma staging system and subsequent change in prognosis and management following pathology review by an SSMDT.

RESULTS

353 cases of PCMM were referred to our SSMDT between April 2015 and May 2016. Cases in which there was a discrepancy in one or more histological parameters following expert review were collected retrospectively. Of 341 eligible cases, there were 94 (27.6%) in which there was an alteration in any parameter. There was interobserver agreement in final diagnosis in 96.8%, Breslow thickness in 86.8%, ulceration in 98.2%, microsatellites in 98.5%, tumour mitotic rate in 88.9%, histological subtype in 92.4%, growth phase in 98.5%, angiolymphatic invasion in 97.7%, perineural invasion in 98.8%, regression in 95.3% and tumour-infiltrating lymphocytes in 95.0%. A corresponding change in AJCC stage occurred in 23 cases (6.7%), with a resulting change in clinical management in 10 cases (2.9%).

CONCLUSIONS

Disagreements in the pathological assessment of PCMM can have significant clinical implications for a small number of patients. Our findings highlight the value of the SSMDT for high-quality care of patients with melanoma in the UK.

Neurotropic melanoma: an analysis of the clinicopathological features, management strategies and survival outcomes for 671 patients treated at a tertiary referral center

Neurotropic cutaneous melanoma is a rare melanoma subtype that invades nerves and is often associated with desmoplastic melanoma. Limited data suggest that it has a greater propensity to recur locally, but it is unknown whether its behavior differs from that of other melanoma subtypes, including desmoplastic melanoma. We investigated clinicopathological predictors of outcome in a cohort of 671 patients with neurotropic melanoma to develop evidence-based management recommendations. Patients with primary neurotropic melanoma diagnosed from 1985 to 2013 were identified from the Melanoma Institute Australia database, along with a control cohort of 718 non-neurotropic melanoma patients. Features predictive of sentinel lymph node status, recurrence, melanoma-specific survival and response to adjuvant radiotherapy were sought. Neither local recurrence (hazard ratio: 1.28 (0.73-2.25) P=0.39) nor melanoma-specific survival (hazard ratio: 0.79 (0.55-1.15) P=0.22) were significantly affected by the presence of neurotropism on multivariate analysis. However, there was a markedly reduced likelihood of sentinel node positivity (hazard ratio: 0.61 (0.41-0.89) P=0.01) in neurotropic melanoma patients. Surgical margins ≥8mm halved the recurrence risk compared with <2 mm margins (hazard ratio: 0.46 (0.31-0.68) P<0.001). Additionally, in neurotropic melanoma patients with <8 mm margins, adjuvant radiotherapy halved the recurrence risk (hazard ratio: 0.48 (0.27-0.87) P=0.02). This, the largest study of neurotropic melanoma reported to date, has demonstrated that the presence of neurotropism does not alter the risk of melanoma recurrence or survival but does reduce the likelihood of sentinel node positivity. For successful treatment of neurotropic melanoma, adequate excision margins are of paramount importance. However, when adequate margins cannot be achieved, adjuvant radiotherapy reduces the risk of recurrence.

Lower Extremity Desmoplastic Malignant Melanoma in Egypt

Desmoplastic melanoma (DM) is a type of spindle cell melanoma characterized by the absence of pigment. The clinical diagnosis of DM represents a challenge for the practitioner and the pathologists because it can mimic benign or malignant skin tumors and even inflammatory skin disorders. We here discuss a case of a patient presented with multiple nodular lesions of the lower extremity following electrocautary to a lesion in her sole which was misdiagnosed as planter wart. Our clinical diagnosis was Kaposi sarcoma, hypertrophic lichen, or extensive verruca vulgaris. However, histopathological examination showed spindle-shaped cells positive for Melan-A and S100 revealing the diagnosis of DM.

Perineural Invasion of the Orbit by Neurotropic Nondesmoplastic Melanoma

The authors report a case of neurotropic nondesmoplastic melanoma involving the ophthalmic division of the trigeminal nerve and the cavernous sinus in a patient with recurrent scalp melanoma. This case highlights the importance of earlier diagnosis of local recurrence of melanoma and the rare association of neurotropic melanoma and orbital metastasis.

Performance Testing of RREB1, MYB, and CCND1 Fluorescence In Situ Hybridization in Spindle-Cell and Desmoplastic Melanoma Argues for a Two-Step Test Algorithm

BACKGROUND

Diagnostic confirmation of spindle-cell melanoma (SM) or desmoplastic melanoma (DM) as a melanoma can be challenging. In conventional melanoma (CM), a recently established fluorescence in situ hybridization (FISH) assay for RREB1, MYB, CCND1 can be helpful. Here, we determined the presence of RREB1, MYB, and CCND1 abnormalities in an SM/DM/mixed cohort.

METHODS

We assembled 49 cases and performed 3 separate hybridizations for RREB1/MYB/CCND1. We assessed clinical utility in diagnostically challenging cases and performed a cost and turnaround time analysis.

RESULTS

With regard to the diagnosis of melanoma, the FISH assay is 76% sensitive (n = 31/41 true positives melanomas) and 88% specific (n = 1/8 false positive desmoplastic nevi). The prevalence of abnormalities in DM is lower (12/19 cases, 63%; P = .03) than in SM (15/18 cases, 83%; P = .27), mixed (4 of 4 cases), or the reported sensitivity in CM (345/411 cases, 84%). The implied genetic differences in DM result in a higher false negative rate in DM (37%). Despite these limitations, when restricted to diagnostically challenging cases (n = 23), the FISH assay and, in particular, RREB1 was able to confirm melanoma in 70% (n = 16/23). Individual probe sensitivities ( RREB1 > MYB > CCND1) and a cost and turnaround time analysis argues for a 2-step test algorithm that reduces the economic impact of FISH testing considerably (~55%; n = 69 vs 123 hybridizations).

CONCLUSION

We propose a step-by-step genetic testing algorithm to support the diagnosis of melanoma in the setting of SM/DM and show that FISH testing is useful in diagnostically challenging cases.

Roles of adjuvant and salvage radiotherapy for desmoplastic melanoma

Current guidelines are unclear as to the precise role of radiotherapy (RT) in patients with desmoplastic melanoma (DM). The purpose of this study was to evaluate our institutional outcomes in patients with DM, and to explore the roles of both adjuvant and salvage RT in these patients. We identified 100 patients with a histopathologic diagnosis of DM who received treatment at our institution from 2000 to 2014. Local control, distant metastasis-free survival, and overall survival (OS) were evaluated in the 95 patients managed surgically with or without adjuvant and/or salvage RT. The overall rate of local recurrence (LR) was 10%. There was no LR in either adjuvant or salvage RT cohort. Adjuvant RT did not significantly improve LR-free survival at 5 years (100 vs. 81%, P=0.59), despite the RT patients having worse pathological features. Four of seven (57%) salvage patients developed distant metastases, despite 100% local control. Adjuvant RT did not significantly impact 5-year overall survival (86 vs. 82%, P=0.43). RT shows a trend towards improved local control in both the adjuvant and salvage settings for patients with DM, and likely overcomes adverse risk factors after surgery in appropriately selected patients. Future prospective studies are needed to better address the optimal management for these patients.

Melanoma: Clinical Presentations

The malignant cell in melanoma is the melanocyte. Because melanocytes are located in the basal layer of the epidermis, melanoma is most commonly seen on the skin. However, melanoma can also arise on mucosal surfaces such as the oral cavity, the upper gastrointestinal mucosa, the genital mucosa, as well as the uveal tract of the eye and leptomeninges. Melanomas tend to be pigmented but can also present as pink or red lesions. They can mimic benign or other malignant skin lesions. This chapter presents the spectrum of typical and less typical presentations of melanoma, as well as patterns of spread. It is divided into (1) cutaneous lesions; (2) patterns of regional spread, (3) non-cutaneous lesions; and (4) distant metastases.

Mutational dichotomy in desmoplastic malignant melanoma corroborated by multigene panel analysis

Desmoplastic malignant melanoma is a distinct melanoma entity histologically subtyped into mixed and pure forms due to significantly reduced lymph node metastases in the pure form. Recent reports investigating common actionable driver mutations have demonstrated a lack of BRAF, NRAS, and KIT mutation in pure desmoplastic melanoma. In search for alternative driver mutations next generation amplicon sequencing for hotspot mutations in 50 genes cardinal to tumorigenesis was performed and in addition the RET G691S polymorphism was investigated. Data from 21 desmoplastic melanomas (12 pure and 9 mixed) were retrieved. Pure desmoplastic melanomas were either devoid of mutations (50%) or displayed mutations in tumor suppressor genes (TP53, CDKN2A, and SMAD4) singularly or in combination with the exception of a PIK3CA double-mutation lacking established biological relevance. Mixed desmoplastic melanomas on the contrary were frequently mutated (89%), and 67% exhibited activating mutations similar to common-type cutaneous malignant melanomas (BRAF, NRAS, FGFR2, and ERBB2). Separate analysis of morphologically heterogeneous tumor areas in four mixed desmoplastic malignant melanomas displayed no difference in mutation status and RET G691 status. GNAQ and GNA11, two oncogenes in BRAF and NRAS wild-type uveal melanomas, were not mutated in our cohort. The RET G691S polymorphism was found in 25% of pure and 38% of mixed desmoplastic melanomas. Apart from RET G691S our findings demonstrate absence of activating driver mutations in pure desmoplastic melanoma beyond previously investigated oncogenes (BRAF, NRAS, and KIT). The findings underline the therapeutic dichotomy of mixed versus pure desmoplastic melanoma with regard to activating mutations primarily of the mitogen-activated protein kinase pathway.

A nuclear circularity-based classifier for diagnostic distinction of desmoplastic from spindle cell melanoma in digitized histological images

Context:

Distinction of spindle cell melanoma (SM) and desmoplastic melanoma (DM) is clinically important due to differences in metastatic rate and prognosis; however, histological distinction is not always straightforward. During a routine review of cases, we noted differences in nuclear circularity between SM and DM.

Aim:

The primary aim in our study was to determine whether these differences in nuclear circularity, when assessed using a basic ImageJ-based threshold extraction, can serve as a diagnostic classifier to distinguish DM from SM.

Settings and Design:

Our retrospective analysis of an established patient cohort (SM n = 9, DM n = 9) was employed to determine discriminatory power.

Subjects and Methods:

Regions of interest (total n = 108; 6 images per case) were selected from scanned H and E-stained histological sections, and nuclear circularity was extracted and quantified by computational image analysis using open source tools (plugins for ImageJ).

Statistical Analysis:

Using analysis of variance, t-tests, and Fisher's exact tests, we compared extracted quantitative shape measures; statistical significance was defined as P < 0.05.

Results:

Classifying circularity values into four shape categories (spindled, elongated, oval, round) demonstrated significant differences in the spindled and round categories. Paradoxically, DM contained more spindled nuclei than SM (P = 0.011) and SM contained more round nuclei than DM (P = 0.026). Performance assessment using a combined shape-classification of the round and spindled fractions showed 88.9% accuracy and a Youden index of 0.77.

Conclusions:

Spindle cell melanoma and DM differ significantly in their nuclear morphology with respect to fractions of round and spindled nuclei. Our study demonstrates that quantifying nuclear circularity can be used as an adjunct diagnostic tool for distinction of DM and SM.

Enhanced immunohistochemical detection of neural infiltration in primary melanoma: is there a clinical value?

Neural infiltration in primary melanoma is a histopathologic feature that has been associated with desmoplastic histopathologic subtype and local recurrence in the literature. We tested the hypothesis that improved detection and characterization of neural infiltration into peritumoral or intratumoral location and perineural or intraneural involvement could have a prognostic relevance. We studied 128 primary melanoma cases prospectively accrued and followed at New York University using immunohistochemical detection with antihuman neurofilament protein and routine histology with hematoxylin and eosin. Neural infiltration, defined as the presence of tumor cells involving or immediately surrounding nerve foci, was identified and characterized using both detection methods. Neural infiltration rate of detection was enhanced by immunohistochemistry for neurofilament in matched-pair design (47% by immunohistochemistry versus 25% by routine histology). Immunohistochemical detection of neural infiltration was significantly associated with ulceration (P = .021), desmoplastic and acral lentiginous histologic subtype (P = .008), and head/neck/hands/feet tumor location (P = .037). Routinely detected neural infiltration was significantly associated with local recurrence (P = .010). Immunohistochemistry detected more intratumoral neural infiltration cases compared with routine histology (30% versus 3%, respectively). Peritumoral and intratumoral nerve location had no impact on clinical outcomes. Using a multivariate model controlling for stage, neither routinely detected neural infiltration nor enhanced immunohistochemical characterization of neural infiltration was significantly associated with disease-free or overall survival. Our data demonstrate that routinely detected neural infiltration is associated with local recurrence in all histologic subtypes but that improved detection and characterization of neural infiltration with immunohistochemistry in primary melanoma does not add to prognostic relevance.

A diagnostic algorithm to distinguish desmoplastic from spindle cell melanoma

Spindle cell melanoma and desmoplastic melanoma differ clinically in prognosis and therapeutic implications; however, because of partially overlapping histopathological features, diagnostic distinction of spindle cell from desmoplastic melanoma is not always straightforward. A direct comparison of diagnostic and therapeutic biomarkers has not been performed. Meta-review of the literature discloses key clinicopathological differences between spindle cell and desmoplastic melanoma, including immunophenotypes. Using 50 biomarkers available in routine diagnostics, we examined 38 archival cases (n=16 spindle, 18 desmoplastic, 4 mixed spindle/desmoplastic melanoma). S100 remains as the most reliable routine marker to reach the diagnosis of melanoma in spindle cell and desmoplastic melanoma. We identified nine distinctly labeling markers with spindle cell melanoma showing positivity for laminin, p75, HMB45, c-kit, and MelanA, and desmoplastic melanoma preferentially labeling with collagen IV, trichrome, CD68, and MDM2. On the basis of comparisons of test performance measures, MelanA and trichrome were used to devise a 94% sensitive diagnostic algorithm for the distinction of desmoplastic from spindle cell melanoma. Gene amplification and expression status was assessed for a set of potentially drugable targets (HER2, EGFR, MET, MDM2, TP53, ALK, MYC, FLI-1, and KIT). Fluorescent in situ hybridizations did not reveal a significant number of gene aberrations/rearrangements; however, protein overexpression for at least one of these markers was identified in 35 of 38 cases (92%). In addition, we found BRAF mutations in 31% of spindle cell and 5% of desmoplastic melanoma, with an overall mutation frequency of 16% (n=6/38). We present the first comprehensive screening study of diagnostic and therapeutic biomarkers in spindle cell and desmoplastic melanoma. The devised algorithm allows diagnostic distinction of desmoplastic from spindle cell melanoma when routine histology is not decisive.

Malignant melanoma with neural differentiation: an exceptional case report and brief review of the pertinent literature

: The term neurotropic melanoma has been used to refer to malignant melanoma with associated infiltration of nerve or "neural differentiation"--that is, melanoma cells exhibiting cytological characteristics of nerve cells. Historically, neurotropic melanoma has generally been discussed within the context of desmoplastic melanoma. We report an exceptional case of melanoma notable for a very well-differentiated neural component that was contiguous with obvious overlying melanoma. After careful consideration of all pertinent histological features, the overall diagnostic impression was that of melanoma with associated "malignant neurotization." We have not encountered a previously reported case with such a well-differentiated neural component. The following article details our exceptional case of melanoma with "malignant neurotization" and presents a discussion of the differential diagnosis and brief review of the pertinent literature.

Data set for pathology reporting of cutaneous invasive melanoma: recommendations from the international collaboration on cancer reporting (ICCR)

An accurate and complete pathology report is critical for the optimal management of cutaneous melanoma patients. Protocols for the pathologic reporting of melanoma have been independently developed by the Royal College of Pathologists of Australasia (RCPA), Royal College of Pathologists (United Kingdom) (RCPath), and College of American Pathologists (CAP). In this study, data sets, checklists, and structured reporting protocols for pathologic examination and reporting of cutaneous melanoma were analyzed by an international panel of melanoma pathologists and clinicians with the aim of developing a common, internationally agreed upon, evidence-based data set. The International Collaboration on Cancer Reporting cutaneous melanoma expert review panel analyzed the existing RCPA, RCPath, and CAP data sets to develop a protocol containing "required" (mandatory/core) and "recommended" (nonmandatory/noncore) elements. Required elements were defined as those that had agreed evidentiary support at National Health and Medical Research Council level III-2 level of evidence or above and that were unanimously agreed upon by the review panel to be essential for the clinical management, staging, or assessment of the prognosis of melanoma or fundamental for pathologic diagnosis. Recommended elements were those considered to be clinically important and recommended for good practice but with lesser degrees of supportive evidence. Sixteen core/required data elements for cutaneous melanoma pathology reports were defined (with an additional 4 core/required elements for specimens received with lymph nodes). Eighteen additional data elements with a lesser level of evidentiary support were included in the recommended data set. Consensus response values (permitted responses) were formulated for each data item. Development and agreement of this evidence-based protocol at an international level was accomplished in a timely and efficient manner, and the processes described herein may facilitate the development of protocols for other tumor types. Widespread utilization of an internationally agreed upon, structured pathology data set for melanoma will lead not only to improved patient management but is a prerequisite for research and for international benchmarking in health care.

The importance of adequate primary tumor excision margins and sentinel node biopsy in achieving optimal locoregional control for patients with thick primary melanomas

OBJECTIVE

This study sought to investigate the impact of histopathologically measured excision margins and SNB on local and locoregional disease control in patients with primary cutaneous melanomas more than 4 mm thick.

BACKGROUND

Most current guidelines recommend at least a 2-cm surgical margin (which corresponds to a 16-mm histopathologic margin). These guidelines are based on limited evidence, mostly obtained in patients who did not have an SNB.

METHODS

Histopathologic tumor excision margins for clinically lymph node-negative patients with melanomas more than 4 mm thick, treated at Melanoma Institute Australia (1992-2009), were determined. Clinicopathologic predictors of local and locoregional disease-free survival were investigated.

RESULTS

There were 632 patients eligible for the study; of these, 397 (62.8%) had an SNB. The median histopathologic excision margin was 15 mm (interquartile range, 11.0-19.5 mm). After a median follow-up of 37 months, local and locoregional recurrences were observed in 48 (7.6%) and 159 (25.2%) patients, respectively. Excision margin as a continuous variable was a significant predictor of local [hazard ratio (HR), 0.91; P < 0.001) and locoregional (HR, 0.97; P = 0.042) tumor control on multivariate analyses. Patients with histopathologic margins 16 mm or less had worse local disease-free survival (HR, 2.41; P = 0.01). Patients who did not have an SNB were at higher risk of locoregional recurrence (HR, 1.67; P = 0.003).

CONCLUSIONS

Histopathologically determined primary tumor excision margins more than 16 mm, corresponding to 2-cm surgical margins, were associated with better local control in patients with melanomas more than 4 mm thick. Patients achieved the best local and locoregional control when SNB was coupled with a more than 16-mm histologic excision margin.

Desmoplastic melanoma: a review

Desmoplastic melanoma (DM) is a variant of spindle cell melanoma typically found on chronically sun-damaged skin of older individuals. Early diagnosis can be challenging because it is often amelanotic and has a predominantly dermal component. DM can be difficult to diagnose not only clinically but also histologically, and can be mistaken for a variety of benign and malignant nonmelanocytic spindle cell tumors when viewed on prepared histopathology slides. Pathologists have observed that DMs can manifest significant variation with respect to the extent of intratumoral cellularity, fibrosis, and/or perineural invasion. Furthermore, some tumors present with a pure desmoplastic invasive component (>90%) while other tumors display mixed features of DM and nondesmoplastic melanoma. This has led to the separation of DM into 2 histologic subtypes, pure and mixed. With a focus on the distinction between pure and mixed DM, this review will detail what is currently known about the diagnostic features of DM, discuss risk and prognostic factors, and examine the current literature on disease progression and management.

Desmoplastic malignant melanoma: a study of ten cases and status of BRAF mutation

BACKGROUND

Desmoplastic malignant melanoma (DM) is a rare variant of melanoma. BRAF gene mutations have been poorly explored in this entity.

OBJECTIVE

To detect BRAF gene mutation in a series of DM.

METHODS

This is a single-center retrospective study of ten patients with DM, with a biomolecular analysis of BRAF mutation.

RESULTS

The male:female ratio was 2.3:1, with a mean patient age of 66.5 years. Melanoma arose in the head and neck region in 3 cases. The mean tumor thickness was 7.97 mm, Clark level was IV or V in all cases. Six melanomas were of the pure DM variant. Three patients had at least one local recurrence, two had regional node metastases, and two experienced systemic metastases which they died of (average follow-up 34.1 months). A V600E BRAF mutation was detected in only one patient.

CONCLUSION

BRAF mutation seems to be a rare event in DM contrary to other melanoma variants.

Neurotropic melanoma: the management of localised disease

Neurotropic melanoma is a rare subtype of cutaneous malignant melanoma. Compared with conventional melanoma, it is more locally aggressive with an increased tendency for local recurrence but less likely for nodal or distant metastases. These tumours can be a diagnostic dilemma with a variety of morphological, histopathological, and immunophenotypical expressions. The often amelanotic, benign appearance may lead to treatment issues such as late presentation, diagnostic delay, misdiagnosis, insufficient surgical margins, and recurrence with resulting poor outcome. The neurotropic nature of the disease and prevalence in the head and neck region can result in perineural and neural invasion along named large nerves into the brain with resulting neuropathies. Wide local excision with adjuvant radiotherapy where indicated remains the current practice for treatment with chemotherapy predominately being reserved as a salvage treatment for patients with disseminated disease.

[Histology of malignant tumors caused by UV light]

Chronic exposure to UV light is the most important etiological factor for the occurrence of malignant skin tumors. Light-skinned persons who for professional reasons or in leisure activities are exposed to sunlight without sun protection for long periods of time are particularly at risk. This article gives a summary of the histopathology of malignant skin tumors caused by UV light.

Desmoplastic melanocytic nevi with lymphocytic aggregates

Desmoplastic melanocytic nevi can be difficult to distinguish from desmoplastic melanoma. The presence of lymphocytic aggregates in association with a sclerosing melanocytic proliferation is commonly regarded as a feature in support of a diagnosis of desmoplastic melanoma. However, the finding is not specific for melanoma. Herein we report six cases of sclerosing melanocytic nevi with associated lymphocytic aggregates. They occurred in five women and one man, ranging in age from 11 to 61 years. Three lesions were sclerosing Spitz nevi; one was an amelanotic sclerosing blue nevus, one an acquired intradermal sclerosing nevus, and one was a congenital compound melanocytic nevus with sclerosis of its dermal component. The lesions were interpreted as benign, i.e. melanocytic nevi, because of their histopathologic attributes (symmetric silhouette, benign cytologic features) and results from immunohistochemical studies (all lesions strongly expressed Melan-A and p16) and fluorescence in situ hybridization (FISH). Three lesions tested by FISH lacked copy number changes of 11p, 6q or 6p. None of the lesions recurred. The cases highlight that contextual information is essential for the diagnosis of desmoplastic melanoma and sclerosing nevus. The presence of lymphocytic aggregates per se does not prove that a sclerosing melanocytic proliferation is malignant.

Identification of TFG (TRK-fused gene) as a putative metastatic melanoma tumor suppressor gene

High density SNP arrays can be used to identify DNA copy number changes in tumors such as homozygous deletions of tumor suppressor genes and focal amplifications of oncogenes. Illumina Human CNV370 Bead chip arrays were used to assess the genome for unbalanced chromosomal events occurring in 39 cell lines derived from stage III metastatic melanomas. A number of genes previously recognized to have an important role in the development and progression of melanoma were identified including homozygous deletions of CDKN2A (13 of 39 samples), CDKN2B (10 of 39), PTEN (3 of 39), PTPRD (3 of 39), TP53 (1 of 39), and amplifications of CCND1 (2 of 39), MITF (2 of 39), MDM2 (1 of 39), and NRAS (1 of 39). In addition, a number of focal homozygous deletions potentially targeting novel melanoma tumor suppressor genes were identified. Because of their likely functional significance for melanoma progression, FAS, CH25H, BMPR1A, ACTA2, and TFG were investigated in a larger cohort of melanomas through sequencing. Nonsynonymous mutations were identified in BMPR1A (1 of 43), ACTA2 (3 of 43), and TFG (5 of 103). A number of potentially important mutation events occurred in TFG including the identification of a mini mutation "hotspot" at amino acid residue 380 (P380S and P380L) and the presence of multiple mutations in two melanomas. Mutations in TFG may have important clinical relevance for current therapeutic strategies to treat metastatic melanoma.

Desmoplastic melanoma

Desmoplastic melanoma (DM) is a variant of spindle cell melanoma characterized by the presence of abundant fibrous matrix. It is typically found in the head and neck region on chronically sun-damaged skin of older individuals. Early detection is uncommon, because its clinical features are not distinctive. DM is prone to misdiagnosis not only clinically but also histologically. It may simulate a sclerosing melanocytic nevus and various benign and malignant nonmelanocytic lesions. Among melanomas said to be desmoplastic by various pathologists there is significant variation with regard to the extent of intratumoral fibrosis. It may be prominent throughout the entire tumor (pure DM) or represent a portion of an otherwise nondesmoplastic melanoma (combined DM). Immunophenotypically, DM are usually strongly and homogeneously positive for S-100 protein, but are often negative or only focally positive for melanocyte differentiation antigens. DM differs from conventional melanoma in its clinical course. It is associated with a higher tendency for local recurrence, but metastases to regional lymph nodes are less common.

Clinical and pathological features of metastases of primary cutaneous desmoplastic melanoma

AIMS

Primary cutaneous desmoplastic melanoma (DM) may be entirely desmoplastic ['pure' DM (pDM)] or exhibit a desmoplastic component admixed with a non-desmoplastic component ['combined' DM (cDM)]. Our aim was to describe the histological features of metastases of primary DM and to determine whether they were predictive of outcome.

METHODS

The effect of clinicopathological parameters on overall survival (OS) was analysed, and the correlation between histological features of the primary melanoma and metastases was studied in patients with metastatic DM.

RESULTS

Twenty-six patients (18 males; eight females) developed 50 metastases in sentinel nodes (13; 26.0%), regional nodes (10; 20.0%), skin (14; 28.0%), and distant sites (13; 26.0%). The cellular composition of metastases correlated with that of the corresponding primary tumours. Time to development of first non-sentinel lymph node metastasis was shorter in cDM than in pDM (median 11.2 versus 24.9 months, P = 0.075). The only independent predictors of poorer OS were cDM type [hazard ratio 6.17, 95% confidence interval (CI) 1.61-23.81, P = 0.008] and male sex (hazard ratio 5.98, 95% CI 1.34-26.66, P = 0.019).

CONCLUSIONS

The cellular composition of primary DM correlates with that of metastatic DM and with outcome. It is important to consider the possibility of primary or metastatic DM when examining tumours composed of spindle cells.

Evolving concepts in melanoma classification and their relevance to multidisciplinary melanoma patient care

In the initial period after melanoma was recognised as a disease entity in the early 1800's, it was subclassified on the basis of its presumed origin (from a precursor naevus, from a melanocytic precursor lesion acquired during adult life or in previously blemish-fee skin). In 1967 the eminent American pathologist, Dr Wallace Clark, proposed a histogenetic classification for melanoma in which the disease was subdivided predominantly on the basis of histopathological features of the intra-epidermal component of the tumour adjacent to any dermal invasive component. The subtypes were superficial spreading melanoma (SSM), lentigo maligna melanoma (LMM) and nodular melanoma (NM). Whilst additional entities, including acral lentiginous melanoma, mucosal melanoma, desmoplastic melanoma and naevoid melanoma have since been recognised, SSM, LMM and NM remain in the latest (2006) version of the WHO melanoma classification. Clark's histogenetic classification has been criticised because the criteria upon which it is based include clinical features (such as the site of the melanoma) and non-tumourous histopathological features (such as the character of the associated epidermis and the degree of solar elastosis) and also because of overlap in defining features, lack of an independent association with patient outcome and minimal relevance as a determinant of clinical management. However, such criticisms fail to acknowledge its importance in highlighting the myriad of clinical and histological guises of melanoma, which if not recognized by clinicians and pathologists will inevitably lead to a delay in diagnosis and a concomitant adverse clinical outcome. Recently, mutually exclusive oncogenic mutations in melanomas involving NRAS (15-20%), BRAF (50%), CKIT (2%), and GNAQ/GNA11 (50% of uveal melanomas) have been identified. This might herald the beginning of a new molecular classification of melanoma in which the biologically distinct subsets share a common oncogenic mechanism, behave clinically in a similar fashion and require similar clinical management. These discoveries are already being successfully exploited as therapeutic targets in clinical trials of metastatic melanoma patients with promising activity. Whilst there remains much to be discovered in this rapidly evolving field, there is already great optimism that more rational and effective therapies for melanoma patients will soon be widely available.

Pure desmoplastic melanoma: a melanoma with distinctive clinical behavior

OBJECTIVE

The purpose of the study was to evaluate the excision margin necessary for desmoplastic melanoma (DM).

BACKGROUND

DM consists of 2 histologic subtypes, pure DM (PDM) and mixed DM (MDM), differing in extent of fibrotic component. We investigated clinical and therapeutic determinants of prognosis in these DM entities.

METHODS

We reviewed 118 PDM and 124 MDM treated at our Institute over 25 years. Local relapse, distant metastasis, and survival were studied.

RESULTS

Most (91.7%) distant metastases in PDM developed after 1 or more local recurrences; whereas distant metastasis usually (79.6%) occurred as first event in MDM. Overall mortality trends in relation to lesion-thickness-plus-excision-width differed for PDM (P = 0.014) but not MDM (P = 0.185). For PDM, 5-year crude cumulative incidence (CCI) of mortality was higher (40.0%) for thin tumors (≤ 2 mm thick) excised with 1 cm margin than those excised with 2 cm (14.8%); CCI of mortality for PDM > 2 mm thick excised with 2 cm margins (13.4%) was similar to that for thin PDM lesions excised with 2 cm (14.8%). CCI of local recurrence was also greater in PDM excised with 1 cm margins. In MDM, mortality increased with stage but was independent of excision width (CCI: 29.4% for ≤ 2 mm/2 cm, 31.3% for ≤ 2 mm/1 cm, and 48.3% for > 2 mm/2 cm); a similar trend was found for MDM distant metastases.

CONCLUSIONS

In PDM, limited excision width is associated with significantly greater local recurrence and mortality; treatment should be excision with 2 cm margins even for thin lesions. MDM behaves similarly to other melanomas; treatment should follow guidelines on melanoma management.

Desmoplastic melanoma presenting as pyogenic granuloma: report of a case with review of literature

An elderly female patient was referred to the author for the treatment of a large recurrent pyogenic granuloma in the sole of right foot for a period of 2 years. She underwent excisional surgeries at an outside facility twice in the past. This time, she was treated with wide excision biopsy and the surgical defect was closed with a new technique, the "adjustable suture technique". Histopathology report confirmed "desmoplastic melanoma" with complete marginal clearance. The wound had healed uneventfully. There were no recurrences at 4-year follow-up.

Prognostic factors in cutaneous desmoplastic melanoma: a study of 252 patients

BACKGROUND

Desmoplastic melanoma (DM) is a rare subtype of melanoma that is characterized by malignant spindle cells separated by prominent, fibrocollagenous stroma. Primary melanomas either may be entirely desmoplastic or almost entirely desmoplastic (pure DM [pDM]) or may exhibit a desmoplastic component admixed with a nondesmoplastic component (combined DM [cDM]).

METHODS

Patients who were diagnosed between 1993 and 2007 at a single institution with clinically localized, primary cutaneous melanoma (PCM) that contained a desmoplastic component and who underwent sentinel lymph node (SLN) biopsy were identified. Clinical and pathologic features of the primary tumors were correlated with DM type, SLN status, and patient outcome.

RESULTS

Two hundred fifty-two patients (167 men, 85 women) were identified (median age, 61 years). The median tumor thickness was 2.0 mm. One hundred twenty-three patients (48.8%) had pDM, and 129 patients (51.2%) had cDM. Overall, 17 patients (6.7%) had positive SLN status, including 12 patients with cDM and 5 patients with pDM. Because of the low SLN-positive rate, a statistically significant difference in SLN status between patients with cDM (8.5%) and patients with pDM (4.9%; P = .25) could not be demonstrated. Older patient age, being a man, positive SLN status, and increasing tumor thickness were associated significantly with poorer disease-free survival (P < .05), although only the latter 2 variables were independently predictive. In addition, cDM type (P = .017) was associated significantly and independently with a shorter time to recurrence.

CONCLUSIONS

In this largest study to date of patients with DM who underwent SLN biopsy, the SLN-positive rate in patients with DM was lower than that in patients with conventional melanoma. The results indicated that DM type is associated significantly and independently with the time to recurrence and should be evaluated routinely in all patients with PCM. Cancer 2010. (c) 2010 American Cancer Society.