Desmoplastic malignant melanoma: a clinicopathological study of 25 cases

Cellular Schwannoma Mimicking a Nodular Melanoma on the Sole of the Foot, an Avoidable Diagnostic Pitfall

ABSTRACT

We report a rare case of cellular schwannoma (CS) manifesting as an ulcerated nodular lesion, mimicking spindle cell melanoma on the sole of the foot. CS, a benign variant of schwannoma, typically occurs in deep soft tissues but can rarely present cutaneously. The diagnosis of CS heavily relies on histopathological examination and immunohistochemical staining for specific markers such as SOX10 and S100. In this case, initial clinical suspicion of nodular melanoma was confirmed on biopsy, which revealed a spindle cell neoplasm positive for SOX10 and negative for melanocytic markers. Misdiagnosis of nodular melanoma was averted through complete excision. CS diagnosis demands careful consideration due to its resemblance to other spindle cell neoplasms, especially melanoma. Meticulous histopathological evaluation and immunostaining are important to differentiate CS from similar lesions, ensuring accurate diagnosis and appropriate management. This report contributes valuable insights into the diagnostic challenges and management of CS, particularly in unusual cutaneous presentations.

Paranasal sinus angiosarcoma with facial paralysis as a novel manifestation: a case report and literature review

BACKGROUND

Paranasal sinus angiosarcoma is an uncommon malignancy, with only a few reported cases worldwide. Although it exhibits multiple symptoms, facial paralysis has not been previously documented as a noticeable presentation.

CASE PRESENTATION

In this case, we report a 40-year-old male who presented with facial numbness and pain for one month, weakness of his facial muscles for 15 days, and recurrent right epistaxis for 1 year. He had a history of nasal inflammatory polyps with chronic sinusitis. Computed tomography and magnetic resonance imaging showed space-occupying lesions in the right nasal cavity and maxillary sinus, with bone destruction occurring in the sinus wall and turbinate. This patient then underwent endoscopic surgery. According to the histopathological and immunohistochemical results, he was eventually diagnosed with paranasal sinus angiosarcoma in April 2021. To date, this patient has not initiated any radiotherapy or chemotherapy and has survived with lymphatic metastasis for at least 3 years.

CONCLUSIONS

This manuscript suggests that paranasal sinus angiosarcoma can present with facial paralysis. Moreover, pathological and immunohistochemical tests are still vital for diagnosing paranasal sinus angiosarcoma and differential diagnosis. Additionally, regular follow-up is crucial for patients with paranasal sinus angiosarcoma, enabling monitoring of recurrence, metastasis, and recovery while contributing valuable clinical data to understanding this rare disease and associated research endeavours.

Local Recurrence Rates After Excision of Desmoplastic Melanoma: A Systematic Review and Meta-Analysis

BACKGROUND

Few prospective studies have evaluated local recurrence rates (LRR) after excision of desmoplastic melanoma (DM); however, several retrospective studies have reported high LRR.

OBJECTIVE

To determine LRR after excision of DM and evaluate factors affecting LRR.

MATERIALS AND METHODS

Systematic review of the PubMed, Embase, and Web of Science databases was performed to identify studies reporting local recurrence after excision of DM with conventional wide local excision (WLE), Mohs micrographic surgery (MMS), or staged excision (SE). Meta-analysis was performed to calculate summary LRR and pooled risk ratios (RR).

RESULTS

Literature search identified 4 studies evaluating MMS or SE (total n = 61 DM). 53 studies assessed WLE ( n = 3,080) and were analyzed quantitatively. The overall LRR after WLE of DM was 21% (95% CI, 0.16-0.28; n = 2,308). Local recurrence rate was higher with positive/unknown histologic excision margins (49%, 95% CI, 0.25-0.74; n = 91) versus negative histologic margins (11%, 95% CI, 0.07-0.17; n = 1,075; [ p < .01]). Neurotropism was also associated with increased LRR (RR, 1.79; 95% CI, 1.34-2.38, p < .01; n = 644).

CONCLUSION

DM has high LRR after WLE. Local recurrence risk was greatest with positive excision margins, indicating the importance of achieving negative microscopic margins. Greater study of MMS and SE for DM is required.

En Bloc Resection of Desmoplastic Neurotropic Melanoma with Perineural Invasion of the Intracranial Trigeminal and Intraparotid Facial Nerve: Case Report and Review of the Literature

Background Desmoplastic neurotropic melanoma (DNM) is a rare, highly malignant, and locally invasive form of cutaneous melanoma with a tendency for perineural invasion (PNI).

Methods We report a case of a 61-year-old man presenting with right-sided trigeminal neuralgia and progressive facial paresis due to the PNI of the intracranial trigeminal nerve and the intraparotid facial nerve from DNM. We also present a review of the literature with six cases of DNM with PNI of the intracranial trigeminal nerve identified.

Results The combined transtemporal-infratemporal fossa approach was performed to achieve total en bloc resection of the tumor mass followed by postoperative radiotherapy (PORT). After 24 months of follow-up, the patient remains disease free with no signs of recurrence on magnetic resonance imaging.

Conclusion We recommend the en bloc resection of the tumor mass followed by PORT for the management of DNM with PNI. A high index of suspicion for PNI as a cause of cranial neuropathies is essential for the early detection and treatment of patients with known melanoma.

Unusual Histopathological Patterns in Melanocytic Nevi With Some Previously Undescribed Patterns

Melanocytic nevi are one of the most common diagnoses in the daily practice of any dermatopathologist. Although in the vast majority of cases the final diagnosis is not difficult, there are certain rare and unusual morphologic variations that can elicit some diagnostic problems. Although some of these variations can be considered as mere morphologic oddities, others might lead to a differential diagnosis with melanoma, or with other tumors, including epithelial or neural tumors. In the current report, we review many of these morphologic variations and discuss the main differential diagnosis, when appropriate.

[Desmoplastic melanoma: a study of 23 cases at 3 centres in the Bouches-du-Rhône region]

BACKGROUND

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.

PATIENTS AND METHODS

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.

RESULTS

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.

DISCUSSION

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.

Infantile cellular schwannoma developing on the skin with atypical clinical features

Cellular schwannoma (CS) is a variety of schwannoma with a predominantly cellular growth, normally developing in middle-aged patients. In this report, we describe a 15-month-old infant with primary cutaneous CS on the knee. Because of its histologically malignant features, CS is sometimes overdiagnosed as a malignant nerve tumor. Therefore, awareness of this variant of schwannoma is important for dermatologists to avoid needless treatments for patients with CS.

Desmoplastic melanoma associated with an intraepidermal lentiginous lesion: case report and literature review

Desmoplastic melanoma tends to present as firm, amelanotic papules. Microscopically, it reveals a proliferation of fusiform cells in the dermis and variable collagen deposition, as well as intraepidermal melanocytic proliferation of lentiginous type in most cases. Biopsy in a 61-year-old white male patient, who had received a diagnosis of lentigo maligna on his face 10 years before, revealed a proliferation of dermal pigmented spindle cells and collagen deposition, reaching the deep reticular dermis, with a lentiginous component. Immunohistochemistry with S-100, Melan-A and WT1 showed positivity, but it was weak with HMB45. Desmoplastic melanoma associated with lentigo maligna was diagnosed. Several authors discuss whether desmoplastic melanoma represents a progression from the lentiginous component or arises "de novo". Desmoplastic melanoma represents a minority of cases of primary cutaneous melanoma (less than 4%). Identification of lentigo maligna indicates that desmoplastic melanoma should be carefully investigated.

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.

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.

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.

Primary cutaneous signet-ring cell melanoma with pseudoglandular features, spindle cells and oncocytoid changes

The authors report a 69-year-old man with a primary nodular malignant melanoma on the shoulder showing unusual histological features. It mostly consisted of markedly neoplastic melanocytes, which exhibited abundant clear cytoplasm compressing the nuclei to the periphery, resulting in a signet-ring appearance. In other areas of the melanoma, there were focally desmoplastic and pseudoglandular patterns and oncocytoid changes. Immunohistochemical studies showed that the tumor cells were uniformly positive only for S-100 protein and vimentin. Signet-ring cell melanoma is a rare histopathological variant of malignant melanoma with only a few described cases. To the best of our knowledge, this is the first case reporting a combination of the signet-ring cell melanoma with desmoplastic, pseudoglandular, and oncocytoid features.

Two cutaneous malignant melanomas at the same anatomic site: a case report with molecular evaluation

Patients who have had malignant melanoma are at an increased risk of developing a second primary melanoma compared with the general population risk of developing a first melanoma. Many of these second primary melanomas occur at a similar anatomic site as the first lesion. Determining whether a second lesion is indeed a separate primary vs. a metastasis or locoregional recurrence can be very difficult histologically. We report the case of a patient who developed a second melanoma, 2 years after the initial diagnosis, within 3 cm of the site of the original lesion. Because of distinct histomorphologic features, the second lesion was favored to be a separate primary. However, because of the nearly identical anatomic location, molecular testing for loss of heterozygosity and BRAF mutation was performed to help further make this distinction. The first lesion was found to have loss of heterozygosity and a BRAF mutation that were not present in the second lesion. While these tests cannot elucidate the true molecular origin of these lesions, they provide a useful clinical tool to assess whether a second lesion should be treated as a recurrence or as a separate lesion with unique biologic potential.

[Hypopigmented melanocytic tumors with spindle cells. A review]

Hypopigmented and achromatic melanocytic tumors with spindle cells represent a diagnostic challenge. Spindle cell nevi resemble neural tumors. Desmoplastic nevi imitate dermatofibromas. Hypopigmented and amelanotic blue nevi are variants of the common and cell-rich blue nevus with an enhanced difficulty to make a correct diagnosis due to the lack of pigment. All of the above benign melanocytic tumors with proliferations of hypopigmented spindle cells can more or less show aspects of desmoplastic melanoma. The differential diagnosis of these entities demands a combination of clinical and histological parameters as well as supporting immunostaining. Regarding desmoplastic melanoma, diagnoses frequently made are benign spindle cell neoplasms, scar or unspecific inflammatory condition. As the histological aspects can be so misleading, attention is necessary in order to make the correct diagnosis. Particular care must be taken to rule out desmoplastic melanoma in the case of spindle cell proliferations, a cicatricial or inflammatory process in the classical settings of face, volar skin, or mucous membranes. The spindle cell melanoma must be distinguished from other types of malignant spindle cell neoplasms, which can involve the skin. The differential diagnosis with such tumors is entrusted mainly to immunostaining.

Malignant melanoma in the 21st century, part 1: epidemiology, risk factors, screening, prevention, and diagnosis

Malignant melanoma is an aggressive, therapy-resistant malignancy of melanocytes. The incidence of melanoma has been steadily increasing worldwide, resulting in an increasing public health problem. Exposure to solar UV radiation, fair skin, dysplastic nevi syndrome, and a family history of melanoma are major risk factors for melanoma development. The interactions between genetic and environmental risk factors that promote melanomagenesis are currently the subject of ongoing research. Avoidance of UV radiation and surveillance of high-risk patients have the potential to reduce the population burden of melanoma. Biopsies of the primary tumor and sampling of draining lymph nodes are required for optimal diagnosis and staging. Several clinically relevant pathologic subtypes have been identified and need to be recognized. Therapy for early disease is predominantly surgical, with a minor benefit noted with the use of adjuvant therapy. Management of systemic melanoma is a challenge because of a paucity of active treatment modalities. In the first part of this 2-part review, we discuss epidemiology, risk factors, screening, prevention, and diagnosis of malignant melanoma. Part 2 (which will appear in the April 2007 issue) will review melanoma staging, prognosis, and treatment.

Desmoplastic melanoma: comparison of expression of differentiation antigens and cancer testis antigens

Desmoplastic melanoma is a diagnostic and therapeutic challenge. Immunohistochemical analysis with antibodies to melanoma antigens can complement morphologic evaluation. Although staining for S100 protein is generally positive, staining for other melanoma differentiation antigens, particularly gp100, Melan-A/MART1 and tyrosinase, is often negative despite being commonly positive in other melanoma types. A high clinical index of suspicion and better diagnostic techniques are essential as atypical features and incorrect diagnosis can lead to poor clinical outcomes. Antigens associated with melanoma, such as the melanocyte differentiation and cancer testis antigen, may become important targets for immune therapies. We characterized the patterns of antigen expression of desmoplastic melanoma from 32 patients, including gp100, Melan-A/MART-1, tyrosinase, MAGE-A1, MAGE-A4 and NY-ESO-1. Consistent positive staining with S100 was observed. Differentiation antigens were expressed more frequently than cancer testis antigens regardless of the histological subtype of desmoplastic melanoma. When present, cancer testis antigen expression correlated to positive staining with differentiation antigens. The diagnostic yield of desmoplastic melanoma did not increase with the addition of cancer testis antigen typing. Low levels of expression of cancer testis antigen may indicate that they are suboptimal targets for vaccine development in desmoplastic melanoma.

Differential expression of N-cadherin distinguishes a subset of metastasizing desmoplastic melanomas

Desmoplastic melanoma is a variant of spindle cell melanoma considered at low risk for distant metastases when compared with other forms of melanoma. The emphasis in the differential diagnosis of desmoplastic melanomas has been placed mostly in distinguishing it from scars and other benign spindle cell proliferations. In contrast, recognizing a subset of desmoplastic melanomas with higher metastatic potential has proven more difficult. We studied the expression of N-cadherin in 21 desmoplastic melanomas. The expression of N-cadherin was examined by immunohistochemistry using archive material and a mouse anti-N-cadherin monoclonal antibody previously shown to react in routinely processed paraffin-embedded tissues. Of 21 cases, N-cadherin was strongly positive in 10, only weakly or focally positive in 3, and negative in 8. Seven of 21 patients had distant metastases, and N-cadherin was strongly positive in 6 of those 7 cases. In contrast, only 1 of 11 patients within the group of N-cadherin-negative or weakly positive tumors had distant metastases. Our results show that strong N-cadherin expression in desmoplastic melanoma correlates with distant metastases and potentially more aggressive behavior. In contrast, desmoplastic melanomas with low metastatic potential are mostly negative or only focally positive for N-cadherin. The data suggest that N-cadherin may be a useful marker in recognizing a subset of desmoplastic melanoma with higher metastatic potential.

Assessment of the role of sentinel lymph node biopsy for primary cutaneous desmoplastic melanoma

BACKGROUND

The role of sentinel lymph node biopsy (SLNB) in the treatment of desmoplastic melanoma (DM) remains undefined. The purpose of this study was to evaluate the use of SLNB for DM.

METHODS

In all, 1850 patients with cutaneous melanoma underwent wide local excision and SLNB. Patients with DM were identified and stratified as 'pure' DM or 'mixed' DM (i.e., DM associated with at least one other common histologic subtype).

RESULTS

Of the 1850 patients, 65 (3.5%) had DM. Of these, 46 (70.8%) had pure DM and 19 (29.2%) had mixed DM. Patients with pure DM had a median tumor thickness of 3.5 mm and 6.5% were ulcerated. Compared with patients with pure DM, patients with either mixed DM or non-DM (n = 1785) had thinner primary tumors (median, 1.7 mm and 1.5 mm, respectively, each P < 0.001 vs. pure DM) that were more likely to be ulcerated (27.7% and 21.3%, respectively, each P < 0.05 vs. pure DM). Although the incidence of a positive SLN was similar in patients with mixed DM (15.8%) and non-DM (17.5%), patients with pure DM were less likely to have a positive SLN (2.2%) (each P < 0.01 vs. non-DM and mixed DM). At a median follow-up of 2.9 years, no patient with pure DM had recurred.

CONCLUSIONS

Despite having thicker primary tumors, patients with pure DM have a lower incidence of positive SLNs compared with patients with non-DM. Whereas the treatment approach for patients with mixed DM should be similar to that of other melanoma patients, patients with pure DM are unlikely to have metastatic disease in regional lymph nodes and SLNB may not be warranted.

Unusual histological variants of cutaneous malignant melanoma with some clinical and possible prognostic correlations

Malignant melanoma is known for the wide range of histological patterns it can assume mimicking other malignant tumors. We present a review of most of the unusual histological variants of cutaneous melanoma and describe their immunohistochemical features, associate clinical findings, and possible behavior related to the histological subtype. In addition, we propose their classification into four groups corresponding to the (1) architectural patterns; (2) cytologic features; (3) stromal changes; and (4) the possible association of these findings (i.e. architectural + cytologic features). Although most of these unusual variants have the same prognosis as conventional melanomas, with Breslow thickness and ulceration, being the most important predictor of survival in clinical stage I, some of them have a peculiar biologic behavior that the clinicians and the dermatopathologists should know in order to give melanoma patients all educational information available.

Biology of desmoplastic melanoma: a case-control comparison with other melanomas

PURPOSE

Previous studies have established that patients with desmoplastic melanoma (DM) have thicker primary tumors. Consequently, comparisons with other forms of melanoma have been strongly biased by differences in Breslow stage. This is the first case-matched control study comparing DM with other forms of melanoma.

PATIENTS AND METHODS

From a database of 3,202 melanoma patients treated at one institution, 89 patients with DM and 178 case-matched control patients (2:1) were identified by matching for tumor thickness, age, sex, and year of diagnosis. Clinical, pathologic, and outcome information was obtained from chart review.

RESULTS

Controls were matched successfully to patients for tumor thickness, age, sex, and year of diagnosis. Presentation with American Joint Committee on Cancer stage III or IV disease is less common in patients with DM compared to case-matched control patients (5% v 21%; P < .001). Re-excisions to obtain clear surgical margins are required more often in patients with DM compared to case-matched control patients (21% v 6%; P < .001). Risk of positive sentinel nodes is lower in patients with DM compared to case-matched control patients (8% v 34%; P = .013). Despite these differences, survival rates of patients with DM are the same as case-matched control patients.

CONCLUSION

Use of case-matched control patients matched for tumor thickness avoids biases introduced by the advanced Breslow stage of DMs. DMs are more locally aggressive than thickness-matched controls, and positive sentinel nodes are limited to patients with thick primary tumors. Importantly, patients with DM have survival rates similar to patients with other melanomas of similar thickness.

Desmoplastic malignant melanoma: a systematic review

BACKGROUND

Desmoplastic melanoma (DM) is an uncommonly encountered type of malignant melanoma. The clinical appearance of DM can be highly variable and thus, diagnosis of this tumour is difficult and very often may mislead the physician.

OBJECTIVES

To make a critical review of the contemporary literature on DM, to pool the data from published studies and to evaluate the clinical and morphological characteristics of this neoplasm.

METHODS

All studies or reports on DM including 10 or more participants with reported clinical and histological characteristics of the tumour were included.

RESULTS

In the 17 studies that met the inclusion criteria a total of 856 patients with DM was reported. There was a male predilection, with a male/female ratio of almost 2 : 1 (63% of the lesions were diagnosed in males). The head and neck were the most common sites of DM for both sexes (53.2%). The data confirmed that DM usually has an advanced Breslow thickness at the time of presentation. Histopathological diagnosis of DM is sometimes difficult and the absence of pigmentation is probably the major cause for failure to recognize DM histologically. The pooled data from included studies showed that the incidence of nodal metastasis is lower in patients with DM than in patients with other forms of cutaneous melanoma.

CONCLUSIONS

Prompt definitive surgical excision is the treatment of choice for DM. Improved knowledge of the clinical behaviour and histological features of DM is important for more effective management of patients with DM.

Cutaneous desmoplastic melanoma: reappraisal of morphologic heterogeneity and prognostic factors

Desmoplastic melanoma (DM) is a variant of melanoma, which may be confused with nonmelanocytic benign or malignant spindle cell proliferations. The histologic hallmark of DM is the presence of fusiform melanocytes dispersed in a prominent collagenous stroma. Phenotypic heterogeneity of DM is underrecognized. Desmoplasia may be prominent throughout the entire tumor ("pure" DM) or represent a portion of an otherwise nondesmoplastic melanoma ("combined" DM). We reviewed melanomas with desmoplasia from 92 patients seen at a single institution between 1980 and 2002. Fifty-five of the tumors were pure DM. Thirty-seven were classified as combined. Mean follow-up of patients was 46 months for those alive at the last follow-up. Univariate analysis of clinical and pathologic parameters revealed four significant variables for disease-free survival: Clark level (IV vs. V; P = 0.005), DM subtype (pure vs. combined; P = 0.01), tumor mitotic rate (<1, 1-4, >4 mitoses/mm; P = 0.01), and tumor thickness (<1 mm, 1-4 mm, >4 mm; P = 0.02). Only histologic subtype (P = 0.02) and Clark level (P = 0.05) were independently significant by Cox regression analysis. Our results indicate that distinguishing pure from combined forms of DM is clinically relevant for prognosis (pure forms being associated with longer disease-specific survival). Failure to make this distinction may account for conflicting reports in the literature on the biologic behavior and prognosis of DM.

Cutaneous desmoplastic melanoma

Desmoplastic melanoma (DM) is a fibrosing variant of spindle cell melanoma. It most often presents as an indurated lesion in chronically sun-damaged skin. Due to the lack of characteristic clinical features, early detection is uncommon. At the time of excision, the tumors usually extend into the reticular dermis or deeper. DM is prone to misdiagnosis. It may simulate histologically sclerosing melanocytic nevi as well as various benign and malignant nonmelanocytic lesions. There is significant morphologic variability among tumors classified as DM. Desmoplasia may be prominent throughout the entire tumor ("pure" DM) or represent a portion of an otherwise nondesmoplastic melanoma ("combined" DM). Some tumors show neuroma-like features with prominent nerve involvement, in which case the term "desmoplastic neurotropic melanoma" is used. Immunophenotypically, DMs are usually strongly and homogeneously positive for S-100 protein but are often negative or only focally positive for melanocyte differentiation antigens such as tyrosinase, gp100, Melan-A, and microphthalmia transcription factor. 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. Evidence is also emerging that for patients with thick melanomas, the presence of a paucicellular fibrosing tumor histology (pure DM) is a favorable prognostic factor for survival.

Desmoplastic melanoma: a diagnostic trap for the unwary

Desmoplastic melanoma (DM) is an uncommon type of spindle cell melanoma in which the malignant cells are separated by collagen fibres or fibrous stroma. DM is prone to misdiagnosis because of unfamiliarity with its often bland appearance and dissimilarity to other conventional types of melanoma. It displays variable cytological atypia, cellularity and stromal fibrosis and more often than not has an accompanying atypical junctional component. Neurotropism is a common associated feature (in at least 30% of cases) and when it occurs such tumours are termed 'desmoplastic neurotropic melanomas' (DNM). The neurotropism may be perineural or intraneural and often extends beyond the desmoplastic component. In addition, some DMs show evidence of neural differentiation ('neural transformation'). DM may also present as a recurrence or occasionally as a metastasis from other types of melanoma. A high index of suspicion and knowledge of its often subtle morphological appearance are necessary to avoid misdiagnosis.

Desmoplastic melanoma of the nail

Desmoplastic melanoma represents a variant of melanoma that is difficult to diagnose because 71% of patients have amelanotic skin lesions. In the acral region of the limbs, the clinical diagnosis is more difficult, especially in cases in which there are not clear, rapidly growing, pigmented nail streaks. Histopathological identification of desmoplastic melanoma is confusing because of the intense fibrous reaction in the dermis and minimal, atypical melanocytic proliferation at the dermal-epidermal junction. For these reasons, it is still misdiagnosed unfortunately as a variety of entities, including simple scar, fibrohistiocytic neoplasms, neural tumors, and superficial fibromatoses-with potentially devastating consequences. In equivocal cases, the use of immunohistochemistry (in particular S-100 and neuron-specific enolase) may be helpful in establishing the diagnosis. Because of the high local recurrence rate for desmoplastic melanoma of the finger, amputation is recommended in an effort to gain effective tumor control. Lymph node dissection may be reserved for patients with positive axillary nodes.

Desmoplastic neurotropic melanoma of the head and neck: the role of radiation therapy

BACKGROUND

Desmoplastic neurotropic melanoma (DNM) is an uncommon cutaneous melanoma variant with pronounced neurotropism. In contrast to ordinary melanomas, locoregional recurrences are common and distant metastasis are uncommon in patients with DNM. Local control with surgery and radiation therapy may assume a more important role in this variant of melanoma. We present a case of an unresectable skull base recurrence of DNM that was controlled using radiation therapy alone and review the literature.

METHODS

Case report with 36-month follow-up.

RESULTS

The patient is a 68-year-old with multiple recurrences of a DNM that originated on the forehead. After extensive surgery, including total parotidectomy and temporal bone resection, the patient had an unresectable recurrence of the skull base develop. This was treated with definitive radiation therapy, resulting in a complete response. The patient has had no evidence of recurrence at 3 years.

CONCLUSIONS

DNM is a locally aggressive type of melanoma with a high risk of local recurrence that can be radioresponsive. The incidence of distant metastasis is low, so aggressive treatment to control local disease is warranted. This may include surgery plus adjuvant radiation therapy or definitive radiotherapy for unresectable recurrences.

A case of cellular schwannoma of the skin presenting as a large ulcerated tumor on the ankle

Cellular schwannoma (CS) is a rare, benign, nerve sheath tumor. It is slowly growing and painless, and it shows a predilection for the paravertebral region of the mediastinum and the retroperitoneum. CS rarely occurs in the skin. It has more cellular and more atypical cytological features than ordinary schwannoma but follows a benign clinical course. The key histological feature is a distinct predominance of cellular Antoni A tissue. Herein we report a case of CS presenting as a 5 x 5 x 3 cm, ulcerated and protruding tumor on the left ankle and describe its indolent clinical course.

Psammomatous malignant melanoma arising in an intradermal naevus

AIMS

A wide variety of differentiation patterns may be found in malignant melanoma. Schwannian features are unusual, and mostly present in the desmoplastic variant. We report the first description of psammoma bodies in malignant melanoma.

METHODS AND RESULTS

A malignant melanoma arose in an intradermal naevus of the scalp in a 51-year-old woman, displaying focal neural-like features in the form of rosette-like pseudo-meissnerian alveolar nests, as well as numerous psammoma bodies grouped in a few areas. Tumour cell immunostaining for S100, HMB45, NKI-C3, and vimentin was detected. In addition, both malignant and benign melanocytic cells showed widespread MART-1 immunoreactivity. Differential diagnosis with psammomatous melanotic schwannoma, a feature of Carney's complex, is particularly emphasized, since dermal variants of this nerve sheath neoplasm have been described. In addition, its potential relationship with cutaneous malignant melanotic neurocristic tumour is discussed.

CONCLUSIONS

This is, to our knowledge, the first reported case of cutaneous malignant melanoma with psammoma bodies.

S100 expression in cutaneous scars: a potential diagnostic pitfall in the diagnosis of desmoplastic melanoma

AIMS

The histological distinction of desmoplastic melanoma from cutaneous scar tissue, particularly in the context of re-excision specimens or possible recurrence, may be very difficult. Immunostaining for S100 protein is often used to discriminate although there are little data on S100 expression in scar tissue. The aim of this study was to assess whether S100-positive cells are present in dermal scars and, if so, their extent, distribution and nature.

METHODS AND RESULTS

Twenty-two re-excision specimens of previously biopsied nonmelanocytic skin lesions were reviewed. Formalin-fixed paraffin-embedded sections containing dermal scars were stained by a standard ABC immunoperoxidase technique for S100 protein, CD1a and neurofilaments. The distribution and morphology of positive cells within the dermal scar tissue were documented. Cells expressing S100 protein were identified within the scars of 21 of the 22 cases. The number of S100-positive cells varied between cases but in four specimens was substantial. They displayed a variety of morphological appearances but the majority were spindle-shaped. A few showed mild cytological atypia. It is suggested that the majority represent Schwann cells with a minority of Langerhans cells and cells of uncertain lineage.

CONCLUSION

S100-positive cells, including spindle cells showing mild atypia, are found in cutaneous scars. S100 staining of re-excision specimens or putative recurrences of desmoplastic melanoma should be interpreted with caution.

Morphological and immunophenotypic variations in malignant melanoma

A variety of cytomorphological features, architectural patterns and stromal changes may be observed in malignant melanomas. Hence, melanomas may mimic carcinomas, sarcomas, benign stromal tumours, lymphomas, plasmacytomas and germ cell tumours. Melanomas may be composed of large pleomorphic cells, small cells, spindle cells and may contain clear, signet-ring, pseudolipoblastic, rhabdoid, plasmacytoid or balloon cells. Various inclusions and phagocytosed material may be present in their cytoplasm. Nuclei may show bi- or multi-nucleation, lobation, inclusions, grooving and angulation. Architectural variations include fasciculation, whorling, nesting, trabeculation, pseudoglandular/pseudopapillary/pseudofollicular, pseudorosetting and angiocentric patterns. Myxoid or desmoplastic changes and very rarely pseudoangiosarcomatous change, granulomatous inflammation or osteoclastic giant cell response may be seen in the stroma. The stromal blood vessels may exhibit a haemangiopericytomatous pattern, proliferation of glomeruloid blood vessels and perivascular hyalinization. Occasionally, differentiation to nonmelanocytic structures (Schwannian, fibro-/myofibroblastic, osteocartilaginous, smooth muscle, rhabdomyoblastic, ganglionic and ganglioneuroblastic) may be observed. Typically melanomas are S100 protein, NKIC3, HMB-45, Melan-A and tyrosinase positive but some melanomas may exhibit an aberrant immunophenotype and may express cytokeratins, desmin, smooth muscle actin, KP1 (CD68), CEA, EMA and VS38. Very rarely, neurofilament protein and GFAP positivity may be seen.

Comparison of S-100 versus hematoxylin and eosin staining for evaluating dermal invasion and peripheral margins by desmoplastic malignant melanoma

Desmoplastic malignant melanoma (DMM) is a rare and locally aggressive variant of malignant melanoma, which is difficult to diagnose clinically and microscopically. A retrospective study of 21 DMM were collected during 7 years, representing 1.7% of melanomas. By comparing S-100 and hematoxylin and eosin (H & E) staining in DMM, we sought to determine whether S-100 staining offered a more accurate means of assessing dermal and neural invasion, tumor thickness, and peripheral margins. Eleven cases were excluded because the tumor extended past the deep margin. Six cases that were stained with S-100 showed a greater tumor thickness than by H & E (difference of 0. 13 to 2.79 mm). In two cases, the tumor thickness was greater by using H & E than S-100, and there was no difference in the remaining two cases. Of the eight cases in which the peripheral margins were positive by S-100, neoplastic cells were only apparent at those margins in four cases when examined with H & E. The remaining two cases showed negative margins by both stains. Clinical follow-up was obtained from nine cases, and none had recurrence of melanoma. Particularly for hypocellular and amelanotic tumors, S-100 staining proved to be a valuable adjunct in determining the extent of the tumor at the peripheral margins.

Fine-needle aspiration cytology of desmoplastic malignant melanoma metastatic to the parotid gland: case report and review of the literature

We report a case of desmoplastic malignant melanoma metastatic to the parotid gland initially evaluated by fine-needle aspiration. The cytologic findings consisted of scattered spindle cells in a background of heterogeneous lymphoid cells. The spindle cells were scant and displayed mild cytologic atypia. In addition, rare stromal fragments were also present. Cytoplasmic pigment and intranuclear cytoplasmic inclusions were not seen. The initial impression was that of a reactive lymph node with fibrosis. In retrospect, rare spindle cells displayed moderate atypia. In addition, the stromal fragments were cellular and contained spindle cells with mild atypia. These cytologic findings along with a known history of malignant melanoma should provide clues to the correct diagnosis of desmoplastic malignant melanoma. Diagn. Cytopathol. 2000;22:97-100.

Actin-rich desmoplastic malignant melanoma: report of three cases

We report three cases of desmoplastic malignant melanoma (DMM) rich in smooth muscle actin. They occurred in two men (Cases 1 and 3) and in one woman (Case 2). Cases 1 and 2 were recurrent lesions from common melanomas excised, respectively, 3 and 1 years previously. In Case 3, DMM was associated with lentigo maligna at the time of presentation. Morphologically, DMMs were composed of spindle neoplastic cells organized in haphazardly orientated long fascicles separated by collagen bundles. Perineural invasion was present and mitotic activity was prominent in all cases. The neoplastic spindle cells were intensely positive with S100 protein and smooth muscle actin antisera and negative with HMB45 and Melan-A (Mart-1) antibodies. Double staining for smooth muscle actin and S100 protein revealed no definite coexpression of the two antigens. Follow-up was available for patients 1 and 2 who had local recurrences and are still alive. It is possible that actin rich elements differentiate toward mesenchymal elements, paralleling the phenotypic changes seen in sarcomatoid carcinomas. Therefore, multidirectional differentiation may explain the mesenchymal (sarcomatoid) differentiation of neoplastic melanocytes and may be responsible for the different biologic behavior of DMMs, which is closer to mesenchymal tumors than to conventional melanomas.

Recent developments in the pathology of melanocytic neoplasia

This article selectively discusses clinically relevant aspects of the pathology of cutaneous melanocytic neoplasms, from the literature of the past recent years. Topics include the changing role of immunohistochemistry in diagnosis, the controversies over dysplastic nevi, description of other specialized variants of melanocytic nevi, diagnosis of melanocytic neoplasms of acral skin, and melanoma occurring in childhood. Several variants of melanoma including desmoplastic and spindle-cell types, verrucous melanoma, epidermotropic melanoma, and melanoma of the female genitalia are reviewed. The issue of appropriate margins of resection for melanoma and the use of Mohs Micrographic surgery for this tumor are considered. Finally, a review of the sentinel node biopsy technique and of nodal nevi is presented.

Desmoplastic malignant melanoma: diagnosis of early clinical lesions

Desmoplastic malignant melanoma (DMM) is an uncommon but potentially devastating malignancy that can be cured with early recognition and surgery. DMM has clinical as well as histological features that may be subtle and overlooked, or misdiagnosed as other benign or malignant lesions that would require less aggressive therapy for cure. We have reviewed the preliminary clinical diagnoses and histological features of 18 cases of desmoplastic malignant melanoma, defined as either an inapparent lesion clinically, or a papule or small nodule less than 0.7 cm, which proved histologically to be DMM. Nine of 18 cases (50%) were clinically pigmented. Histologically, early lesions were characterized by superficial tumor fascicles, and random diffuse hypercellularity in the upper dermis identified as elongated hyperchromatic pleomorphic spindle cells with stromal myxoid change. Neuroidal melanocytic structures, invasion of adventitial dermis, islands of inflammation, and epidermal lentiginous melanocytic hyperplasia were often present. The most reliable and characteristic features of an early lesion of DMM are aggregates of lymphocytes, tumor cell cytological atypia, stromal myxoid change, and poor circumscription of the dermal infiltrate. DMM is a disease best treated by complete excision at the time of initial surgery, but is also a lesion easily missed or misdiagnosed in the early stages. Features of early DMM are identified and illustrated to enable early diagnosis and cure of these lesions.

Desmoplastic malignant melanoma on the buttock of an 18-year-old girl: differentiation from desmoplastic nevus

Melanocytic proliferation in young people may sometimes pose a diagnostic dilemma. This is particularly so when a desmoplastic component is present. Because the two main differential diagnoses, desmoplastic malignant melanoma and desmoplastic Spitz nevus, share some morphologic features, the diagnosis of desmoplastic malignant melanoma may be overlooked. Distinction between the two is important because they show completely different biological behavior. The age of patient, site of lesion, histologic findings of melanocytic atypia, neurotropism, mitosis, and maturation help to distinguish the two entities. We report a case of desmoplastic malignant melanoma occurring in the buttock of an 18-year-old Chinese girl. Histologically, it had typical features of desmoplastic malignant melanoma with junctional melanocytic atypia and prominent neurotropism. Clinical and histologic differences between desmoplastic malignant melanoma and desmoplastic Spitz nevus are reviewed. We conclude that although desmoplastic Spitz nevus occurs much more commonly in adolescents, desmoplastic malignant melanoma can occur in this age group and even in non-sunexposed skin. Microscopic findings remain the mainstay that guides the final diagnosis.

Recognition and management of high-risk cutaneous tumors

The majority of cutaneous malignancies can be treated by the military dermatologist in a clinical setting. Recognition of tumors at high risk for recurrence or metastasis is important for any dermatologist but especially list care. Providing optimal care includes knowledge about which patients should be medavacced to larger medical centers for advanced surgical and medical treatments.

De novo desmoplastic neurotropic melanoma of the lower lip: a neoplasm with ominous behavior

Desmoplastic neurotropic melanoma represents a rare histologic variant of malignant melanoma that is characterized by a proliferation of spindle cells in a densely collagenous stroma with pronounced neurotropism. A 60-year-old man appeared for evaluation of a mass in the lower lip. The labial mucosa was intact, and the lesion had been present for 2 months. The tumor was surgically removed, and after immunohistochemical and ultrastructural analysis it was diagnosed as desmoplastic neurotropic melanoma. The tumor recurred 6 months later, with involvement of the inferior alveolar nerve.