Amplification of Mutant NRAS in Melanocytic Tumors With Features of Spitz Tumors.

NRAS activating mutations are prevalent in melanocytic neoplasia, occurring in a subset of common acquired melanocytic nevi and ∼30% of cutaneous melanomas. In this study, we described a cohort of 7 distinctive melanocytic tumors characterized by activating point mutations in codon 61 of NRAS with amplification of the mutant NRAS allele and shared clinicopathologic features. These tumors occurred predominantly in younger patients, with a median age of 20 years (range, 6-56 years). They presented as papules on the helix of the ear (4 cases) or extremities (3 cases). Microscopically, the tumors were cellular, relatively well-circumscribed, compound, or intradermal proliferations. The tumor cells often extended into the deep reticular dermis and involved the superficial subcutaneous fat in some cases. The melanocytes were epithelioid to spindled with moderate amounts of cytoplasm and conspicuous nucleoli. They were arranged in short plexiform fascicles, nests, and cords. Some cases had occasional pleomorphic and multinucleated melanocytes. Rare dermal mitotic figures were present in all cases. The dermis contained thick collagen bundles and minimal solar elastosis. Follow-up data were available for 5 patients, with a median period of 4.2 years (range, 1-9 years), during which no recurrences or metastases were reported. Our series highlights a clinicopathologically and molecularly distinctive subset of NRAS-mutated tumors with amplification of the mutant NRAS allele.

Atypical Spitz tumor with SQSTM1::NTRK2 fusion: Report of a case with unique spindled cell features.

A host of signature genetic alterations have been demonstrated in Spitz neoplasms, most notably fusions of kinase genes (including BRAF, ALK, ROS1, NTRK1, NTRK3, RET, MET, MAP3K8) or variants in HRAS. While there are multiple reports of rearrangements involving NTRK1 and NTRK3 in Spitz tumors, there are very few reports of NTRK2-rearranged Spitz nevi in the literature. This report presents an NTRK2-rearranged atypical Spitz tumor with spindled cell features. The patient was a 6-year-old female with a growing pigmented papule on the back. Histopathological evaluation revealed an asymmetric, biphasic, compound proliferation of melanocytes featuring an epithelioid cell population arranged as variably sized nests and single cells along the basal layer with extension down adnexa, as well as a population of spindled melanocytes with desmoplastic features and loss of Melan-A expression in the dermis. There was partial loss of p16 expression in the epidermal component and diffuse loss in the dermal component. Immunohistochemistry for PRAME, ALK, NTRK1, HRAS Q61R, p53, and BRAF V600E were negative. A SQSTM1::NTRK2 fusion was identified by RNA sequencing. No TERT promoter hotspot variants were detected. This case report expands the known histopathologic spectrum of genetic alterations in Spitz neoplasms.

Histologic and Genetic Features of 51 Melanocytic Neoplasms With Protein Kinase C Fusion Genes.

Fusion genes involving homologs of protein kinase C (PKC) have been identified in a variety of tumors. We report the clinical and histologic presentation of 51 cutaneous melanocytic neoplasms with a PKC fusion gene (involving PRKCA in 35 cases, PRKCB in 15 cases, and PRKCG in a single case). Most tumors were in young adults (median age, 29.5 years; range, 1-73 years) but some presented in newborns. Histologically, 42 tumors were classified as benign, presenting predominantly as biphasic dermal proliferation (88%) with nests of small melanocytes surrounded by fibrosis with haphazardly arranged spindled and dendritic melanocytes, resembling those reported as "combined blue nevi." Most tumors (60%) were heavily pigmented and in 15%, hyperpigmented epithelioid melanocytes were present at the dermoepidermal junction. Two lesions were paucicellular and showed marked sclerosis. Three tumors, including 2 proliferating nodules, were considered intermediate grade. Six tumors had sheets of atypical melanocytes infiltrating the dermis and were classified as melanomas. Two of the melanomas displayed loss of BAP1 nuclear expression. The median follow-up time was 12 months, with 1 patient alive with metastatic disease and 1 dying of their melanoma. These results suggest that melanocytic tumors with PKC fusion genes have characteristic histopathologic features, which are more similar to blue nevi than to pigmented epithelioid melanocytomas. As is the case with GNA-mutated blue nevi, they can progress to melanomas via BAP1 inactivation and metastasize.

Microsecretory adenocarcinoma of the skin harboring recurrent SS18 fusions: A cutaneous analog to a newly described salivary gland tumor.

BACKGROUND: Microsecretory adenocarcinoma (MSA) is a newly described salivary gland neoplasm characterized by MEF2C::SS18 fusions. MSA was previously thought to occur exclusively in salivary glands. Here, we expand the spectrum of known primary sites of this tumor by describing a series of cutaneous tumors with analogous findings. METHODS: We identified four cutaneous primary tumors with histopathologic features identical to MSA of the salivary glands. These cases were evaluated by immunohistochemistry, fluorescence in situ hybridization (FISH) for SS18 rearrangement and targeted RNA-sequencing. We also queried a pan-tumor database of advanced carcinomas for MEF2C::SS18. RESULTS: The cases occurred in men ranging from 61 to 74 years (mean, 68). They arose from the skin of the nose, chin, scalp, and external auditory canal. All included cords/microcysts of eosinophilic cells with bland oval nuclei and bluish mucin within fibromyxoid stroma. The scalp tumor also exhibited high-grade transformation (marked atypia, elevated mitotic rate, and necrosis), a feature unreported in salivary MSA. By immunohistochemistry, all cases were positive for S100. Two showed a myoepithelial component positive for p40 and smooth muscle actin or calponin. Three cases harbored MEF2C::SS18 by RNA sequencing, while one with limited tissue had SS18 rearrangement via FISH. Two patients had no evidence of recurrence or metastasis in limited follow-up (3 and 6 months). The pan-tumor database query also did not identify MEF2C::SS18 in any advanced cutaneous carcinomas. CONCLUSION: This report expands the sites that can be involved by MSA. Similar to salivary cases, MEF2C::SS18 represents a recurrent fusion in MSA of the skin. Unusual features in cutaneous cases not seen in salivary MSA include one case with high-grade transformation and two cases with a myoepithelial cell component. Identification of this fusion expands the spectrum of salivary-analog cutaneous tumors and aids in precise tumor classification.

Cutaneous angiosarcoma presenting as bilateral periorbital edema.

A 66-year-old man presented with chronic bilateral periorbital edema with associated yellowish hue, scattered violaceous smooth macules and contracture of the forehead. He had undergone dental surgery 3 months prior to symptom onset. Laboratory workup for common causes of eyelid edema was unremarkable and MRI of the orbits was unrevealing. The patient did not respond to oral corticosteroids or antibiotics. Punch biopsies were obtained which revealed atypical lymphatic endothelial cells consistent with a diagnosis of cutaneous angiosarcoma.The patient was deemed not to be a surgical candidate and underwent 3 cycles of immunotherapy with limited response. He declined further treatment and transitioned to hospice care. Although cutaneous angiosarcoma uncommonly involves the periorbital region, it should be considered in the differential diagnosis of eyelid edema as early recognition and treatment are critical to prevent rapid intradermal spread and metastases.

Histopathologic and genetic findings in atypical spindle cell/pleomorphic lipomatous tumors and atypical pleomorphic fibromas.

BACKGROUND: Spindle cell lipomas, pleomorphic lipomas (SCL/PLs), and pleomorphic fibromas (PF) are tumors with loss of retinoblastoma (RB). The latest World Health Organization classification includes a category of atypical spindle cell/pleomorphic lipomatous tumors (ASPLT), which encompasses tumors in this spectrum that show atypical histopathologic features. We have observed PFs that show similar atypical features. METHODS: Cases of SCL/PL and PF with atypical features were collected from tissue archives between 2010 and 2019. Genetic alterations were investigated using array comparative genomic hybridization (aCGH). RESULT: Of 15 cases found, most tumors were dermal based with fibrocytic or fibroadipocytic appearance and occasional lipoblasts. All cases had a high proliferation index with atypical mitotic figures in 71% of cases. Chromosome 13q loss was present in all cases with CGH data. Additional recurrent chromosomal losses included 17p, 16q, 17q, 20p, 4, and 10. No recurrence was found in limited follow-up. CONCLUSIONS: ASPLTs are characterized by loss of RB, prominent nuclear pleomorphism, mitotic activity including atypical mitotic figures, and genomic instability with multiple chromosomal aberrations. A similar group of tumors with these histopathologic features lacks lipomatous differentiation, and we propose the diagnosis of atypical PF as a fibromatous variant of ASPLT. Limited clinical follow-up appears benign.

Cicatricial pemphigoid Brunsting-Perry variant masquerading as neutrophil-mediated cicatricial alopecia.

A 72-year-old male presented with scarring alopecia on the scalp vertex, multiple crusted plaques on the hairline, and a history of vesicular eruption on the face. The scalp showed crusted plaques with loss of follicular ostia. No follicular pustules or compound follicles were present. An initial transverse scalp biopsy showed perifollicular neutrophils, lymphocytes, and plasma cells along with dermal fibrosis. Focal epidermal/dermal and follicular/adventitial dermal clefts were apparent but were thought to be secondary to fibrosis, and the biopsy result was interpreted to represent a neutrophil-mediated cicatricial alopecia. Concurrently, direct immunofluorescence (DIF) analysis showed linear junctional deposition of IgG and C3. A repeat scalp biopsy revealed more prominent epidermal/dermal clefts, fibrosis, mixed infiltrate with neutrophils, lymphocytes, histiocytes, and plasma cells, as well as prominent follicular/adventitial dermal clefts with perifollicular neutrophils. Given the combination of clefts, perijunctional neutrophils, and positive DIF findings, it became clear that this eruption represented the Brunsting-Perry variant of cicatricial pemphigoid. Here, we illustrated that a neutrophil-rich form of cicatricial pemphigoid can masquerade as a neutrophil-mediated scarring alopecia. In evaluating a specimen suspected to be a neutrophil-mediated scarring alopecia, one should be alert to the presence of subepidermal and perifollicular clefting, and consider cicatricial pemphigoid.

Cutaneous Leishmaniasis Caused by an Unknown Leishmania Strain, Arizona, USA.

We investigated an autochthonous case of cutaneous leishmaniasis caused by a genetically different Leishmania sp. in a patient in Arizona, USA. This parasite was classified into the subgenus Leishmania on the basis of multilocus DNA sequence and phylogenetic analyses of the rRNA locus and 11 reference genes.

Fusion partners of NTRK3 affect subcellular localization of the fusion kinase and cytomorphology of melanocytes.

A subset of Spitz tumors harbor fusions of NTRK3 with ETV6, MYO5A, and MYH9. We evaluated a series of 22 melanocytic tumors in which an NTRK3 fusion was identified as part of the diagnostic workup. Tumors in which NTRK3 was fused to ETV6 occurred in younger patients were predominantly composed of epithelioid melanocytes and were classified by their histopathologic features as Spitz tumors. In contrast, those in which NTRK3 was fused to MYO5A were predominantly composed of spindled melanocytes arrayed in fascicles with neuroid features such as pseudo-Verocay bodies. To further investigate the effects of the fusion kinases ETV6-NTRK3 and MYO5A-NTRK3 in melanocytes, we expressed them in immortalized melanocytes and determined their subcellular localization by immunofluorescence. ETV6-NTRK3 was localized to the nucleus and diffusely within the cytoplasm and caused melanocytes to adopt an epithelioid cytomorphology. In contrast, MYO5A-NTRK3, appeared excluded from the nucleus of melanocytes, was localized to dendrites, and resulted in a highly dendritic cytomorphology. Our findings indicate that ETV6-NTRK3 and MYO5A-NTRK3 have distinct subcellular localizations and effects on cellular morphology.

BAP1-inactivated melanocytic tumors show prominent centrosome amplification and associated loss of primary cilia.

BACKGROUND: BRCA1-associated protein (BAP1) is a tumor suppressor whose loss is associated with various malignancies. The primary cilium is an organelle involved in signal transduction and cell cycle progression. Primary cilia have been shown to be absent in melanoma but retained to some extent in melanocytic nevi, and the severity of dysplasia influences the degree of cilia loss. Additionally, studies have revealed roles for BAP1 in centrosome and mitotic spindle formation. Because the primary cilium is nucleated on the mother centriole, we examined the connection between the presence of primary cilia and the formation of centrosomes in BAP1-inactivated melanocytic tumors (BIMTs). METHODS: We evaluated the cilia and centrosomes in 11 BIMTs and five conventional melanocytic nevi using immunofluorescence staining of acetylated alpha-tubulin and gamma-tubulin. RESULTS: We found that, compared to nevi, BIMTs show loss of primary cilia and amplification of centrosomes. Occasional nevi also showed increased centrioles; however, these foci of amplification were more likely to be ciliated than those in BIMTs. CONCLUSIONS: Although centrosome amplification does not absolutely correlate with loss of primary cilia in melanocytic neoplasms, absence of BAP1 exacerbates the phenotype. Moreover, aberrant centrosome and cilia formation are likely critical in the pathogenesis of other BAP1-inactivated tumors.

Desmoplastic Trichoepithelioma With Pseudocarcinomatous Hyperplasia: A Folliculosebaceous Neoplasm in Young Persons.

ABSTRACT: Pseudocarcinomatous desmoplastic trichoepithelioma (PDTE) features verrucous squamous epidermal hyperplasia with a jagged undersurface overlying cords of follicular germinative cells in a fibrotic stroma. To date, only 5 cases have been reported. We identified 7 new PDTEs from 2 institutions and reviewed their clinical manifestations and immunohistochemical profile. The median age was 14 years (range 8-34 years). New findings included vacuolization of the basal layer of the pseudocarcinomatous surface epithelium, and the frequent presence of singly distributed sebocytes within the cords of basaloid cells. The immunohistochemical profile resembles desmoplastic trichoepithelioma, with expression of TDAG51, CK15, and Ber-Ep4. Colonizing CK20+ Merkel cells were present in all cases. PDTE needs to be differentiated from malignant neoplasms such as squamous cell carcinoma, morphoeic basal cell carcinoma, and microcystic adnexal carcinoma. Recognizing the features of this sclerosing folliculosebaceous neoplasm facilitates accurate diagnosis and avoids overtreatment.

Spitz melanoma is a distinct subset of spitzoid melanoma.

Melanomas that have histopathologic features that overlap with those of Spitz nevus are referred to as spitzoid melanomas. However, the diagnostic concept is used inconsistently and genomic analyses suggest it is a heterogeneous category. Spitz tumors, the spectrum of melanocytic neoplasms extending from Spitz nevi to their malignant counterpart Spitz melanoma, are defined in the 2018 WHO classification of skin tumors by the presence of specific genetic alterations, such as kinase fusions or HRAS mutations. It is unclear what fraction of "spitzoid melanomas" defined solely by their histopathologic features belong to the category of Spitz melanoma or to other melanoma subtypes. We assembled a cohort of 25 spitzoid melanomas diagnosed at a single institution over an 8-year period and performed high-coverage DNA sequencing of 480 cancer related genes. Transcriptome wide RNA sequencing was performed for select cases. Only nine cases (36%) had genetic alterations characteristic of Spitz melanoma, including HRAS mutation or fusion involving BRAF, ALK, NTRK1, or MAP3K8. The remaining cases were divided into those with an MAPK activating mutation and those without an MAPK activating mutation. Both Spitz melanoma and spitzoid melanomas in which an MAPK-activating mutation could not be identified tended to occur in younger patients on skin with little solar elastosis, infrequently harbored TERT promoter mutations, and had a lower burden of pathogenic mutations than spitzoid melanomas with non-Spitz MAPK-activating mutations. The MAPK-activating mutations identified affected non-V600 residues of BRAF as well as NRAS, MAP2K1/2, NF1, and KIT, while BRAF V600 mutations, the most common mutations in melanomas of the WHO low-CSD category, were entirely absent. While the "spitzoid melanomas" comprising our cohort were enriched for bona fide Spitz melanomas, the majority of melanomas fell outside of the genetically defined category of Spitz melanomas, indicating that histomorphology is an unreliable predictor of Spitz lineage.

Melanocytic tumors with MAP3K8 fusions: report of 33 cases with morphological-genetic correlations.

We report a series of 33 skin tumors harboring a gene fusion of the MAP3K8 gene, which encodes a serine/threonine kinase. The MAP3K8 fusions were identified by RNA sequencing in 28 cases and by break-apart FISH in five cases. Cases in which fusion genes were fully characterized demonstrated a fusion of the 5' part of MAP3K8 comprising exons 1-8 in frame to one of several partner genes at the 3' end. The fusion genes invariably encoded the intact kinase domain of MAP3K8, but not the inhibitory domain at the C-terminus. In 13 (46%) of the sequenced cases, the 3' fusion partner was SVIL. Other recurrent 3' partners were DIP2C and UBL3, with additional fusion partners that occurred only in a single tumor. Clinically, the lesions appeared mainly in young adults (2-59 years of age; median = 18), most commonly involving the lower limbs (55%). Five cases were diagnosed as Spitz nevus, 13 as atypical Spitz tumor, and 15 as malignant Spitz tumor. Atypical and malignant cases more commonly occurred in younger patients. Atypical Spitz tumors and malignant Spitz tumors cases tended to show epidermal ulceration (32%), a dermal component with giant multinucleated cells (32%), and clusters of pigmented cells in the dermis (32%). Moreover, in atypical and malignant cases, a frequent inactivation of CDKN2A (21/26; 77%) was identified either by p16 immunohistochemistry, FISH, or comparative genomic hybridization. Gene expression analysis revealed that MAP3K8 expression levels were significantly elevated compared to a control group of 57 Spitz lesions harboring other known kinase fusions. Clinical follow-up revealed regional nodal involvement in two of six cases, in which sentinel lymph node biopsy was performed but no distant metastatic disease after a median follow-up time of 6 months.

Melanotic Schwannoma of the Vulva: A Case Report and Review of the Literature.

Melanotic schwannoma is a pigmented tumor of peripheral nerve differentiation. Primary cutaneous presentations are extremely rare, as the bulk of melanotic schwannomas tend to develop in paraspinal and axial sites. Tumors arise sporadically and in the setting of the Carney complex. Alterations in the gene encoding protein kinase A regulatory subunit-α (PRKAR1A) underlie most patients with the Carney complex and mediate melanotic schwannoma tumorigenesis. Melanotic schwannomas from noncutaneous sites can locally recur and metastasize widely, leading to a recent proposal to change the nomenclature to "malignant melanotic schwannian tumor." However, the clinicopathologic features of primary cutaneous melanotic schwannomas are relatively unexplored. We present a case of a nodule arising on the vulva of a 34-year-old woman. Microscopically, a dermal-based, heavily pigmented proliferation of plump spindled and epithelioid cells arrayed in nodules and fascicles was seen. Lesional cells stained positively for S100, Melan-A, and BAP1 but were negative for Prkar1α. Next-generation sequencing of a panel of 480 cancer-associated genes revealed that the tumor harbored a PRKAR1A p.S299fs truncating mutation and copy neutral loss of heterozygosity of chromosome 17q, the locus at which PRKAR1A resides. Importantly, no other genetic abnormalities or chromosomal copy number changes were identified. On the basis of combined histopathologic, immunohistochemical, and genetic features, a diagnosis of melanotic schwannoma was rendered. Overall, we present the first clinicopathologic description of a vulvar melanotic schwannoma, review the literature concerning cutaneous presentations of melanotic schwannoma, and propose that melanotic schwannian tumors native to skin may behave more indolently than their noncutaneous counterparts.

Expanding the clinical spectrum of dermal hyperneury: report of nine new cases and a review of the literature.

AIMS: Dermal hyperneury is defined as the hypertrophy of small nerves in the dermis. It has been described in a variety of settings. We present a series of nine new cases with a distinctive clinical presentation and review the existing literature. The aim of the study was to summarise the clinical, histopathological and immunohistochemical findings in a case series of dermal hyperneury with unique clinical presentation. METHODS AND RESULTS: Nine cases were identified from the referral practice of one of the authors. Clinical characteristics, including demographic details, were collated. The histopathological features and novel immunohistochemical findings were analysed. Four cases presented with multiple skin lesions. Clinical evaluation revealed no associated syndromic stigmata. The histology in all cases was that of dermal hyperneury. Immunohistochemistry for phosphatase and tensin homologue (PTEN) and RET was supportive of the lack of syndromic association. CONCLUSION: The presentation of dermal hyperneury with multiple cutaneous lesions and no syndromic associations is distinctive, and no study with PTEN and RET immunohistochemistry has previously been reported. Comparisons with recent reports of multiple non-syndromic mucocutaneous neuromas are discussed.

Acute inflammatory edema: A mimicker of cellulitis in critically ill patients.

BACKGROUND: Inpatient dermatology consultations for treatment-refractory or atypical cellulitis are common. In critically ill patients, differentiating cellulitis from its mimickers can be challenging. OBJECTIVE: We describe acute inflammatory edema, a likely underrecognized variant of pseudocellulitis. METHODS: We reviewed the charts of 15 patients with this diagnosis, seen by the inpatient dermatology consultation service at the University of California at San Francisco between 2009 and 2017. RESULTS: The cohort consisted of 9 women and 6 men with an age range of 52-73 years. Acute inflammatory edema presents as bilateral, erythematous, and edematous plaques, most commonly involving the thighs and lower abdomen, sparing areas of increased pressure on the skin. There is a predilection for patients with high body mass index and those with clinical or quantitative findings of fluid overload. CONCLUSION: We propose a 3-part pathogenesis of acute inflammatory edema: 1) acute-onset volume overload 2) in patients with impaired lymphatic return 3) leads to dermal edema, microtears in connective tissue, and an influx of inflammation.

Hypercellular Encapsulated Neuroma Imitating Desmoplastic Melanoma.

Palisaded encapsulated neuromas (PENs) are benign cutaneous nerve sheath proliferations that typically occur as flesh-colored papules solitarily on the head and neck in adults, with a slight predilection for females. Histopathologically, they are partially or completely encapsulated intradermal nodules with Schwann cells and axons in fascicles separated by clefts. Although these features are often characteristic, the hypercellular variant of PEN can pose a diagnostic challenge in distinguishing between other cellular neural and melanocytic lesions. We herein report a case of hypercellular PEN, which showed striking similarity to desmoplastic melanoma.

NTRK3 kinase fusions in Spitz tumours.

Oncogenic fusions in TRK family receptor tyrosine kinases have been identified in several cancers and can serve as therapeutic targets. We identified ETV6-NTRK3, MYO5A-NTRK3 and MYH9-NTRK3 fusions in Spitz tumours, and demonstrated that NTRK3 fusions constitutively activate the mitogen-activated protein kinase, phosphoinositide 3-kinase and phospholipase Cγ1 pathways in melanocytes. This signalling was inhibited by DS-6051a, a small-molecule inhibitor of NTRK1/2/3 and ROS1. NTRK3 fusions expand the range of oncogenic kinase fusions in melanocytic neoplasms and offer targets for a small subset of melanomas for which no targeted options currently exist. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Loss of retinoblastoma in pleomorphic fibroma: An immunohistochemical and genomic analysis.

BACKGROUND: Pleomorphic fibroma is a curious neoplasm that exhibits striking cytologic atypia, yet behaves in benign fashion. The cytologic features include single cells with pleomorphic nuclei and scattered giant cells resembling the neoplastic cells of pleomorphic lipoma, a tumor with known retinoblastoma (Rb) loss. METHODS: We assessed the demographic and histopathologic features of a cohort of 26 pleomorphic fibromas, including assessment with immunostaining for Rb, p16 and Ki-67. Array comparative genomic hybridization (aCGH) was used to assess a limited number of tumors for genomic aberrations. RESULTS: Of the 26 pleomorphic fibromas analyzed, 19 occurred in women and 7 in men, with a mean age of 47 years. The anatomic locations were variable. Immunostaining showed loss of Rb protein expression in all cases and diffuse p16 expression in 85%. Ki-67 labeling rate was below 10% in 85%. Chromosome 13q loss was found in 7 of 7 pleomorphic fibromas assessed with aCGH. Recurrent loss of 17p, 16q and 10q were also found. CONCLUSION: We report recurrent loss of RB1 on chromosome 13q in pleomorphic fibromas, confirmed by both protein expression loss and loss of 13q by aCGH. This result indicates pleomorphic fibroma shares the same genetic abnormalities as spindle cell and pleomorphic lipomas.