TERT promoter mutations in sinonasal malignant melanoma: a study of 49 cases.

Sinonasal malignant melanoma (SNMM) comprises less than 1% of all melanomas and is located in the nasal cavity and the paranasal sinuses. The majority of SNMMs have unknown underlying oncogenic driver mutations. The recent identification of a high frequency of driver mutations in the promoter of the telomerase reverse transcriptase (TERT) gene in cutaneous melanoma led us to investigate whether these mutations also occur in SNMM. Our aim was to determine the TERT promoter mutation frequencies in primary SNMMs. Laser capture microdissection and manual dissection were used to isolate tumour cells from 49 formalin-fixed paraffin-embedded tissues. The tumours were screened for TERT promoter mutations by direct Sanger sequencing. Information on NRAS, BRAF and KIT mutation was available from an earlier study. Overall, 8% (4/49) of SNMMs harboured TERT promoter mutations. One of these mutated tumours had a coexistent NRAS mutation and one had a BRAF mutation. Our findings show that TERT promoter mutations are present in a moderate proportion of SNMM. No conclusion can be drawn on their potential influence on the clinical outcome or tumour progression.

BRAFV600E protein expression in primary cutaneous malignant melanomas and paired metastases.

IMPORTANCE: BRAFV600E mutations are present in approximately 50% of cutaneous malignant melanomas (CMMs). The use of BRAFV600E mutation-specific monoclonal antibody VE1 immunohistochemical analysis may facilitate rapid detection of BRAFV600E mutations in CMMs and demonstrate heterogeneity among tumors. OBJECTIVES: To characterize the pattern of BRAFV600E protein expression in primary CMMs with matched metastases and to analyze the use of VE1 immunohistochemical analysis in clinical practice using formalin-fixed, paraffin-embedded tumor tissue. DESIGN, SETTING, AND PARTICIPANTS: In this retrospective cohort study performed at Karolinska University Hospital from September 2012 to September 2013, we examined CMMs (124 primary tumors and 76 metastases) with VE1 immunohistochemical analysis, and results were compared with DNA mutation analyses. MAIN OUTCOMES AND MEASURES: Determination of intratumoral and intertumoral heterogeneity as well as the sensitivity and specificity of VE1 immunohistochemical analysis. RESULTS: Positive staining results with the VE1 antibody were detected in 94 of 200 tumors (47.0%). In general, VE1 staining was homogeneous. However, VE1 staining intensity varied among the primary tumors and corresponding metastases in 63 of 135 tumors (46.7%), but a change of mutational status based on DNA analysis was found in only 4 matched tumors (3.0%). Discordant findings between DNA mutation analysis and immunohistochemical analysis were observed in 12 tumors. The overall sensitivity and specificity of VE1 immunohistochemical analysis were 96.7% and 94.5%, respectively. A comparable sensitivity was obtained for primary and metastatic CMMs. The specificity was lower among primary CMMs (92.4%) compared with metastases (98.0%). CONCLUSIONS AND RELEVANCE: We found VE1 immunohistochemical analysis to be a useful and rapid assay for BRAFV600E mutations that may contribute to the detection of intratumoral and intertumoral heterogenetic subclones. Tumors with positive results, including strong staining, should be expedited for confirmatory BRAF mutation testing. If this test result is negative, a false-negative result of the mutation analysis should be considered. Validation of VE1 immunohistochemical analysis in clinical practice is needed.

KIT, NRAS, BRAF and PTEN mutations in a sample of Swedish patients with acral lentiginous melanoma.

BACKGROUND: Acral lentiginous melanoma (ALM) accounts for <10% of all melanomas in Caucasians. Although the involvement of KIT, NRAS and BRAF mutations is well known in ALM, the impact of these mutations on clinicopathological features has not been established. OBJECTIVE: To define the KIT, NRAS, BRAF and PTEN mutation frequencies in Swedish patients with ALM and to evaluate the impact of mutation status on patient and tumor characteristics. METHODS: Tumor cells were microdissected from 88 primary ALMs and 16 paired metastases and analyzed for KIT, NRAS and BRAF mutations. A subset of 25 ALMs was also evaluated for PTEN mutations. RESULTS: BRAF mutations were identified in 17% of the primary ALMs. Both NRAS and KIT mutations were found at a similar frequency of 15%. Only one of the ALMs that were screened for PTEN harbored a mutation (4%). The KIT, NRAS and BRAF mutation status in paired primary and metastatic ALMs was identical. Patients with BRAF mutated tumors were significantly younger (57 years) than those with BRAF wild-type tumors (73 years, p=0.028). BRAF mutations were significantly more common in females (p=0.011) and more often found in tumors located on the feet (p=0.039). Anatomical site was an independent prognostic factor for overall survival; patients with ALMs on the hands or under fingernails had a better prognosis than those with tumors on the feet or under toenails (p=0.025). CONCLUSION: Our results confirm the presence of KIT, NRAS and BRAF mutations in ALM and provide evidence that mutations in these genes occur at similar frequencies. Our results also show that PTEN is mutated in a small subset of ALM tumors.