Cases Of Desmoplastic Melanoma Research Articles

Desmoplastic melanoma in Sweden in 2009-2022: Apopulation-based registry study demonstrating distinctive tumour characteristics, incidence and survival trends.

Desmoplastic melanoma (DM) is a rare subtype, accounting for less than 5% of primary cutaneous invasive melanomas. DM often arises in chronically sun-exposed skin, in older individuals. While the incidence of cutaneous melanoma has increased globally, trends specific to DM are less documented and studies on survival outcomes for DM are inconsistent. To study patient and tumour characteristics, incidence trends and survival outcomes of desmoplastic melanoma in comparison with other melanoma subtypes using data from the population-based Swedish Melanoma Registry (SweMR). Clinicopathological variables were obtained from SweMR, for patients diagnosed with invasive cutaneous melanomas diagnosed in Sweden from 2009 to 2022. Incidence rates of DM per 100,000 inhabitants were calculated. DM cases were identified and survival outcomes were compared across DM, superficial spreading melanoma (SSM), nodular melanoma (NM) and lentigo maligna melanoma (LMM). Survival was analysed using Kaplan-Meier and Cox regression methods. Among 48,945 invasive melanomas, 388 (0.8%) were identified as DM. The incidence ranged between 0.1 and 0.4 cases per 100,000, without a evident rise, beside a certain peak in 2019-2020 in the men. DM had compared to other melanoma subtypes the thickest primary tumours (p < 0.001). When adjusting for baseline prognostic factors, DM patients had an improved melanoma-specific survival (HR 0.36, 95% CI 0.26-0.49). No significant improvement in survival was observed for DM diagnosed in 2015-2022 compared to those diagnosed in 2009-2014 (adjusted HR 0.99, 95% CI 0.45-2.14), whereas other subtypes showed an improvement (adjusted HR 0.74, 95% CI 0.68-0.80). In contrast to the rising incidence of other melanoma subtypes, the incidence of DM has remained more stable over recent years. Despite presenting with adverse prognostic features, survival from DM is superior when adjusting for these factors. However, the introduction of anti-PD-1 therapy has not significantly improved survival for DM patients.

Pure and Mixed Variants of Desmoplastic Melanoma: A Single-Center, Retrospective, Clinicopathologic Review.

Desmoplastic melanoma (DM) is a rare melanoma variant. Prognostic indicators and survival vary widely and are further confounded by the histopathologic distinction between pure DM (pDM) and mixed DM (mDM) subtypes. The utility of current treatment guidelines is limited by the lack of evidence-based recommendations. To compare the clinicopathologic characteristics of pure and mixed subtypes of DMs. All cases of DM were identified from the Washington University in St Louis institutional pathology database between January 2000 and September 2022. Fifty-two cases were identified and subsequently categorized as pure ( n = 26) or mixed ( n = 26). Clinical and histopathologic data were collected and compared. There were no differences in demographics or tumor location between pure and mixed subtypes. Patients with mDM were more likely to have mitoses present ( p = .03). There were no differences in Breslow depth, tumor diameter, level of invasion, ulceration, and lymphovascular or perineural invasion. The utilization of sentinel lymph node biopsy ( p = .17) and sentinel lymph node positivity ( p = .67) were also similar. Despite histopathologic distinction between pDM and mDM, these subtypes were found to have similar clinicopathologic characteristics, including similar rates of sentinel lymph node metastasis.

Desmoplastic Melanoma: A Clinicopathological Analysis of Three Cases in the Chinese Population.

PurposeTo investigate the clinicopathological characteristics and immunophenotype of desmoplastic melanoma (DM) in the Chinese population.Patients and MethodsWe report three cases of DM diagnosed by the Pathology Department of Shanghai Dermatology Hospital. We describe the clinical and pathological characteristics of the three cases and examine molecular markers used in the diagnosis of DM. Finally, we summarize the current literature in the DM field.ResultsClinically, lesions in the three DM patients were characterized by non-pigmented nodules or papules. Microscopically, we observed an abundance of fibrous interstitium mixed with spindle cells exhibiting various degrees of atypia. Occasionally, these structures exhibited changes in lentigo maligna at the epidermal junction, accompanied by the presence of lymphoid follicular structures and neurophilic behavior. Diagnosis of DM was confirmed by immunohistochemical staining, which revealed high expression levels of S-100 and SOX-10. Melanocyte markers were focally positive or negative. Unlike DMs from other populations, our three patients were negative for WT-1 and P53. All three cases received surgical resection, which is the preferred treatment for DM, and none of the patients experienced recurrence.ConclusionDM in these Chinese patients was similar to that observed in other DM populations in terms of immunophenotype and clinical and histological features. A notable absence in p53 staining was observed in the three cases reported here, suggesting that p53 negativity should not exclude the diagnosis of DM in the Chinese population.

Desmoplastic melanoma: Demographic and clinicopathological features and disease-specific prognostic factors.

Desmoplastic melanoma (DM) is a rare morphological subtype of melanoma that remains uncharacterized. The aim of the present study was to investigate the incidence of DM, its general demographics, clinicopathological features and disease-specific prognostic factors. DM cases were sampled from the Surveillance, Epidemiology and End Results (SEER) program from between 1973 and 2017. A total of 3,657 cases (median age, 68 years) were identified. The results indicated that DM primarily occurred in Caucasian subjects, with a male-to-female ratio of 2:1. Statistically significant overall survival (OS) and disease-specific survival (DSS) rate differences were identified according to sex, age, treatment, T stage, N stage and SEER historic tumor stage (P<0.05). In multivariate Cox regression analysis, age >68 years, male sex, American Joint Committee on Cancer (AJCC) stage II and III, and SEER historic tumor stage of the regional tumor were all factors associated with poorer OS and DSS rates. The findings also revealed that surgical treatment was associated with favorable DSS and OS rates. In conclusion, DM occurred primarily in Caucasian subjects of 60–80 years of age, with predominance in males. Furthermore, age, sex, AJCC stage, SEER historic tumor stage and surgical treatment were identified as independent prognostic factors of DM in terms of DSS and OS.

Diagnostic utility of dual 5-hydroxymethylcytosine/Melan-A immunohistochemistry in differentiating nodal nevus from metastatic melanoma: An effective first-line test for the workup of sentinel lymph node specimen.

Distinguishing benign nodal nevus from metastatic melanoma can be diagnostically challenging, with important clinical consequences. Recently, the loss of epigenetic marker, 5-hydroxymethylcytosine (5-hmC) expression by immunohistochemistry has been found in melanomas and atypical melanocytic neoplasms. About 41 metastatic melanomas and 20 nodal nevi were retrieved. Nuclear 5-hmC (brown) and cytoplasmic Melan-A Red (red) double immunohistochemical staining was performed. Total or partial loss of nuclear expression of 5-hmC was noted in 40/41 metastatic melanomas; these tumor cells were strongly positive for Melan-A Red, except in one case of desmoplastic melanoma. All cases of nodal nevus showed uniformly retained nuclear expression of 5-hmC accompanied by strong Melan-A Red cytoplasmic staining. In two cases containing both nodal nevus and metastatic melanoma, all tumor cells were positive for Melan-A Red, but a nuclear expression of 5-hmC was selectively absent only in the melanoma tumor cells. Dual 5-hmC/Melan-A Red immunohistochemistry is highly specific in distinguishing nodal nevus from metastatic melanoma. Our protocol for brown and red chromogens used in this study provides excellent color contrast and is easy to interpret. Furthermore, this dual staining method allows the preservation of limited tumor tissue, which could be used for potential molecular studies.

A Case of Desmoplastic Melanoma in a Patient with Parkinson's Disease.

A Case of Desmoplastic Melanoma in a Patient with Parkinson's Disease.

A case of desmoplastic melanoma that was difficult to distinguish from malignant peripheral nerve sheath tumor

The clinical and pathological diagnosis of desmoplastic melanoma is difficult, because almost 50% of desmoplastic melanoma cases involve non-pigmented lesions and the tumor cells can resemble fibroblasts or Schwannian cells based on their frequent amelanotic features. Moreover, desmoplastic melanoma typically has low positive rates for melanoma markers, with the exception of the S-100 protein. We report the case of an 81-year-old Japanese man with an 8-mm desmoplastic melanoma. He initially noticed a painless and non-pigmented skin lesion that did not grow noticeably for 6months. It was unlikely that he had von Recklinghausen disease, and the mass was initially considered a dermatofibroma. Excisional biopsy revealed an intradermal mass, with the superficial portion mimicking neurofibroma and the deeper portion exhibiting nodular growth of sarcomatoid spindle cells. The tumor region lacked intradermal proliferation of atypical melanocytic cells, intracytoplasmic melanin, and expression of melanoma markers (except S-100 protein and Sox10). Although a malignant peripheral nerve sheath tumor derived from neurofibroma was possible, the slow growth with diffuse and strong immunoreactivity to the S-100 protein and Sox10 favored a diagnosis of desmoplastic melanoma. Pathologists should recognize that desmoplastic melanoma may not involve in situ lesions or the immunohistochemical expression of standard melanoma markers.

Detection of desmoplastic melanoma with dermoscopy and reflectance confocal microscopy.

Desmoplastic melanoma (DM) is frequently misdiagnosed clinically and often associated with melanoma in situ (MIS). To improve the detection of DM using dermoscopy and reflectance confocal microscopy (RCM). A descriptive analysis of DM dermoscopy features and a case-control study within a melanoma population for RCM feature evaluation was performed blindly, using data obtained between 2005 and 2015. After retrospectively identifying all DM cases with RCM data over the study period (n = 16), a control group of non-DM melanoma patients with RCM data, in a ratio of at least 3 : 1, was selected. The control group was matched by age and primary tumour site location, divided into non-DM invasive melanomas (n = 27) and MIS (n = 27). Invasive melanomas were selected according to the melanoma subtypes associated with the DM cases. The main outcomes were the frequency of melanoma-specific features on dermoscopy for DM; and the odds ratios of RCM features to distinguish DM from MIS and/or other invasive melanomas; or MIS from the combined invasive melanoma group. At least one of the 14 melanoma-specific features evaluated on dermoscopy was found in 100% of DMs (n = 15 DM with dermoscopy). Known RCM melanoma predictors were commonly found in the DMs, such as pagetoid cells (100%) and cell atypia (100%). The RCM feature of spindle cells in the superficial dermis was more common in DM compared with the entire melanoma control group (OR 3.82, 95% CI 1.01-14.90), and particularly compared to MIS (OR 5.48, 95% CI 1.11-32.36). Nucleated cells in the dermis and the RCM correlate of dermal inflammation were also significant RCM features favouring DM over MIS, as well as invasive melanoma over MIS. Dermoscopy and RCM may be useful tools for the identification of DM. Certain RCM features may help distinguish DM from MIS and other invasive melanomas. Larger studies are warranted.

Frequency of telomerase reverse transcripter promoter mutations in desmoplastic melanoma subtypes: analyses of 76 cases.

Estimates of the frequency of telomerase reverse transcripter (TERT) mutations in desmoplastic melanoma (DM) are limited. DM is categorized into subtypes, pure and mixed, differing in prognosis, suggesting genetic heterogeneity. Given this, our aims were to determine the incidence of TERT promoter mutations in DM subtypes and to evaluate its relationship with established histopathologic prognosticators, BRAF and RETp status, and neurofibromin protein expression. Of the archival annotated samples retrieved, 76 cases of DM (48 pure and 28 mixed) fulfilled the criteria for inclusion. PCR amplification of the TERT promoter region was performed on DNA extracted from formalin-fixed paraffin-embedded tissue using primers5'-GCCGATTCGACCTCTCTCC-3' (forward) and 5'-CAGCGCTGCCTGAAACTC-3' (reverse). For each case, appropriate C>T mutations were identified on the electropherograms. Univariate analysis using χ-test was carried out to identify potential confounders; a nested case-control study of demographic, clinical, histopathological, and genetic determinants was carried out using multiple logistic regression. Significant differences in TERT promoter mutation frequencies were noted in the subtypes (mixed vs. pure; 15/28, 54% vs. 11/48, 23%, respectively, P=0.0066). After adjusting for potential confounding, multivariate analyses indicated a three-fold increase in the odds of the TERT mutation for those with the mixed subtype compared with the pure subtype (P=0.04, adjusted odds ratio =3.32). No other significant associations were noted (sex/junctional component/Breslow depth/ulceration/mitoses/host response/RETp, BRAF status, and neurofibromin protein expression). Our findings, the largest to date investigating TERT promoter mutations in DM, support the hypothesis that the subtypes have distinct genetic drivers and underscore the relevance of telomere integrity in the etiopathogenesis of the mixed variant.

Expression of the p40 isoform of p63 has high specificity for cutaneous sarcomatoid squamous cell carcinoma.

Cutaneous spindle cell malignancies such as sarcomatoid squamous cell carcinoma (SCC), leiomyosarcoma, desmoplastic melanoma (DM) and atypical fibroxanthoma (AFX) may be morphologically indistinguishable, yet accurate diagnosis is important for appropriate clinical management. The distinction among these entities relies on immunohistochemical evaluation for epidermal, muscle or melanocytic differentiation. Epidermal differentiation markers include cytokeratins and p63. p63 is expressed as two distinct isoforms, ΔNp63 (p40) and TAp63. p40 positivity is highly specific for pulmonary SCC and head and neck sarcomatoid SCC. We examined the utility of p40 vs. p63 immunostaining in the differentiation of a variety of cutaneous spindle cell malignancies, including sarcomatoid SCC (n = 27), AFX (n = 34) and DM (n = 10). p40 was less sensitive than p63 for detecting sarcomatoid SCC (56% and 81%, respectively). p63 and p40 were comparably specific for sarcomatoid SCC relative to AFX, with only rare weak staining of tumor cells for p63 and/or p40 in a minority of AFX cases, including one case with approximately 10% of cells staining weakly for p40. All cases of DM were negative for p40 and p63. Our results support continued use of p63 for diagnosis of cutaneous sarcomatoid SCC because of greater sensitivity relative to p40.

Mélanome desmoplastique : une série de 23 cas dans trois centres des Bouches-du-Rhône

Desmoplastic melanoma (DM) is a rare form of melanoma, often with atypical and potentially misleading aspects that result in difficult and late diagnosis. Because of the high likelihood of local relapse, practitioners must have a good knowledge of such tumours. A retrospective study of the activities of 3 centres in the Bouches-du-Rhône region between 1998 and 2010 enabled us to collate 23 cases of DM and analyse the clinical and histological features of the disease as well as patient survival. Fifteen of the 23 patients (65.2%) were male with a median age of 64.4 years. Mean Breslow thickness was 7.56 mm. The numbers of AJCC (American Joint Committee for Cancer) stages I, II, III, IV were respectively 4.1, 66.7, 20.8 and 4.1%. Thirteen patients presented relapse, with a mean time to onset of 21 months. The initial relapse involved the skin in 1 case, the lymph nodes in 2 cases, the organs in 5 cases, the organs and subcutaneous region in 1 case, the organs and lymph nodes in 2 cases, and the organs, lymph nodes and skin in 1 case. While DM presents a higher rate of local relapse than classical melanoma, this trend appears to subside in the case of thick DM, in which relapse also involves the lymph nodes and/or organs.

Desmoplastic nevus of chronically sun-damaged skin: an entity to be distinguished from desmoplastic melanoma.

Desmoplastic (sclerotic) nevus (DSN) can often be difficult to differentiate from desmoplastic melanoma (DM). This can be especially difficult when DSNs occur in a background of heavy solar elastosis. We have observed numerous examples of DSNs occurring in chronically sun-damaged (CSD) skin. In a subset of these cases, we have observed notable pleomorphism and nuclear atypia raising concern for the possibility of DM. In this study, we evaluated the clinical, histopathologic, and immunohistochemical findings in 23 cases of DSN occurring in CSD skin and compared them with 10 cases of DM. DSN on CSD skin is seen in adults (mean, 53.2 years) with a female predominance (70%) and upper (57%) and lower (17%) extremity anatomic locations. Most DSNs present as small flesh-colored macules or papules. Typical histologic features include symmetry, limited junctional growth, presence of a lentiginous component often with focal and limited pagetoid spread (extension across only a few rete ridges), and lack of deep extension. DSN and DM had a statistically significant difference in immunohistochemical staining for Melan-A and p75. Melan-A was positive in 18 of 20 DSNs and only 2 out of 10 DMs, whereas p75 was positive in all DMs (10/10) and was weakly positive in 11 of 20 DSN cases. We believe that our study offers some useful clinical, histologic, and immunohistochemical clues to help differentiate DSNs on CSD skin from DMs.

Clinical and Dermoscopic Characteristics of Desmoplastic Melanomas

To describe and analyze the clinical and dermoscopic characteristics of desmoplastic melanoma (DM) as a function of pathologic subtype and phenotypic traits. Retrospective case series. Eight high-risk dermatology clinics. Patients with DM confirmed by histopathologic analysis whose records included a high-quality dermoscopic image. Clinical, dermoscopic, and histopathologic features of DM. A total of 37 DM cases were identified. The majority of patients had fair skin, few nevi, and no history of melanoma. Lentigo maligna was the most frequent subtype of melanoma associated with DM. The most frequent clinical presentation of DM was a palpable and/or indurated lesion located on sun-exposed skin. Forty-three percent of cases were classified as pure DM, and 57% as mixed DM. Pure DM lesions were thicker than mixed DM lesions (4.10 vs 2.83 mm) (P = .22) and were less likely to have an associated epidermal non-DM component (63% vs 100%) (P = .004). Dermoscopically, DMs had at least 1 melanoma-specific structure, the most frequent being atypical vascular structures. Peppering was more frequently seen in pure DM (44% in pure DM vs 24% in mixed DM) (P = .29). In contrast, crystalline structures, polymorphous vessels, and vascular blush were more commonly seen in mixed DM. Though DM can be difficult to diagnose based on clinical morphologic characteristics alone, dermoscopy has proved to be a useful aid during the evaluation of clinically equivocal lesions or those lesions with a benign appearance. The most common dermoscopic clues observed in DMs included atypical vascular structures, peppering, and occasionally other melanoma-specific structures.

Desmoplastic melanoma: a diagnostic dilemma.

Desmoplastic melanoma (DM) is an uncommonly encountered type of melanoma. A pigmentation is frequently absent, although a lentigo or lentigomaligna-like discolouration, adjacent to the nodule, is not uncommon. Hence, the clinical impression at presentation may vary from those of basal cell or squamous cell carcinomas, dermatofibromas or sarcomas to cysts and indurated plaque-like lesions which resemble scars. Making a cinical diagnosis of this tumour is difficult and it may very often mislead the physician. The clinical appearance of DM may be highly variable and the diagnosis of the tumour is difficult. We are reporting a case of DM which was diagnosed histopathologically and confirmed by immunohistochemistry (IHC), for its rarity and unique presentation.

Oral desmoplastic melanoma mimicking inflammatory hyperplasia

Desmoplastic melanoma (DM) arising in the oral cavity is a rare neoplasm that may be confused with a variety of non-melanocytic benign or malignant lesions. To present a case of DM in the oral mucosa mimicking fibrous inflammatory hyperplasia, discusses the difficulties involved in the diagnosis and offers a literature review on the clinicopathologic and immunohistochemincal aspects of this neoplasm. A 62-year-old white male, smoker, was referred with a chief complaint of pain and swelling in the palate. The oral examination revealed multiple brown-to-black patches and a non-pigmented sessile nodule located on the mucosa of the hard palate. The clinical diagnosis of the pigmented lesions was either oral melanosis or melanoma. The nodular lesion was clinically diagnosed as fibrous inflammatory hyperplasia. Incisional biopsy was performed on the pigmented lesion and the microscopic sections revealed a melanotic macule. The nodular lesions histologically revealed an amelanotic desmoplastic melanoma. Reactive lesions close to a pigmented area should be investigated with great care.

Microarray Comparative Genomic Hybridization Detection of Copy Number Changes in Desmoplastic Melanoma and Malignant Peripheral Nerve Sheath Tumor

Desmoplastic melanoma (DM) and malignant peripheral nerve sheath tumor (MPNST) can appear morphologically and immunophenotypically similar. We attempted to determine whether microarray comparative genomic hybridization could detect copy number differences between them to aid in the diagnosis. S-100 immunohistochemistry was performed on 5 cases of DM and 9 cases of MPNST using formalin-fixed paraffin-embedded specimens. Genomic DNA was extracted from microdissected cells. Whole genome amplification was performed on 5 of 5 DMs and 6 of 9 MPNST cases. A multiplex polymerase chain reaction assay was used to determine the quality of the DNA samples, which were run on the Spectral Chip 2600 bacterial artificial chromosome array platform. DM showed gains involving chromosomes 1p, 2p, 9q, 13q, 14q, and 20q and losses involving chromosomes 5p, 11p, 12q, 15q, and 18q. Several cancer-associated genes were involved, including gain of BCL2L1, ARTN, AMPK, NRAS, and CCNA1 and loss of IGF2, CDKN1C, PAX6, WT1, TRAF6, MAPK8IP1, and IMP3. MPNST had gains involving chromosomes 1p, 2q, and 19p and loss of chromosome 21q. Gains of MUM1, APC2, MAP2K2, JMJD2B, SP110, PTMA, GPI, and CDKN2D were detected. DM and MPNST have chromosomal alterations detected by array comparative genomic hybridization that might be useful in distinguishing these 2 tumors, although further studies with a larger sample size will be needed to test this.

Potentially Useful Markers for Desmoplastic Melanoma: An Analysis of KBA.62, p-AKT, and Ezrin

Desmoplastic melanoma (DM) represents only a small portion of newly diagnosed melanoma cases but can be a significant diagnostic challenge for dermatopathologists. Immunohistochemical stains are often useful to confirm the diagnosis; however, DM is notorious for not expressing most of the melanocytic markers other than S100. Recent studies have suggested several new markers, which may be promising in the diagnosis of DM. KBA.62 is a relatively new antimelanoma monoclonal antibody, which has not been well characterized in DM. Ezrin and p-Akt are additional markers, which have been shown to be involved in cell survival and proliferation. We collected 12 cases of DM and 18 cases of other lesions that could be included in the differential diagnosis. The H&E sections were reviewed, and immunohistochemical stains for KBA.62, p-AKT, and Ezrin were performed. Seventy-five percent of the DM cases (9 of 12) demonstrated positive staining (>5% of tumor cells staining) with KBA.62, with an average of 39% of cells staining. One hundred percent of the DM cases (12 of 12) demonstrated positive staining with Ezrin, with an average of 49% of tumor cells staining. Seventy-five percent of the DM cases (9 of 12) demonstrated positive staining with p-Akt, with an average of 49% of cells staining. KBA.62 and Ezrin demonstrated statistically significant increased staining of DM cases compared with the other lesions (P = 0.05 and P = 0.007, respectively), although it was not useful in distinguishing DM versus malignant peripheral nerve sheath tumor, whereas p-Akt showed no significant differences in staining between DM and the other cases. These findings suggest that KBA.62 may be a useful marker in confirming the diagnosis of DM.

Distinguishing neurofibroma from desmoplastic melanoma: the value of the CD34 fingerprint

We have observed 'fingerprint' immunopositivity in association with perineurioma and neurofibroma. A fingerprint consists of delicate, elongated areas of positive labeling that fall between collagen bundles, thereby creating a whorled configuration that is reminiscent of a human fingerprint. At present, the differential diagnosis between early desmoplastic melanoma and neurofibroma remains challenging in a subset of cases because of overlapping histopathological and immunohistochemical features. To assess whether fingerprint CD34 reactivity could be contributory in this context, we stained 50 desmoplastic melanomas and 50 neurofibromas with CD34. Fingerprint CD34 labeling was present in greater than 30% of the proliferation in 96% (n = 48) of neurofibromas and in only 4% (n = 2) of desmoplastic melanomas. Over two-thirds of the neurofibromas exhibited a CD34 fingerprint involving more than 60% of their surface area. In the two cases of desmoplastic melanoma that showed CD34 fingerprint positivity, the staining was patchy and involved less than 60% of the tumor. In partially staining neurofibromas, areas without a CD34 fingerprint tended to occur in central lobular areas. We conclude that CD34 fingerprint immunoreactivity is useful in distinguishing neurofibroma from early desmoplastic melanoma, especially if the fingerprint involves more than 60% of a tumor's cross-sectional area.

P75 nerve growth factor receptor staining is superior to S100 in identifying spindle cell and desmoplastic melanoma

Spindle cell melanoma (SCM) including desmoplastic melanoma (DM) is a rare variant of malignant melanoma that may present diagnostic difficulties particularly when staining with S100 is negative, weak, focal, or a combination of these. Conventional melanocytic markers in SCM are usually negative. We sought to compare the staining of p75 nerve growth factor receptor (NGF-R) and S100 in SCMs. We evaluated the staining of p75 NGF-R and S100 in 13 cases of SCMs: 3 SCMs without desmoplasia, 5 pure DMs, and 5 combined DMs with a conventional component. Staining with p75 NGF-R was positive in 13 of 13 (100%) cases of SCMs. In 3 cases the intensity of staining and the percentage of cells staining with this marker were greater than those with S100. One case of SCM was negative for S100 but demonstrated strong expression of p75 NGF-R. One case was focally and weakly positive with S100 but expressed strong positive staining with p75 NGF-R. Absence of staining with p75 NGF-R was noted in the conventional round cell component of two of 5 (40%) combined DMs whereas the same areas were strongly positive for human melanoma black (HMB)-45 and Melan-A. In 5 of 5 (100%) cases of combined DMs the desmoplastic component stained positive with p75 NGF-R, demonstrating an inverse relationship with the staining of conventional melanocytic markers. Small study size was a limitation. p75 NGF-R exhibits superior staining characteristics and greater sensitivity in identifying SCM and DMs than S100. P75 NGF-R may be a useful diagnostic and ancillary stain in addition to S100.

Subclassification of desmoplastic melanoma: pure and mixed variants have significantly different capacities for lymph node metastasis

There is disagreement about the behavior and optimal management of desmoplastic melanoma (DM), particularly regarding the incidence of lymph node (LN) involvement. Recently, investigators have noted the frequently heterogeneous histologic composition of DM and have found significant differences between pure desmoplastic melanoma (PDM) (>or=90% comprised of histologically typical DM) and mixed desmoplastic melanoma (MDM) [>or=10% DM and >10% conventional melanoma (CM)]. We reviewed 87 cases of DM comparing the histologic and clinical features of PDM (n = 44) to MDM (n = 43). At surgical staging, there were LN metastases in 5 of 23 (22%) MDM patients, whereas all 17 PDM patients had negative LN biopsies (0%) (p = 0.04). PDM was less often clinically pigmented (36% vs. 67%) and had a lower mean mitotic index (1.3 vs. 3.0). There are differences between PDM and MDM, the most important of which is the incidence of LN involvement. Our findings support the clinical utility of classifying DM into pure and mixed subtypes because the negligible rate of nodal involvement in PDM does not support the routine performance of sentinel LN biopsy in this subgroup of melanoma patients. In contrast, the incidence of LN involvement in MDM is comparable to that of CM.