Clinical, Morphological and Molecular Features of Spitz tumors.

Spitz tumors represent a heterogeneous group of challenging melanocytic neoplasms, displaying a range of biological behaviors, spanning from benign lesions, Spitz nevi (SN) to Spitz melanomas (SM), with intermediate lesions in between known as atypical Spitz tumors (AST). They are histologically characterized by large epithelioid and/or spindled melanocytes arranged in fascicles or nests, often associated with characteristic epidermal hyperplasia and fibrovascular stromal changes. In the last decade, the detection of mutually exclusive structural rearrangements involving receptor tyrosine kinases ROS1, ALK, NTRK1, NTRK2, NTRK3, RET, MET, serine threonine kinases BRAF and MAP3K8, or HRAS mutation, led to a clinical, morphological and molecular based classification of Spitz tumors. The recognition of some reproducible histological features can help dermatopathologist in assessing these lesions and can provide clues to predict the underlying molecular driver. In this review, we will focus on clinical and morphological findings in molecular Spitz tumor subgroups.

The Impact of Next-generation Sequencing on Interobserver Agreement and Diagnostic Accuracy of Desmoplastic Melanocytic Neoplasms.

Next-generation sequencing (NGS) is increasingly being utilized as an ancillary tool for diagnostically challenging melanocytic neoplasms. It is incumbent upon the pathology community to perform studies assessing the benefits and limitations of these tools in specific diagnostic scenarios. One of the most challenging diagnostic scenarios faced by skin pathologists involves accurate diagnosis of desmoplastic melanocytic neoplasms (DMNs). In this study, 20 expert melanoma pathologists rendered a diagnosis on 47 DMNs based on hematoxylin and eosin sections with demographic information. After submitting their diagnosis, the experts were given the same cases, but this time with comprehensive genomic sequencing results, and asked to render a diagnosis again. Identification of desmoplastic melanoma (DM) improved by 7%, and this difference was statistically significant ( P <0.05). In addition, among the 15 melanoma cases, in the pregenomic assessment, only 12 were favored to be DM by the experts, while after genomics, this improved to 14 of the cases being favored to be DM. In fact, some cases resulting in metastatic disease had a substantial increase in the number of experts recognizing them as DM after genomics. The impact of the genomic findings was less dramatic among benign and intermediate-grade desmoplastic tumors (BIDTs). Interobserver agreement also improved, with the Fleiss multirater Kappa being 0.36 before genomics to 0.4 after genomics. NGS has the potential to improve diagnostic accuracy in the assessment of desmoplastic melanocytic tumors. The degree of improvement will be most substantial among pathologists with some background and experience in bioinformatics and melanoma genetics.

BRAF Mutated and Morphologically Spitzoid Tumors, a Subgroup of Melanocytic Neoplasms Difficult to Distinguish From True Spitz Neoplasms.

Drivers of Spitz neoplasms include activating point mutations in HRAS and Spitz-associated genomic fusions. It has become evident that some BRAF -mutated melanocytic neoplasms can morphologically mimic Spitz tumors (STs). These have been termed BRAF mutated and morphologically spitzoid (BAMS). In this study, 17 experts from the International Melanoma Pathology Study Group assessed 54 cases which included 40 BAMS and 14 true STs. The participants reviewed the cases blinded to the genomic data and selected among several diagnostic options, including BAMS, ST, melanoma, and other. A total of 38% of all diagnostic selections in the BAMS cases were for BAMS, whereas 32% were for ST. In 22 of the BAMS cases, the favored diagnosis was BAMS, whereas in 17 of the BAMS cases, the favored diagnosis was ST. Among the 20 cases in the total group of 54 with the highest number of votes for ST, half were BAMS. Of BAMS, 75% had a number of votes for ST that was within the SD of votes for ST seen among true ST cases. There was poor interobserver agreement for the precise diagnosis of the BAMS (kappa = 0.16) but good agreement that these cases were not melanoma (kappa = 0.7). BAMS nevi/tumors can closely mimic Spitz neoplasms. Expert melanoma pathologists in this study favored a diagnosis of ST in nearly half of the BAMS cases. There are BAMS cases that even experts cannot morphologically distinguish from true Spitz neoplasms.

Clinical, Morphologic, and Molecular Features of MAP3K8 Rearranged Spitz Neoplasms: A Retrospective Study Documenting That Bonafide Spitz Melanomas Are Rare.

Previous studies regarding the clinical behavior of Spitz neoplasms lack genomic characterization. We aim to assess our hypothesis that most MAP3K8 Spitz neoplasms are indolent despite MAP3K8 being the single most common driver of Spitz melanoma. Further, we aim to identify genomic features associated with aggressive behavior and to better characterize the morphology of these cases. We analyzed the outcomes of MAP3K8 Spitz neoplasms. We also performed a meta-analysis of the outcomes of MAP3K8 Spitz from the literature. Morphologic features were compared with other variants of Spitz using a Student t test and χ 2 test. Two of 35 cases resulted in local recurrence and one of these cases had local regional metastasis; all other cases had no evidence of recurrence (mean follow-up time: 33 mo). MAP3K8 Spitz only rarely results in aggressive behavior. Metastatic cases have genomic mutations associated with tumor progression. Morphologically, MAP3K8 Spitz neoplasms frequently showed nodular silhouette, large cell size, epithelioid morphology, and severe nuclear atypia resulting in more frequent diagnosis as Spitz melanoma. Most MAP3K8 Spitz neoplasms have excellent prognoses, apart from rare cases harboring additional genomic abnormalities associated with tumor progression.

Melanoma in infants, caused by a gene fusion involving the anaplastic lymphoma kinase (ALK).

We describe the first cases of pediatric melanoma with ALK fusion gene arising within giant congenital melanocytic nevi. Two newborn boys presented with large pigmented nodular plaques and numerous smaller satellite nevi. Additional expansile nodules developed within both nevi and invasive melanomas were diagnosed before 10 months of age in both boys. Oncogenic driver mutations in NRAS and BRAF were absent in both cases. Instead, oncogenic ZEB2::ALK fusion genes were identified in both the nevus and melanoma developing within the nevus. In both cases, tumors were noted by ultrasound in utero, demonstrated significant nodularity at birth, and progressed to melanoma in the first year of life suggesting that congenital nevi with ALK fusion genes may behave more aggressively than those with other mutations. As ALK kinase inhibitors are effective against a range of tumors with similar ALK fusion kinases, identifying ALK fusion genes in congenital melanocytic nevi may provide an opportunity for targeted therapy.

Risk factors and outcomes of melanoma in children and adolescents: A retrospective multicenter study.

BACKGROUND: Pediatric melanoma presents with distinct clinical features compared to adult disease. OBJECTIVE: Characterize risk factors and negative outcomes in pediatric melanoma. METHODS: Multicenter retrospective study of patients under 20 years diagnosed with melanoma between January 1, 1995 and June 30, 2015 from 11 academic medical centers. RESULTS: Melanoma was diagnosed in 317 patients, 73% of whom were diagnosed in adolescence (age ≥11). Spitzoid (31%) and superficial spreading (26%) subtypes were most common and 11% of cases arose from congenital nevi. Sentinel lymph node biopsy was performed in 68% of cases and positive in 46%. Fatality was observed in 7% of cases. Adolescent patients with melanoma were more likely to have family history of melanoma (P = .046) compared to controls. LIMITATIONS: Retrospective nature, cohort size, control selection, and potential referral bias. CONCLUSION: Pediatric melanoma has diverse clinical presentations. Better understanding of these cases and outcomes may facilitate improved risk stratification of pediatric melanoma.

Melanocyte colonization and pigmentation of breast carcinoma: A case report.

Pigmented mammary Paget disease is a rare variant of mammary Paget disease that is often clinically misdiagnosed as a melanocytic lesion of the skin or nipple-areolar complex. Careful morphological assessment, along with the performance of adequate immunohistochemical stains, will help in achieving the right diagnosis and avoiding misdiagnosis of the entity as malignant melanoma. We report a rare case of pigmented mammary Paget disease with concomitant colonization of the underlying invasive ductal carcinoma by melanocytes mimicking melanoma.

Spitz tumor with RAF1 fusion: A report of 3 cases.

Spitz tumors are melanocytic neoplasms morphologically characterized by spindled and/or epithelioid cells and specific stromal and epidermal changes associated with mutually exclusive fusion kinases involving ALK, ROS1, NTRK1, NTRK2, NTRK3, MET and RET, BRAF and MAP3K8 genes or, less commonly, HRAS mutation. RAF1 fusions have been recently detected in cutaneous melanocytic neoplasms, including conventional melanoma, congenital nevus and BAP-1 inactivated tumors. We report herewith three Spitz neoplasms with a RAF1 fusion, including a previously reported CTDSPL::RAF1 fusion and two novel PPAP2B::RAF1 and ATP2B4::RAF1 fusions. Two cases were classified as Spitz nevus, while the remaining neoplasm was classified as Spitz melanoma at the time of the diagnosis, given 9p21 homozygous deletion and positive sentinel lymph node biopsy. We suggest that RAF1 fused melanocytic neoplasms can represent a novel subgroup of Spitz tumors, with a RAF1 fusion representing an oncogenic driver.

Machine learning identification of patient clusters for cutaneous melanoma.

BACKGROUND: Cutaneous melanoma is a cancer arising in melanocyte skin cells and is the deadliest form of skin cancer worldwide. Although some risk factors are known, accurate prediction of disease progression and probability for metastasis are difficult to ascertain, given the complexity of the disease and the absence of reliable predictive markers. Since early detection and treatment are essential to enhance survival, this study utilizing machine learning (ML) aims to further delineate additional risk factors associated with cutaneous melanoma. METHODS: A Bayesian Gaussian Mixture ML model was created with data from 2056 patients diagnosed with cutaneous melanoma and then used to group the patients into six Clusters based on a Silhouette Score analysis. A t-distributed stochastic neighbor embedding (t-SNE) model was used to visualize the six Clusters. RESULTS: Statistical analysis revealed that Cluster 4 showed a significantly higher rate of metastatic disease, as well as higher Breslow depth at diagnosis, compared to the other five Clusters. Compared to the other five Clusters, patients represented in Cluster 4 also had lower healthcare utilization, fewer dermatology clinic visits, fewer primary care providers, and less frequent colonoscopies and mammograms, and were more likely to smoke and less likely to have a prior diagnosis of basal cell carcinoma. CONCLUSIONS: This study uncovers gaps in healthcare utilization of services among patient groups with cutaneous melanoma as well as possible implications for management of disease progression. Data-driven analyses emphasize the importance of routine clinic visits to dermatologists and/or primary care physicians (PCPs) for early detection and management of cutaneous melanoma. The findings from this study demonstrate that unsupervised ML methodology may serve to define the best candidate patients to benefit from enhanced dermatology/primary care which, in turn, is expected to improve outcomes for cutaneous melanoma.

Clinical, Morphologic, and Molecular Features of Benign and Intermediate-grade Melanocytic Tumors With Activating Mutations in MAP2K1.

Activating mutations in MAP2K1 can be seen in benign and intermediate-grade melanocytic neoplasms with spitzoid morphology. We analyzed the clinical, histopathologic, and genetic features for 16 cases of benign and intermediate-grade melanocytic tumors harboring activating MAP2K1 mutations. We compared them to Spitz neoplasms with characteristic Spitz fusions or HRAS mutation. We also compared the mutational pattern of benign and intermediate-grade MAP2K1 -mutated neoplasms and melanomas with activating MAP2K1 mutations. Among the 16 cases, the favored morphologic diagnosis was Spitz nevus (8/16), atypical Spitz tumors (6/16), and deep penetrating nevus (2/16). The 2 most common architectural patterns seen included a plaque-like silhouette with fibroplasia around the rete reminiscent of a dysplastic nevus (n=7) or a wedge-shaped or nodular pattern with the plexiform arrangement of the nests aggregating around the adnexa or neurovascular bundle (n=8). The cases with dysplastic architecture and spitzoid cytology resembled dysplastic Spitz nevi. Compared with true Spitz neoplasms, MAP2K1 -mutated neoplasms occurred in older age groups and had more frequent pagetosis and a lower average mitotic count. The most common type of mutation in the benign and intermediate-grade cases in the literature involves an in-frame deletion, while, in melanomas, missense mutations are predominant. Benign and intermediate-grade melanocytic neoplasms with activating mutations in MAP2K1 can have morphologic overlap with Spitz neoplasms. A significant proportion of melanomas also have activating MAP2K1 mutations. In-frame deletions are predominantly seen in the benign and intermediate-grade cases, and missense mutations are predominantly seen in melanomas.

Melanoma cells repress Desmoglein 1 in keratinocytes to promote tumor cell migration.

Melanoma is an aggressive cancer typically arising from transformation of melanocytes residing in the basal layer of the epidermis, where they are in direct contact with surrounding keratinocytes. The role of keratinocytes in shaping the melanoma tumor microenvironment remains understudied. We previously showed that temporary loss of the keratinocyte-specific cadherin, Desmoglein 1 (Dsg1), controls paracrine signaling between normal melanocytes and keratinocytes to stimulate the protective tanning response. Here, we provide evidence that melanoma cells hijack this intercellular communication by secreting factors that keep Dsg1 expression low in the surrounding keratinocytes, which in turn generate their own paracrine signals that enhance melanoma spread through CXCL1/CXCR2 signaling. Evidence suggests a model whereby paracrine signaling from melanoma cells increases levels of the transcriptional repressor Slug, and consequently decreases expression of the Dsg1 transcriptional activator Grhl1. Together, these data support the idea that paracrine crosstalk between melanoma cells and keratinocytes resulting in chronic keratinocyte Dsg1 reduction contributes to melanoma cell movement associated with tumor progression.

NONO::TFE3 fusion cutaneous epithelioid and spindle cell tumor: A case series.

The NONO::TFE3 fusion has been described in MiT family translocation renal cell carcinomas as well as extracutaneous perivascular epithelioid cell tumors (PEComas). PEComas are known to express myogenic and melanocytic markers but SOX10 and p63 positivity has never been reported. We report two primary cutaneous tumors that morphologically and molecularly fit PEComas, both harboring the NONO::TFE3 fusion, but with an unusual immunophenotype of SOX10 and p63 positivity. One case was on an 80-year-old male's finger, and the other one was on a 72-year-old female's thigh. Both were well-circumscribed multinodular dermal tumors composed of nests of monotonous epithelioid to spindled cells with pale to vacuolated cytoplasm, some of which were arranged around blood vessels. Both tumors were positive for SOX10, S100, and p63, focally positive for Melan-A, and negative for myogenic markers. There are very little data regarding the molecular findings of primary cutaneous PEComas. While the NONO::TFE3 fusion has been identified in extracutaneous PEComas, it has never been reported in primary cutaneous cases. We believe these cases represent a previously undescribed subtype of cutaneous tumor which shows some immunophenotypic expression of melanocytic markers and we named these cases NONO::TFE3 fusion cutaneous epithelioid and spindle cell tumor. Further, we raise the question of whether this tumor should fall under the rubric of PEComa because of its morphology, partial expression of melanocytic markers, and the presence of the NONO::TFE3 fusion, or whether these tumors represent a separate novel class of tumors since the immunophenotypic expression of SOX10 and p63 is unusual for PEComas.

A reappraisal of the epidemiology of Spitz neoplasms in the molecular era: A retrospective cohort study.

BACKGROUND: Previous studies suggest that Spitz neoplasms occur primarily in younger patients, leading pathologists to shy away from diagnosing a benign Spitz neoplasm in the elderly. With the advent of genomic sequencing, there is a need for reappraisal of the epidemiology of Spitz neoplasms in the modern molecular era. OBJECTIVE: We aim to reassess the epidemiology of Spitz neoplasms incorporating next-generation sequencing. METHODS: We looked at 53,814 non-Spitz neoplasms and 1260 Spitz neoplasms including 286 Spitz neoplasms with next-generation sequencing testing and collected various epidemiologic data. RESULTS: In our general pool of cases, the proportion of Spitz neoplasm cases occurring is relatively the same in each of the first 4 decades of life with a precipitous drop in the fifth decade. In assessing a group of genomically verified cases of Spitz neoplasms, the drop was much less significant and up to 20% of all Spitz neoplasm cases occurred in patients over 50 years of age. LIMITATIONS: Limitations included the number of genetically verified Spitz neoplasm cases available and a possible bias as to which cases undergo genomic testing. CONCLUSION: Genomic verification may allow more confident diagnosis of Spitz neoplasms in patients over 50 years of age and avoid melanoma overdiagnosis.

Agminated presentation of fusion-driven melanocytic neoplasms.

BACKGROUND: The conventionally understood pathogenesis of agminated Spitz nevi includes a mosaic HRAS mutation followed by copy number gains in 11p. However, we have recently observed agminated presentations of fusion-driven melanocytic neoplasms. METHODS: We retrieved cases from our database of benign fusion-induced melanocytic neoplasms with an agminated presentation. Both the primary lesion and the secondary lesion were sequenced. TERT-promoter mutational testing and the melanoma fluorescence in situ hybridization assay were also performed. RESULTS: Three cases were included. Two had a PRKCA fusion (partners ATP2B4 and MPZL1) and one had a ZCCHC8::ROS1 fusion. None of the cases met morphologic or molecular criteria for malignancy. There was no evidence of tumor progression in secondary lesions. The same fusion was identified in the primary and secondary lesions. None of the patients developed evidence of nodal or systemic metastasis. CONCLUSIONS: We present accumulating evidence that fusion-driven melanocytic neoplasms can present with an agminated presentation. The differential diagnosis of an agminated presentation versus a locally recurrent or potentially locally metastatic tumor is critical, and accurate diagnosis has significant prognostic and therapeutic consequences for the patient. As with HRAS mutations, fusion-driven melanocytic tumors may have an agminated presentation.

PRAME Immunohistochemical Expression and TERT Promoter Mutational Analysis as Ancillary Diagnostic Tools for Differentiating Proliferative Nodules From Melanoma Arising in Congenital Nevi.

ABSTRACT: Proliferative nodules (PNs) are benign melanocytic proliferations that typically develop within congenital melanocytic nevi. These tumors have overlapping histological features with melanoma. Ancillary immunohistochemistry and genomic sequencing are often used in diagnostically challenging cases. To assess the utility of preferentially expressed antigen in melanoma (PRAME) immunoreactivity and telomerase reverse transcriptase (TERT) promoter mutation analysis in distinguishing PNs from melanoma arising in congenital nevi cases. Twenty-one PNs and 2 melanomas arising in congenital nevi were immunohistochemically stained with PRAME. Cases with adequate tissue were also assessed for TERT promoter mutations through sequencing studies. The positivity rates in the PN cases were compared with those of the melanomas. Two of 21 PN cases were diffusely positive for PRAME (≥75% of the tumor cells positive). Two of 2 melanomas arising in congenital nevus cases were also diffusely PRAME positive. The difference was statistically significant using a Fisher exact test. None of the tumors harbored TERT promoter mutations. PRAME immunohistochemical marker may have diagnostic value in distinguishing diagnostically challenging PNs from melanoma, but diffuse expression is not specific for melanoma.

Routine imaging guided by a 31-gene expression profile assay results in earlier detection of melanoma with decreased metastatic tumor burden compared to patients without surveillance imaging studies.

Patients with early-stage disease typically have a good prognosis, but still have a risk of recurrence, even with negative sentinel lymph node biopsy (SLNB). This study explores the utility of routine imaging to detect metastases in patients with negative SLNB but high-risk 31 gene expression profile (31-GEP) scores. We retrospectively identified melanoma patients with negative SLNBs. Patients with high-risk GEP results were placed in the experimental group and patients without GEP testing were placed in the control group. Among both cohorts, recurrent melanoma groups were identified. The tumor burden at the time of recurrence and the time to recurrence were compared between experimental group patients with routine imaging and control group patients without imaging schedules. We identified 327 control patients and 307 experimental patients, of which 14.1% versus 20.5% had melanoma recurrence, respectively. Of the patients with recurrent melanoma, those in the experimental group were older (65.75 versus 59.20), had higher Breslow depths (3.72 mm versus 3.31 mm), and had advanced tumor staging (89.5% versus 71.4% of patients presenting clinical stage ≥ II) compared to the control group at primary diagnosis. However, melanoma recurrence was detected earlier (25.50 months versus 35.35 months) in the experimental group at a lower overall tumor burden (73.10 mm versus 27.60 mm). A higher percentage of experimental patients started immunotherapy when offered (76.3% and 67.9%). Patients who received routine imaging after high-risk GEP test scores had an earlier recurrence diagnosis with lower tumor burden, leading to better clinical outcomes.