Histopathologic, genomic, transcriptomic, and functional characteristics of eight melanocytic tumors with BRAF fusions showing stronger MAPK pathway activation compared to BRAF V600E tumors.

BACKGROUND: Activating BRAF gene alterations are central to melanocytic tumor pathogenesis. A small, emerging subset of melanocytic tumors driven by BRAF fusions has distinct therapeutic implications and has been described to have Spitzoid morphology patterns. However, such morphological patterns do not encompass all cases, and little is known about the functional molecular events. MATERIALS AND METHODS: We conducted a retrospective search through our molecular archives to identify melanocytic tumors with BRAF fusions. We reviewed clinical, histopathological, and genomic features. We further explored transcriptomic and protein-level findings. RESULTS: Histopathologic patterns varied, with many cases without a distinctive pattern. We identified novel and diverse BRAF gene fusion partners. Differential transcriptomic analysis between low-risk BRAF fusion tumors and reference BRAF V600E tumors showed no differentially expressed genes. However, quantitatively stronger MAPK pathway activation of BRAF fusion tumors over BRAF V600E tumors was demonstrated by statistically significant stronger staining of p-ERK immunohistochemistry. Gene-specific RNA analysis shows comparable BRAF transcript levels between the two groups. DISCUSSION AND CONCLUSION: The quantitatively stronger activation of the MAPK pathway of BRAF fusion tumors, instead of qualitatively different transcriptomes, may account for the morphology difference from conventional BRAF V600E tumors. BRAF fusions likely act through dysregulated protein function rather than RNA upregulation related to the characteristics of the fusion partners.

Utility of sequencing for ATP6AP1 and ATP6AP2 to distinguish between atypical granular cell tumor with junctional component and melanoma.

BACKGROUND: Granular cell tumor (GCT) is a S100+ neoplasm with atypical and malignant variants. Similar to melanocytic neoplasms, the tumors make nests and can have junctional components raising a differential diagnosis of melanoma. Nevi and melanomas may also have granular cell cytoplasm. MelanA is useful in distinguishing melanocytic from granular cell lineage, but increasingly MelanA/SOX10 negative melanomas have been recognized by correlation with molecular methods. METHODS: We encountered several cases with morphologic overlap between melanoma and atypical GCT necessitating additional molecular workup. We sequenced two cases and searched our archive for similar cases of GCT with overlapping features of melanocytic lineage. RESULTS: In our two index cases, we excluded melanoma driver mutations and identified frameshift or premature stop codons in ATP6AP1/2 pathognomonic of granular cell lineage. Data retrieved from Cosmic identified 24 melanomas with missense single nucleotide variants (SNVs) in ATP6AP1 but no frameshift or premature stop codons. Twenty-one melanomas had missense SNVs in ATP6AP2. One melanoma had a premature stop codon in ATP6AP2, but this lesion also had a melanoma-associated driver mutation NRASQ61K. We found 1 of 23 additional cases of GCT in our archives with a junctional component and no additional cases with maturation. CONCLUSIONS: Atypical and malignant GCT can have histopathologic overlap with melanoma. Frameshift and premature stop codons in ATP6AP1/2 are specific for granular cell lineage, and capable of excluding melanoma, in the absence of known melanoma-associated driver mutations.

MAP2K1-mutated melanocytic tumors have reproducible histopathologic features and share similarities with melanocytic tumors with BRAF V600E mutations.

BACKGROUND: Melanocytic tumors driven by MAP2K1 in-frame deletions are among the most recently described class of melanocytic neoplasms. The reported range of diagnoses and associated genomic aberrations in these neoplasms is wide and includes melanomas, deep penetrating melanocytomas, and pigmented epithelioid melanocytoma. However, little is known about the characteristics of these tumors, especially in the absence of well-known second molecular "hits." Moreover, despite their frequent spitzoid cytomorphology, their potential categorization among the Spitz tumors is debatable. MATERIALS AND METHODS: We conducted a retrospective search through our molecular archives to identify sequenced melanocytic tumors with MAP2K1 in-frame deletions. We reviewed the clinical and histomorphological features of these tumors and compared them to similar neoplasms reported to date. In addition, we performed single-nucleotide polymorphism (SNP) array testing to identify structural chromosomal aberrations. RESULTS: Of 27 sequenced tumors, 6 (22%) showed a pathogenic MAP2K1 in-frame deletion (with or without insertion) and were included in this series. Five (83%) were females with lesions involving the upper limb. Histopathologically, all neoplasms were compounded with plaque-like or wedge-shaped silhouettes, spitzoid cytomorphology, and impaired cytologic maturation. All cases showed background actinic damage with sclerotic stroma replacing solar elastosis, variable pagetoid scatter, and occasional dermal mitotic figures (range 1-2/mm2 ). Five cases (83%) had a small component of nevic-looking melanocytes. Biologically, these tumors likely fall within the spectrum of unusual nevi. Five cases (83%) had a relatively high mutational burden and four (67%) showed an ultraviolet radiation signature. Four cases (67%) showed in-frame deletion involving the p.I103_K104del locus while two cases (33%) showed in-frame deletion involving the p.Q58_E62del locus. SNP array testing showed structural abnormalities ranging from 1 to 5 per case. Five of these cases showed a gain of chromosome 15 spanning the MAP2K1 gene locus. DISCUSSION AND CONCLUSION: Melanocytic tumors with MAP2K1 in-frame deletion could represent another spectrum of melanocytic tumors with close genotypic-phenotypic correlation. They are largely characterized by a spectrum that encompasses desmoplastic Spitz nevus as shown in our series and Spitz and Clark nevus as shown by others. Evolutionary, they share many similarities with tumors with BRAF V600E mutations, suggesting they are better classified along the conventional pathway rather than the Spitz pathway despite the frequent spitzoid morphology.

Detection of driver mutations in BRAF can aid in diagnosis and early treatment of dedifferentiated metastatic melanoma.

Dedifferentiated metastatic melanoma can pose a significant diagnostic challenge, especially if the history of primary melanoma is not known or is remote. BRAF and NRAS mutations are common melanoma driver mutations that are usually sequenced to evaluate for treatment targets. We evaluated whether BRAF and NRAS mutational testing could contribute to the diagnosis of dedifferentiated metastatic melanoma when immunostains are negative. Seven patients with melanoma who had an additional diagnosis of poorly differentiated sarcoma with negative melanocytic immunostains were tested for BRAF and NRAS mutations. Three patients showed identical BRAF mutations in the melanoma and the poorly differentiated sarcoma and hence were re-classified as metastatic dedifferentiated melanoma. In these three patients, there was an average delay of 7 months before appropriate testing, workup and treatment for metastatic melanoma was initiated. Two of these patients currently have stable metastatic disease and show sustained therapeutic response to melanoma-specific treatment including BRAF inhibitors. BRAF mutational analysis should therefore be considered in cases of poorly differentiated sarcoma, especially if there is a known history of melanoma or with unusual localization of disease. The administration of melanoma-specific treatments in such dedifferentiated cases can show therapeutic response, highlighting the importance of rendering accurate diagnoses on such cases.

Epithelial sheath neuroma: evidence supporting a hyperplastic etiology and epidermal origin.

An epithelial sheath neuroma (ESN) is a rare benign process of unknown pathogenesis, which is characterized histologically by multiple enlarged peripheral nerve fibers ensheathed by mature squamous epithelium. The histologic features can elicit concern for carcinomatous perineural invasion. The process is limited to the superficial dermis and is surrounded by a loose myxoid stroma, lymphocytic infiltrate and sometimes prominent infundibular cysts. The etiology of this peculiar entity has been debated and theories include a benign neoplasm, a hamartoma or an unusual reactive hyperplasia. There are only seven prior cases reported of ESN in the literature. Our case presented here is the first report to show connection of the ESN to the overlying epidermis and reactive epidermal hyperplasia. This suggests that ESN is indeed an unusual form of benign reactive hyperplasia. In addition, the clinical setting in this case was of pruritus and scratching in a background of papular urticaria, supporting the previous notion that ESN is probably a response to an external stimulus such as rubbing.

Primary apocrine adenocarcinoma of the axilla.

Primary apocrine adenocarcinoma (AA) is a rare malignant cutaneous neoplasm that typically arises in areas of high apocrine gland density such as the axillae and the anogenital region. Due to the nonspecific clinical manifestation of AA, the differential diagnosis may be broad. The rarity of this neoplasm has led to a relative lack of well-established histologic and immunohistochemical diagnostic criteria, further complicating the diagnosis of AA. We report the case of a 49-year-old man with primary AA of the left axilla and provide a review of the clinical and histologic findings, epidemiology, and treatment modalities of this rare cutaneous neoplasm.

Fluorescence in situ hybridization (FISH) as an aid for the diagnosis of graft-versus-host disease in two multivisceral organ transplant patients.

We herein describe 2 cases of adult multivisceral transplant patients who developed graft-versus-host disease manifesting predominantly as lichenoid skin papules and plaques. The diagnosis was supported by histopathology but ultimately corroborated by the utilization of the fluorescence in situ hybridization (FISH) technique using X and Y chromosome probes on unstained biopsy slides. In both cases, FISH revealed a high percentage of donor-derived cells as part of the inflammatory infiltrate in the skin biopsy. This report adds to the previous publications showing the utility of FISH in corroborating the diagnosis of graft-versus-host disease in transplant patients with unmatched sex donor.

Loss of the platelet activating factor receptor in mice augments PMA-induced inflammation and cutaneous chemical carcinogenesis.

Although platelet-activating factor (PAF) is a well-known acute inflammatory mediator, little is known regarding the role of PAF in chronic inflammation. Phorbol esters are known to stimulate PAF production. Moreover, the ability of repeated applications of phorbol esters to induce a sustained inflammatory response is crucial to their tumorigenic activity. We therefore examined whether PAF acts as a mediator of phorbol ester-induced inflammation and tumorigenesis. While PAF receptor knockout mice (PAFR(-/-)) showed an expected but modest reduction in the acute inflammatory response to phorbol 12-myristate 13-acetate (PMA), these mice exhibited a surprising increase in inflammation following chronic PMA application. This increased inflammation was documented by a number of findings that included: increased skin thickness, increased myeloperoxidase activity and expression and increased expression of known inflammatory mediators. Interestingly, vehicle-treated PAFR(-/-) mice also exhibited modest increases in levels of inflammatory markers. This suggests that the platelet activating factor receptor (PAFR) acts to suppress chronic inflammation in response to other stimuli, such as barrier disruption. The idea that chronic PAFR activation is anti-inflammatory was documented by repetitive topical PAFR agonist administration that resulted in reduced myeloperoxidase activity in skin. We next utilized a 7,12-dimethylbenz(a)anthracene/PMA carcinogenesis protocol to demonstrate that PAFR(-/-) mice exhibit significantly increased tumor formation and malignant progression compared with wild-type control mice. These studies provide evidence for two important, unexpected and possibly interrelated pathological roles for the PAFR: first, the PAFR acts to suppress PMA-induced chronic inflammation; secondly, the PAFR acts to suppress neoplastic development in response to chemical carcinogens.

Massive localized lymphedema: A soft tissue process that may present to dermatologists.

Massive localized lymphedema (MLL) is a clinically and histologically distinct entity seen in morbidly obese patients. We describe two obese patients with MLL in the lower abdomen and suprapubic area. Biopsies showed characteristic histologic features of an expanded dermis with lymphangiectases, fibrotic septae and focal fat necrosis. One patient had long-standing hypothyroidism, an association previously reported. This disease is frequently complicated by recurrent cellulitis and may be amenable to surgery. Patients with MLL may present to dermatologists, and this disease has characteristic histopathologic findings that may mimic liposarcoma to the unaware dermatopathologist.

CD8-positive lymphomatoid papulosis (type D): Some lesions may lack CD30 expression and overlap histologically with mycosis fungoides.

BACKGROUND: CD8+ lymphomatoid papulosis is frequently indistinguishable histopathologically from primary cutaneous aggressive epidermotropic CD8+ T-cell lymphoma except for the expression of CD30. However, absent or weak expression of CD30 has been rarely reported in cases of CD8+ LyP. OBJECTIVE: We aim to study the clinical and pathologic features of cases of CD8+ LyP with no or minimal expression of CD30. MATERIAL AND METHODS: We identified all cases of CD8+ LyP diagnosed in our institution over a period of 10 years. Blinded comparison of clinical and histopathologic features of cases with and without CD30 expression was performed. RESULTS: Among seven cases (four patients) with definitive clinical and histopathologic diagnosis of CD8+ LyP, two cases (29%) had no expression of CD30. These two cases had more prominent epidermotropism, less epidermal ulceration, and less vascular damage relative to cases with CD30 expression and therefore resembled mycosis fungoides and type B LyP. CD5 and CD7 were frequently lost regardless of the CD30 status. Expression of cytotoxic markers was not different between the two groups. In the two cases with lack of CD30 expression, subsequent biopsies showed classic features of CD8+ LyP with strong expression of CD30. CONCLUSION: CD8+ LyP with lack of expression of CD30 may have distinct histopathologic features that resemble mycosis fungoides and LyP type B. Clinically, they are indistinguishable from their CD30+ counterparts, signifying the importance of clinical correlation to avoid the erroneous diagnosis of lymphoma. Interval biopsies may be needed to establish a definitive diagnosis.

Desmoglein-1 is a minor autoantigen in dogs with pemphigus foliaceus.

The majority of human patients with pemphigus foliaceus (PF) have circulating IgG autoantibodies that target conformational epitopes on the desmosomal cadherin desmoglein-1 (dsg1). Limited studies using immunoblot techniques suggested that the principal autoantigen in dogs with PF might also be dsg1. It was the objective of this study to test this hypothesis. A comprehensive survey of canine PF sera was conducted using a novel screening strategy that detects conformational epitopes. This method consists of the ectopic expression of canine dsg1 at the surface of human 293T epithelial kidney cells and their live screening, i.e. prior to fixation. Out of seven control human PF sera that bound to canine epidermis, three (57%) contained IgG autoantibodies that recognized ectopically expressed canine dsg1 with a membrane and punctate pattern. Out of 83 canine PF sera only five (6%) contained IgG that recognized canine dsg1. Consistent with findings for human PF sera obtained in this study, autoantibody binding was conformation- and glycosylation-dependent as demonstrated by calcium chelation with EDTA and tunicamycin or wheat germ agglutinin treatment, respectively. In conclusion, these studies establish canine dsg1 as a minor autoantigen for canine PF. Antigenic epitopes appear to be conformation- and glycosylation-dependent.

Identification of a potential effector function for IgE autoantibodies in the organ-specific autoimmune disease bullous pemphigoid.

Bullous pemphigoid (BP) is an autoimmune skin disease characterized by autoantibodies against the hemidesmosomal protein BP180. In addition to IgG autoantibodies, IgE class autoantibodies have been reported in BP patients. Because animal models utilizing only IgG antibodies do not totally replicate human BP, we examined the specificity and potential relevance of IgE autoantibodies in this disease. Thirty BP patients participated in these studies. Serum IgE was measured and the IgE specificity was determined by immunoblotting. Double labeling Immunofluorescence was performed using combinations of specific antibodies to human mast cell tryptase, IgE and BP180. BP180-stimulated histamine release was measured from basophils of untreated BP patients (n=9), BP patients undergoing immunosuppressive therapy (n=9) and controls (n=16). Elevated IgE levels were found In 70% of untreated BP patients. IgE autoantibodies directed against BP180 were detected in 86% of untreated patients and in all but one of these patients the IgE reacted with the NC16A domain of BP180. IgE-coated mast cells were detected in perilesional skin of the BP patients. Moreover, BP180 peptides were detected on these mast cells. BP180-stimulated histamine release was significantly higher in basophils obtained from untreated BP patients compared with control basophils (p=0.006) or from treated BP patients (p=0.01). These findings support the hypothesis that IgE autoantibodies are involved in the pathogenesis of BP. IgE and IgG BP autoantibodies share the same antigenic specificity. Antigen-specific degranulation of basophils and/or mast cells from BP patients suggests a mechanism by which IgE may contribute to lesion development.

A subset of pemphigus foliaceus patients exhibits pathogenic autoantibodies against both desmoglein-1 and desmoglein-3.

In pemphigus vulgaris the major pathogenic antibody binds desmoglein-3, and mediates mucosal disease. Development of cutaneous disease is associated with acquisition of antibodies to desmoglein-1. In pemphigus foliaceus, and its endemic form, fogo selvagem by contrast, the major pathogenic antibody recognizes desmoglein-1 and mediates cutaneous disease only. In this study, we sought to determine the prevalence of antibodies to desmoglein-3 in patients with pemphigus foliaceus and fogo selvagem. We produced recombinant desmoglein-1 and desmoglein-3, and used them in highly sensitive and specific enzyme-linked immunosorbent assays, as well as immunoprecipitation assays. We detected antibodies to desmoglein-3 in 19 of 276 patients with pemphigus foliaceus and fogo selvagem, who had cutaneous disease only. We showed that these antibodies to desmoglein-3 could be absorbed in a concentration-dependent manner by desmoglein-3 but not by desmoglein-1. Also antibodies to desmoglein-1 could be absorbed in a concentration-dependent manner by desmoglein-1 but not desmoglein-3. This suggests that two separate species of antibody are present rather than one antibody capable of cross-reacting with both desmoglein-1 and desmoglein-3. Finally, it was shown that affinity-purified antibodies to desmoglein-3 from patients with pemphigus foliaceus and fogo selvagem induced a pemphigus vulgaris-like skin disease in mice by passive transfer. These results suggest that a subset of patients with pemphigus foliaceus and fogo selvagem have antibodies to desmoglein-3 that may be involved in the pathogenesis of their cutaneous disease.

Topical application of a platelet activating factor receptor agonist suppresses phorbol ester-induced acute and chronic inflammation and has cancer chemopreventive activity in mouse skin.

Platelet activating factor (PAF) has long been associated with acute edema and inflammatory responses. PAF acts by binding to a specific G-protein coupled receptor (PAF-R, Ptafr). However, the role of chronic PAF-R activation on sustained inflammatory responses has been largely ignored. We recently demonstrated that mice lacking the PAF-R (Ptafr-/- mice) exhibit increased cutaneous tumorigenesis in response to a two-stage chemical carcinogenesis protocol. Ptafr-/- mice also exhibited increased chronic inflammation in response to phorbol ester application. In this present study, we demonstrate that topical application of the non-hydrolysable PAF mimetic (carbamoyl-PAF (CPAF)), exerts a potent, dose-dependent, and short-lived edema response in WT mice, but not Ptafr -/- mice or mice deficient in c-Kit (c-KitW-sh/W-sh mice). Using an ear inflammation model, co-administration of topical CPAF treatment resulted in a paradoxical decrease in both acute ear thickness changes associated with a single PMA application, as well as the sustained inflammation associated with chronic repetitive PMA applications. Moreover, mice treated topically with CPAF also exhibited a significant reduction in chemical carcinogenesis. The ability of CPAF to suppress acute and chronic inflammatory changes in response to PMA application(s) was PAF-R dependent, as CPAF had no effect on basal or PMA-induced inflammation in Ptafr-/- mice. Moreover, c-Kit appears to be necessary for the anti-inflammatory effects of CPAF, as CPAF had no observable effect in c-KitW-sh/W-sh mice. These data provide additional evidence that PAF-R activation exerts complex immunomodulatory effects in a model of chronic inflammation that is relevant to neoplastic development.

Spatiotemporal assessments of dermal hyperemia enable accurate prediction of experimental cutaneous carcinogenesis as well as chemopreventive activity.

Field cancerization refers to areas of grossly normal epithelium that exhibit increased risk for tumor occurrence. Unfortunately, elucidation of the locoregional changes that contribute to increased tumor risk is difficult due to the inability to visualize the field. In this study, we use a noninvasive optical-based imaging approach to detail spatiotemporal changes in subclinical hyperemia that occur during experimental cutaneous carcinogenesis. After acute inflammation from 10 weeks of UVB irradiation subsides, small areas of focal hyperemia form and were seen to persist and expand long after cessation of UVB irradiation. We show that these persistent early hyperemic foci reliably predict sites of angiogenesis and overlying tumor formation. More than 96% of the tumors (57 of 59) that developed following UVB or 7,12-dimethylbenz(a)anthracene/phorbol 12-myristate 13-acetate (DMBA/PMA) treatment developed in sites of preexisting hyperemic foci. Hyperemic foci were multifocal and heterogeneously distributed and represented a minor fraction of the carcinogen-treated skin surface (10.3% of the imaging area in vehicle-treated animals). Finally, we also assessed the ability of the anti-inflammatory agent, celecoxib, to suppress hyperemia formation during photocarcinogenesis. The chemopreventive activity of celecoxib was shown to correlate with its ability to reduce the area of skin that exhibit these hyperemic foci, reducing the area of imaged skin containing hyperemic foci by 49.1%. Thus, we propose that a hyperemic switch can be exploited to visualize the cancerization field very early in the course of cutaneous carcinogenesis and provides insight into the chemopreventive activity of the anti-inflammatory agent celecoxib.

Progression of toxic epidermal necrolysis after tanning bed exposure.

BACKGROUND: In addition to recreational tanning bed use, UV radiation exposures are sometimes sought to self-treat skin conditions. The ability of tanning bed radiation exposure to trigger toxic epidermal necrolysis has not been reported. OBSERVATIONS: A young woman attempted to treat a self-limiting drug hypersensitivity reaction via tanning bed radiation exposure, which resulted in a systemic toxic epidermal necrolysis-like reaction. Studies with cultured keratinocytes and an epithelial cell line reveal that UV-A radiation can synergize with other stimuli such as phorbol esters or interleukin 1 to produce large amounts of tumor necrosis factor, providing a potential mechanism for this exaggerated reaction. CONCLUSION: In addition to inducing photodamage and skin cancer, tanning bed radiation exposure can trigger a toxic epidermal necrolysis-like reaction, possibly via the exaggerated production of keratinocyte cytokines such as tumor necrosis factor.

Characterization of a subgroup of patients with dermatitis herpetiformis with nonclassical histologic features.

Dermatitis herpetiformis (DH) is an autoimmune disease mediated by IgA antibodies. The diagnosis of DH is based on clinical presentation, biopsy for hematoxylin and eosin, and direct immunofluorescence. The chief hematoxylin and eosin finding is a subepithelial blister with neutrophils in dermal papillae. The direct immunofluorescence findings are deposition of IgA and sometimes C3 at the basement membrane with accentuation in dermal papillae. Immunofluorescence is thought to be a sensitive and specific assay in DH, and there are no other known diseases with this pattern of immunofluorescence. The aim of this project was to determine the prevalence of nonclassical histologic findings in DH. We studied 24 cases of DH received at our institution. All cases had clinical findings of DH as well as positive direct immunofluorescence with IgA. We found that 9 of 24 cases (37.5%) had nonspecific H&E findings of a lymphocytic infiltrate only with fibrosis in the dermal papillae and ectatic capillaries. The remaining 15 cases had classic findings of multilocular neutrophilic microabscesses in the dermal papillae. These findings were reproduced on step sectioning. These findings suggest that routine histology may be quite nonspecific in DH and direct immunofluorescence or other more specific immunologic assay is an essential adjunct to diagnosis.

Environmental risk factors in endemic pemphigus foliaceus (fogo selvagem).

An ongoing sero-epidemiological study of the Terena reservation of Limao Verde, known to have a high prevalence and incidence of FS, has revealed important information about this autoimmune disease. During surveillance of this population of approximately 1,200, which began in 1994, we documented 43 FS cases and studied the transition from the normal state to the disease state in several of these individuals. Furthermore, we established that FS patients as well as a large number of normal individuals on the reservation possess anti-dsg1 autoantibodies. The following interesting observations were made: (1) the ectodomain of dsg1 contains epitopes recognized by both autoantibodies and T cells from FS patients; (2) pathogenic anti-dsg1 autoantibodies in FS belong to the IgG4 subclass; (3) nonpathogenic anti-dsg1 autoantibodies of the IgG1 subclass were detected in normal individuals from Limao Verde and in patients in the preclinical stage of the disease; (4) anti-dsg1 autoantibodies from normal individuals and patients in the preclinical stage of FS recognize the EC5 domain of dsg1, whereas pathogenic anti-dsg1 autoantibodies bind the EC1/EC2 domains; (5) houses of FS patients are rustic, with thatched roofs and walls and dirt floors; (6) there was a high frequency of hematophagous insects (bedbugs and kissing bugs) in the houses of FS patients; (7) previous studies revealed that the predominant black fly on this reservation belongs to the species Simunlium nigrimanum. These findings suggest that the environmental antigen(s) triggering the autoimmune response in FS may be linked to exposure to hematophagous insects.