TRK Protein Expression in Merkel Cell Carcinoma Is Not Caused by NTRK Fusions.

Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous malignant tumor with neuroendocrine differentiation, with a rapidly growing incidence rate, high risk of recurrence, and aggressive behavior. The available therapeutic options for advanced disease are limited and there is a pressing need for new treatments. Tumors harboring fusions involving one of the neurotrophin receptor tyrosine kinase (NTRK) genes are now actionable with targeted inhibitors. NTRK-fused genes have been identified in neuroendocrine tumors of other sites; thus, a series of 76 MCCs were firstly analyzed with pan-TRK immunohistochemistry and the positive ones with real-time RT-PCR, RNA-based NGS, and FISH to detect the eventual underlying gene fusion. Despite 34 MCCs showing pan-TRK expression, NTRK fusions were not found in any cases. As in other tumors with neural differentiation, TRK expression seems to be physiological and not caused by gene fusions.

The Molecular Landscape of Primary Acral Melanoma: A Multicenter Study of the Italian Melanoma Intergroup (IMI).

Acral melanoma (AM) is a rare and aggressive subtype of melanoma affecting the palms, soles, and nail apparatus with similar incidence among different ethnicities. AM is unrelated to ultraviolet radiation and has a low mutation burden but frequent chromosomal rearrangements and gene amplifications. Next generation sequencing of 33 genes and somatic copy number variation (CNV) analysis with genome-wide single nucleotide polymorphism arrays were performed in order to molecularly characterize 48 primary AMs of Italian patients in association with clinicopathological and prognostic features. BRAF was the most commonly mutated gene, followed by NRAS and TP53, whereas TERT promoter, KIT, and ARID1A were less frequently mutated. Gains and losses were recurrently found in the 1q, 6p, 7, 8q, 20 and 22 chromosomes involving PREX2, RAC1, KMT2C, BRAF, CCND1, TERT, and AKT3 genes, and in the 6q, 9, 10, 11q and 16q chromosomes including CDKN2A, PTEN, and ADAMTS18 genes, respectively. This study confirmed the variety of gene mutations and the high load of CNV in primary AM. Some genomic alterations were associated with histologic prognostic features. BRAF mutations, found with a higher rate than previously reported, correlated with a low Breslow thickness, low mitotic count, low CNV of the AMs, and with early-stage of disease.

Prevalence of ALK gene alterations among the spectrum of plexiform spitzoid lesions.

BACKGROUND: ALK receptor tyrosine kinase gene (ALK) rearrangements have been described in spitzoid lesions with a plexiform growth pattern. OBJECTIVE: To investigate the prevalence of ALK alterations in a large series of spitzoid lesions. METHODS: ALK immunohistochemical and fluorescence in situ hybridization analyses of 78 spitzoid plexiform lesions including 41 Spitz nevi, 29 atypical Spitz tumors (ASTs), and 8 spitzoid melanomas. RESULTS: ALK immunohistochemical staining was observed in 14.6% of Spitz nevi (6 of 41) and 13.8% of ASTs (4 of 29); the spitzoid melanomas were ALK negative. Fluorescence in situ hybridization confirmed ALK translocation in 9 cases and amplification in 1 case. In 2 of the translocated cases it was possible to determine the fusion partner gene (ie, tropomyosin 3 gene [TPM3] or dynactin 1 gene [DCTN1]). Of the 4 cases of AST examined, 2 carried the B-Raf proto-oncogene, serine/threonine kinase gene (BRAF) V600E mutation. The 10 patients had a mean age of 18.7 years (range, 1-39) and a female predominance (female-to-male ratio, 7:3). Seven lesions arose on the extremities; the 2 lesions occurring in infants were located on the face. The lesions' mean diameter was 6.2 mm (range, 3-13), and their mean Breslow thickness was 1.83 mm (range, 0.6-3.6). The results of sentinel node biopsy were negative in 2 ASTs. LIMITATIONS: BRAF status was tested in only 4 of 10 samples because of the limited amount of material. CONCLUSION: ALK alterations characterize a significant subset of spitzoid lesions.

Extraskeletal Myxoid Chondrosarcoma of the Foot Clinically Mimicking Plantar Fibromatosis.

Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft tissue sarcoma usually presenting in proximal extremities of middle-aged men. The authors discuss a unique case of EMC, localized in the plantar foot of a 76-year-old woman, clinically suspected as plantar fibromatosis. It is important to avoid misdiagnosis of EMC because of their propensity for late recurrence and their metastatic potential.

TERT Promoter Mutations Differently Correlate with the Clinical Outcome of MAPK Inhibitor-Treated Melanoma Patients.

Resistance is a major challenge in the management of mitogen-activated protein kinase inhibitor (MAPKi)-treated metastatic melanoma. Tumor genetic alterations can cause MAPK pathway reactivation, leading to lack of response and poor outcome. Characterization of the mutational profile in patients with melanoma might be crucial for patient-tailored treatment choices. Mutations in the promoter region of the telomerase reverse transcriptase gene (TERTprom) lead to increased TERT expression and telomerase activity and are frequent in BRAFV600 mutant melanoma. Reportedly, TERTprom, and BRAFV600 mutations cooperate in driving cancer progression and aggressiveness. We evaluated the effect of the TERTprom status on the clinical outcome in 97 MAPKi-treated melanoma patients. We observed that patients with the c.-146C > T mutation showed a significantly worse progression-free survival (PFS) compared to those carrying the c.-124C > T mutation and a two-fold increased risk of progression (median 5.4 vs. 9.5 months; hazard ratio (HR) 1.9; 95% confidence interval (CI) 1.2-3.2; p = 0.013). This trend was also observed for the overall survival (OS); melanoma patients with the c.-146C > T mutation showed a poorer prognosis compared to those with the c.-124C > T mutation (median 13.3 vs. 25.5 months; HR 1.9, 95% CI 1.1-3.3, p = 0.023). Our results disclose a different correlation of the two TERTprom mutations with MAPKi-treated melanoma patient outcome, highlighting a different impact of the pathway blockade.

Periostin and Epithelial-Mesenchymal Transition Score as Novel Prognostic Markers for Leiomyosarcoma, Myxofibrosarcoma, and Undifferentiated Pleomorphic Sarcoma.

PURPOSE: Interpatient clinical variability in soft-tissue sarcomas (STS) highlights the need for novel prognostic markers supporting patient risk stratification. As sarcomas might exhibit a more mesenchymal or a more epithelial state, we focused on epithelial-mesenchymal and mesenchymal-epithelial transitions (EMT/MET) for prognostic clues, and selected three histotypes with variable aggressiveness. EXPERIMENTAL DESIGN: The expression of EMT/MET-related factors was measured by qRT-PCR in 55 tumor samples from patients with leiomyosarcoma, myxofibrosarcoma, or undifferentiated pleomorphic sarcoma. The identified marker was further evaluated by IHC in 31 leiomyosarcomas and by measuring its circulating levels in 67 patients. The prognostic value of a sarcoma-tailored EMT score was analyzed. Epirubicin chemosensitivity and migration were studied in primary STS cultures. Associations with overall survival (OS) were assessed using Kaplan-Meier and Cox regression methods. RESULTS: High expression of periostin, a mesenchymal matricellular protein, in sarcoma tissues (P = 0.0024), its high stromal accumulation in leiomyosarcomas (P = 0.0075), and increased circulation (>20 ng/mL, P = 0.0008) were associated with reduced OS. High periostin expression [HR 2.9; 95% confidence interval (CI), 1.3-6.9; P = 0.0134] and circulation (HR 2.6; 95% CI, 1.3-5.1; P = 0.0086), and a mesenchymal EMT score (mesenchymal vs. transitioning; HR, 5.2; 95% CI, 2.1-13.0, P = 0.0005) were associated with increased risk in multivariable models. An intrinsic or induced mesenchymal state enhanced chemoresistance and migration in sarcoma cell lines. CONCLUSIONS: Although limited to a pilot study, these findings suggest that periostin might contribute prognostic information in the three studied STS histotypes. Moreover, a transitioning EMT score measured in the tumor might predict a less active and a more chemosensitive disease.

BRAF Gene Copy Number and Mutant Allele Frequency Correlate with Time to Progression in Metastatic Melanoma Patients Treated with MAPK Inhibitors.

Metastatic melanoma is characterized by complex genomic alterations, including a high rate of mutations in driver genes and widespread deletions and amplifications encompassing various chromosome regions. Among them, chromosome 7 is frequently gained in BRAF-mutant melanoma, inducing a mutant allele-specific imbalance. Although BRAF amplification is a known mechanism of acquired resistance to therapy with MAPK inhibitors, it is still unclear if BRAF copy-number variation and BRAF mutant allele imbalance at baseline can be associated with response to treatment. In this study, we used a multimodal approach to assess BRAF copy number and mutant allele frequency in pretreatment melanoma samples from 46 patients who received MAPK inhibitor-based therapy, and we analyzed the association with progression-free survival. We found that 65% patients displayed BRAF gains, often supported by chromosome 7 polysomy. In addition, we observed that 64% patients had a balanced BRAF-mutant/wild-type allele ratio, whereas 14% and 23% patients had low and high BRAF mutant allele frequency, respectively. Notably, a significantly higher risk of progression was observed in patients with a diploid BRAF status versus those with BRAF gains [HR, 2.86; 95% confidence interval (CI), 1.29-6.35; P = 0.01] and in patients with low percentage versus those with a balanced BRAF mutant allele percentage (HR, 4.54; 95% CI, 1.33-15.53; P = 0.016). Our data suggest that quantitative analysis of the BRAF gene could be useful to select the melanoma patients who are most likely to benefit from therapy with MAPK inhibitors. Mol Cancer Ther; 17(6); 1332-40. ©2018 AACR.