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Tebentafusp is a bispecific protein that recently underwent FDA approval for the treatment of metastatic uveal melanoma that functions by redirecting cytotoxic T cells to glycoprotein-100, a protein highly expressed in melanoma. Although clinical trials have demonstrated that rashes are common in the first few days of treatment, little is known about skin reactions that develop later in the treatment course. Herein, we describe a type IV hypersensitivity reaction and vitiligo-like depigmentation that developed six weeks into treatment and discuss the possible mechanisms underlying these reactions. The type IV hypersensitivity reaction resolved without intervention within seven weeks of onset, suggesting that tebentafusp can be safely continued in select patients who develop this cutaneous reaction.

Spontaneous hair repigmentation of physiologically white or gray hair is a rare occurrence that may be associated with melanoma in elderly individuals. We present the first case of this phenomenon in a man. A gray-haired, 80-year-old man presented to dermatology clinic with a 3-cm lock of black hair on his vertex scalp that developed over 1 year. Punch biopsies showed an increase in junctional dendritic melanocytes with rare pagetoid cells and extension along the follicular outer root sheath epithelium and interfollicular epidermis, associated with prominent dendritic melanocytic hyperplasia and pigment-containing melanocytes within the hair bulbs. Although the findings on the biopsies were not diagnostic of melanoma in situ, an irregular interfollicular distribution of melanocytes was concerning for an adjacent atypical process. A complete excision was performed and revealed melanoma in situ, lentigo maligna type. Rare reports describe spontaneous hair repigmentation as a harbinger of lentigo maligna in women. Repigmentation can occur in the setting of proliferation of malignant pigment-producing melanocytes or by paracrine stimulation of benign bulbar melanocytes through receptor tyrosine kinase KIT activation. Presence of prominent dendritic melanocytic hyperplasia and pigment-containing melanocytes within the hair bulbs in our patient's biopsies was suggestive of paracrine or physiologic stimulation of bulbar melanocytes. Given the importance of early melanoma detection and the low visibility of the scalp, this report raises awareness of an extraordinary presentation of lentigo maligna and exemplifies the importance of close clinicopathologic correlation to ensure optimal clinical management and patient outcome.

Interdigitating dendritic cell sarcoma (IDS) is a rare form of hematologic malignancy associated with an aggressive clinical course. Only 4 prior cases have been described as originating in the skin. We encountered two male patients ages 47 and 61years of age who presented with solitary cutaneous neoplasms diagnosed as IDS. Histologic exam showed a coalescing nested and multinodular proliferation of large pleomorphic epithelioid cells. In one case an initial diagnosis of melanoma was rendered. A recurrence 8months later was then interpreted as a primary cutaneous IDS. This patient died of widespread metastatic disease within 2years from his initial surgery. The other patient has recently undergone wide excision and radiation without any recurrence or metastatic disease during this short follow up time period. Both patients had a tumor exhibiting the same phenotypic profile comprising leukocyte common antigen, SOX10, S100, CD68, and CD163 positivity. In reviewing the 4 other reported cases, there is a similar older male predominance (mean age of 58years) although women affected were significantly younger (mean age of 28years); there was a predilection for the proximal extremities and the face. Patients treated with excision only developed recurrent disease with one patient subsequently dying of metastatic disease. Primary cutaneous IDS is a highly aggressive hematologic malignancy that has many overlapping features with poorly differentiated epithelioid and spindle cell melanoma including SOX10 staining. An aggressive treatment protocol at the beginning could optimize patient survival., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: FISH has recently emerged as a technique to better assess the malignant potential of histologically ambiguous melanocytic lesions. However, the usefulness of FISH has not been conclusively established. The purpose of this study was to further explore the diagnostic value of FISH in distinguishing the borderline melanocytic tumor (BMT) from melanoma., Method: 73 cases with BMT were analyzed retrospectively from a dermatopathology database between 2010-2015. FISH studies were conducted in each case using probes targeting 5 loci including CCND1 on 11q13, RREB1 on 6p25, MYB on 6q23, CDKN2A on 9p21, and CEP 6 control probe for chromosome 6., Results: The study was composed of 50 females and 23 males with an age range of 1-73 and a mean age of 35years. Of the 6 cases in the superficial atypical Spitz tumor (AST) category, 2 had indeterminate results due to polyploidy. In the conventional atypical Spitz tumor cases, FISH was positive in 3 of 15 cases. Of the 27 cases in the borderline nevoid tumor (BNM) category, 3 showed positive FISH and 3 were equivocal due to the possibility of polyploidy. 3 of 13 cases of the borderline tumor of deep penetrating nevus variant (B-DPN) were positive for FISH. Neither of the 2 pigmented epithelioid melanocytoma (PEM) cases had positive FISH result. Of the 4 cases in the superficial atypical dermoepidermal nevomelanocytic proliferation group, only 1 met the FISH diagnostic criteria for melanoma. None of the 6 borderline tumors with overlapping features met FISH criteria diagnostic of melanoma. Clinical follow up was available on 55 patients. None of the patients had recurrence nor died of the disease. Lymph node biopsy was performed on five patients without evidence of metastasis., Conclusion: Despite the benefits of FISH, it is limited by the fact that melanomas are not genetically identical whereby certain genetic abnormalities are only seen in specific subtypes. Additionally, FISH only targets specific chromosomes resulting in limitations in sensitivity and specificity. Although FISH has proven to be highly sensitive and specific in distinguishing unequivocally benign from malignant lesions, in cases of histopathological ambiguity, these parameters cannot be assessed with great confidence because the histopathological diagnosis (gold standard) is not without uncertainty. The 4-probe set (excluding 9p21) consistently showed chromosomal aberrations throughout all groups, but only 10 of the 73 total cases (13%) met the diagnostic criteria for melanoma. Moreover, it would be wise to establish new cytogenetic reference values that incorporate these borderline lesions in an effort to better assess the possibility of malignant behavior and or define a cytogenetic profile supportive of its categorization as an indeterminate proliferation. Polyploidy is another inherent limitation, which leads to false positives due to the absolute signal counts incorrectly reflecting relative imbalances in the tumor genome., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Deep penetrating nevi (DPN) are a relatively uncommon subtype of melanocytic nevi. A small subset of these lesions exhibit atypical features (cytologic and architectural atypia, mitotic activity) seen in melanoma. These lesions we term the deep penetrating nevus-like borderline tumor. Unequivocal melanomas can show overlapping morphologic features of DPN, which have been termed plexiform melanomas., Patients and Methods: 40 cases of DPN-like borderline tumor were identified along with 6 cases of plexiform melanoma. Clinical follow up was obtained, along with cytogenetic analysis in the form of fluorescent in situ hybridization (FISH) and/or comparative genomic hybridization (CGH)., Results: The DPN-like borderline tumor cases included 24 females and 16 males. Of sentinel lymph node biopsies performed, 1/3 of cases showed lymph node involvement. All patients where an aggressive clinical approach was adopted remain free of disease. All 6 DPN-like borderline tumor cases tested by CGH showed normal cytogenetics, as did 7 of 9 cases tested by FISH. Of the plexiform melanomas, 4/6 patients died of disease. In 3 cases there was morphologic progression from a DPN-like borderline tumor to overt melanoma. In one case of progression, cytogenetics was normal in the DPN-like borderline tumor and then abnormal in the progressed melanoma., Conclusion: DPN-like borderline tumors are melanocytic tumors associated with a high incidence of regional lymph node disease and exhibiting the potential for melanoma progression despite a normal cytogenetic profile. Patients with these lesions should be aggressively managed, with at least complete re-excision and consideration of sentinel node biopsy, regardless of cytogenetic data.

A 41-year-old pregnant African-American woman noticed rapid growth of her cesarean delivery skin scar beginning at 14-week gestation. Skin biopsy, which was performed at 31 weeks, revealed poorly differentiated cutaneous melanoma. At 34 weeks, she underwent repeat cesarean delivery with tumor excision, pelvic lymphadenectomy and abdominal wall reconstruction. Locally advanced disease and anatomical limitations prevented attainment of negative surgical margins. Despite adjuvant chemotherapy and radiation, she died 1 year after diagnosis. Deferring biopsy of a suspicious skin lesion during pregnancy may have delayed the diagnosis of melanoma in this case and possibly affected the long-term outcome.

Objective: To investigate the usefulness of a novel marker for melanocytic proliferations., Design: Using a novel monoclonal antibody against soluble adenylyl cyclase (sAC), various benign and malignant melanocytic proliferations were immunostained., Setting: Weill Medical College of Cornell University dermatopathology laboratory., Main Outcome Measures: The results were qualitative, not quantifiable., Results: The sAC immunostaining produced distinctive patterns that paralleled melanomagenesis. At one pole of the spectrum were benign nevi, including atypical nevi of special sites and recurrent nevi showing a distinct pattern of dotlike Golgi staining, while at the opposite pole was melanoma, in which many cells demonstrated an intense pannuclear expression pattern, often accompanied by loss of the Golgi expression pattern. Melanomas of lentigo maligna and acral lentiginous subtypes exhibited the most striking pannuclear expression, while nodular melanomas showed the least, although with supervening enhanced diffuse cytoplasmic expression. Loss of the Golgi expression pattern was a feature of malignant melanoma., Conclusion: The sAC expression pattern is complex but seems discriminatory, with distinctive and variable staining patterns according to the nature of the lesion biopsied.

Background: Expression of microRNAs (miRs) has been shown to be altered in many solid tumours and is being explored in melanoma. The malignant potential of some melanocytic lesions is difficult to predict. We hypothesised that characterisation of miR expression in borderline melanocytic proliferations would lead to the identification of a molecular profile that could be used with known prognostic factors to differentiate lesions with high malignant potential., Methods: The miR expression profile of melanocytic lesions (benign naevi, malignant melanoma and borderline melanocytic tumours) was evaluated by real-time PCR., Results: PCR analysis revealed primary cutaneous melanomas had an 8.6-fold overexpression of miR-21 and a 7.5-fold overexpression of miR-155 compared with benign naevi (P<0.0001). In situ hybridisation confirmed these results. miR-21 and miR-155 were significantly overexpressed within borderline lesions (P=0.0011 and P=0.0048, respectively). When borderline lesions were categorised by mitotic activity and Breslow thickness, miR-21 was associated with mitotic activity and miR-155 was associated with thickness (P<0.025). Among 14 patients with borderline lesions who underwent sentinel lymph node biopsy (SLNB), positive SLNB was associated with increased miR-21 and miR-155 in the primary lesion compared with lesions with a negative SLNB., Conclusion: MicroRNA expression profiles can be used to characterise atypical melanocytic lesions.

Background: The borderline melanocytic tumor (BMT) is a morphologically and biologically indeterminate melanocytic proliferation manifesting worrisome architectural features and cytologic atypia exceeding that encountered in melanocytic nevi yet insufficient to warrant designation as melanoma. The criteria that define the BMT are not well defined nor is the concept widely recognized., Objective: The purpose of this study is to provide a practical framework for the approach to the dermal BMT., Methods: Thirty-two patients with BMTs extending into the reticular dermis and at a depth of 0.75 mm or more underwent local excision and sentinel lymph node biopsy between 2000 and 2006. Four categories of BMT were recognized: (1) nevoid BMT (BNM); (2) the atypical Spitz tumor (AST); (3) pigmented epithelioid melanocytoma (PEM); and (4) BMT arising in a deep penetrating nevus (B-DPN)., Results: Four patients were in the BNM category (male/female ratio [M:F] = 1:3; mean age = 27 years, range = 15-36), 14 in the AST category (M:F = 7:7; mean age = 20.9, range = 3-58), 7 in the PEM category (M:F = 4:3; mean age = 23.5, range = 3-39), and 7 in the B-DPN category (M:F = 5:2; mean age = 22.3, range = 14-36). The percentages of patients with positive sentinel nodes in each category were 25% (1/4), 35% (5/14), 14% (1/7), and 57% (4/7), respectively. The average time of follow-up was approximately 4.2 years. One patient, a 36-year-old man, died of disease, while the others are alive and well. In the one death attributable to widespread metastatic disease, the lesion was initially interpreted as a deep penetrating nevus; however, retrospective review revealed features compatible with a B-DPN; the review was prompted by a recurrence that was morphologically compatible with a Clark level V malignant melanoma, reflecting clinical and morphologic progression., Limitations: The mean follow-up was less than 5 years. Molecular studies to further explore the biologic commonality with melanoma were not performed., Conclusion: The dermal variant of BMT is a tumor of younger adults and children that can be associated with lymph node disease and a potential for morphologic and biologic progression when inadequately treated., (Copyright 2009 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)

Spitzoid lesions are diagnostically problematic because of a deceptive morphology and indeterminate behavior. The most problematic are atypical Spitz tumors whereby distinction from melanoma may be difficult. We have recognized a melanocytic lesion with a reproducible histomorphology, demonstrating characteristic demographic features, namely a predilection to involve younger female patients and common occurrence on the thigh. We have designated this lesion as the superficial atypical Spitz tumor and have encountered 27 cases. We believe that these lesions overlap histomorphologically with higher-grade dysplastic nevi and de novo intraepidermal epithelioid melanocytic dysplasia. We identified 19 additional cases that appear to represent transition into malignant melanoma of superficial spreading type arising in a background of the superficial atypical Spitz tumor. A limitation is that complete medical histories were not obtained for all patients. In conclusion, there exists a distinct subset of Spitz tumors that we designate as the superficial atypical Spitz tumor in which there is inherent dysplasia including lesions that evolve into melanoma of superficial spreading type.

A variety of clinical and histological presentations can accompany the evolution of malignant melanoma. Unusual cytological variants of malignant melanoma include balloon cell, signet ring cell, myxoid and other metaplastic changes. With the exception of a case of pemphigus-like changes associated with malignant melanoma in paraneoplastic pemphigus, acantholysis is not a common histopathological feature of malignant melanoma. We present two unique cases of malignant melanoma with varying degrees of extensive melanocytic discohesion in an acantholytic pattern mimicking pemphigus vulgaris, further referred to in this article as 'discohesive melanoma'. Routine direct immunofluorescence studies for pemphigus-related antibodies (IgG and C3) were negative. In one case, indirect immunofluorescence for desmoglein autoantibodies characteristic of pemphigus were negative, although positive antibodies to desmoglein 1 was detected using immunosorbent assay. The differential diagnoses and pitfalls in recognition of this unusual presentation of malignant melanoma along with possible pathogenetic mechanisms are discussed.

Since the 1960s, the clinical characteristics of melanoma, its histopathology and its biological basis have been the subject of intense study at pigmented lesion clinics in North America, Europe, and Australia. More recently, the immense database of the Melanoma Committee of the American Joint Committee on Cancer (AJCC) has been exploited through complex mathematical models to measure the impact of various histologic features of primary melanomas and of sentinel lymph node deposits and to correlate these parameters with patient survival. The wealth of modern information available to pathologists and clinicians has become of vital interest to the prognostication of the individual patient with melanoma. The purpose of this review is to bring to the attention of anatomic pathologists the essential characteristics of the pathology report for primary cutaneous melanoma in the modern era.

A potential diagnostic pitfall in the histologic assessment of melanoma is the inability to recognize unusual melanoma variants. Of these, the more treacherous examples include the desmoplastic melanoma, the nevoid melanoma, the so-called 'minimal-deviation melanoma,' melanoma with prominent pigment synthesis or 'animal-type melanoma,' and the malignant blue nevus. Also problematic are the unusual phenotypic profiles seen in vertical growth phase melanomas; these include those tumors whose morphological peculiarities mimic cancers of nonmelanocytic lineage and those melanomas that express aberrant antigenic profiles not commonly associated with a melanocytic histogenesis. Metaplastic change in melanoma, balloon cell melanoma, signet-ring cell melanoma, myxoid melanoma, small cell melanoma and rhabdoid melanoma all have the potential to mimic metastatic and primary neoplasms of different lineage derivations. Abnormal immunohistochemical expression of CD 34, cytokeratins, epithelial membrane antigen, and smooth muscle markers as well as the deficient expression of S100 protein and melanocyte lineage-specific markers such as GP100 protein (ie HMB-45 antibody) and A103 (ie Melan-A) also present confusing diagnostic challenges. In this review, we will discuss in some detail certain of these novel clinicopathologic types of melanoma, as well as the abnormal phenotypic expressions seen in vertical growth phase melanoma.

Background: The histological diagnosis of malignant melanoma can be challenging. Immunohistochemical techniques may define a critical role in certain cases, specifically in establishing a primary diagnosis of melanoma. CD34 is a hemopoietic stem cell antigen expressed in bone marrow and endothelial cells, and may also be expressed in vascular and spindle cell tumors; it is generally negative in malignant melanoma., Case Report: An 83-year-old white female presented with a 3-4 mm area on her right upper back, which had been present for several years. Histologic sections showed a polypoid distortion by sheets and nodules of transformed amelanotic melanocytes lying in intimate apposition to an attenuated epidermis without a concomitant radial growth phase. Tumor cells were extensively S-100 and CD34 positive and showed focal immunoreactivity with melan-A and HMB-45., Discussions: We present a case of malignant melanoma of nodular subtype, which strongly expressed CD34. The spectrum of abnormal phenotypes in malignant melanoma is reviewed, and a possible explanation for the presence of CD34 is discussed. This case demonstrates the potential of malignant melanoma to express CD34, defining an infrequently recognized aberrant phenotype. Whether or not expression of this marker is associated with a more aggressive clinical course remains to be determined.

Background: Consideration of sentinel lymph node biopsy (SLNB) is recommended for thin melanomas with poor prognostic features; however, few metastases are identified. The purpose of this study was to assess the cost effectiveness of SLNB in this population., Methods: The prospective melanoma database was reviewed to identify patients with melanomas <1.2 mm thick who had undergone SLNB. Physician and hospital charges were collected from the appropriate billing department., Results: A total of 138 patients were identified over an 8-year period (1994-2002). Two patients with positive SLNs were identified (1.4%), one with a melanoma <1 mm thick. Patient charges for SLNB ranged from $10,096 to $15,223 US dollars, compared with $1000 to $1740 US dollars for wide excision as an outpatient. Using these charges, the cost to identify a single positive SLN would be between $696,600 and $1,051,100 US dollars. The cost for wide excision would be between $69,000 and $120,100 US dollars. Assuming that all patients with a positive SLN would die of melanoma, the cost per life saved would be $627,000 to $931,000 US dollars., Conclusions: The cost of performing SLNB in this population is great and only a small number will have disease identified that will alter treatment. These data call into question the appropriateness of SLNB for thin melanomas.

The precursors to melanoma are generally considered to be related to nevi of different types. Here we emphasize the dysplastic nevus, the congenital nevus, and lentigo maligna as specific lesions. The dysplastic nevus is discussed not only as a formal precursor but also as a marker of cutaneous melanoma. The clinical and histologic characteristics are outlined, as well as evidence of progression in dysplastic nevi. The congenital nevus is briefly reviewed and emphasis is placed upon clues to malignant degeneration. The concept of lentigo maligna as a precursor as distinct from an in situ phase is detailed.

Rare skin neoplasms in humans, comprising nodules of heavily melanized cells, mimic melanocytic neoplasms seen in horses and laboratory animals and thus are termed animal type melanomas. In part because of their rarity, behavior is unpredictable; many cases manifest a long indolent phase, and metastases are reportable. Over 6 years, the authors encountered nine skin and one lymph node biopsy specimens from six patients in whom light microscopy of formalin-fixed, paraffin-embedded tissue sections stained with hematoxylin and eosin showed melanocytic neoplasms with prominent pigment synthesis. Clinical follow-up was obtained by telephone contact with clinicians. There were three women, two men, and one boy, aged 9 to 85 years, whose lesions were described as blue-black nodules with irregular borders from 1.0 to 4.0 cm in size, located on the scalp, lower extremities, back, and sacrum. The dermatopathology comprised confluent dermal sheets of heavily melanized cells whose nuclei, where discernible, were large with irregularly thickened membranes, coarse chromatin, prominent, often spiculated nucleoli, and irregular parachromatinic clearing. Mitoses were infrequent. Four lesions had an epidermal component. One patient suffered metastases to regional lymph nodes, liver, and lungs with lethal effect, one experienced regional lymph node metastases but is still alive, one had local cutaneous metastases but was lost to follow-up, and one has a chest wall mass that has not yet been investigated. This rare dermal-based melanocytic neoplasm with prominent pigment synthesis, the animal type melanoma, has a biological behavior difficult to predict on morphological grounds. We advise complete excision with a 1.0- to 2.0-cm margin of normal skin and clinical investigation for regional or distant metastases.