Uveal melanoma is the most common malignant tumor of the adult eye. Fifty percent of tumors will eventually metastasize, and there are no effective treatments for them. Recent studies of uveal melanoma have identified activating mutations in GNAQ and GNA11, loss-of-function mutations in the tumor suppressor gene BAP1, and recurrent mutations in codon 625 of SF3B1. Previous studies have reported the existence of a higher frequency of GNA11 than GNAQ mutations, frequent BAP1 loss, and rare SF3B1 mutations in metastatic uveal melanoma. We analyzed a cohort of 30 uveal melanoma metastases for the occurrence of GNAQ, GNA11, and SF3B1 mutations, as well as BAP1 loss, and correlated these parameters with clinical and histopathologic features. Most (92%) tumors were composed of cells with an epithelioid or mixed (o100% spindle cells) morphology. Tumor samples composed exclusively of spindle cells were rare (n ¼ 2, 8%). Most tumors showed a moderate to marked degree of nuclear pleomorphism (n ¼ 24, 96%), and contained hyperchromatic, vesicular nuclei with variably conspicuous nucleoli. GNA11 mutations were considerably more frequent than GNAQ mutations (GNA11, GNAQ, and wild-type in 18 (60%), 6 (20%), and 6 (20%) cases, respectively). SF3B1 mutation was found in 1 of 26 tumors (4%), whereas loss of BAP1 expression was present in 13 of 16 tumors (81%). Patients with GNA11-mutant tumors had poorer disease-specific survival (60.0 vs 121.4 months, P ¼ 0.03) and overall survival (50.6 vs 121.4 months, P ¼ 0.03) than those with tumors lacking GNA11 mutations. The survival data, combined with the predominance of GNA11 mutations in metastases, raises the possibility that GNA11-mutant tumors may be associated with a higher risk of metastasis and poorer prognosis than GNAQ-mutant tumors. Further studies of uveal melanoma are required to investigate the functional and prognostic relevance of oncogenic mutations in GNA11 and GNAQ.

The chromosomal region 14q32 contains several imprinted genes, which are expressed either from the paternal (DLK1 and RTL1) or the maternal (MEG3, RTL1as and MEG8) allele only. Imprinted expression of these genes is regulated by two differentially methylated regions (DMRs), the germline DLK1/MEG3 intergenic (IG)-DMR (MEG3/DLK1:IG-DMR) and the somatic MEG3-DMR (MEG3:TSS-DMR), which are methylated on the paternal and unmethylated on the maternal allele. Disruption of imprinting in the 14q32 region results in two clinically distinct imprinting disorders, Temple syndrome (TS14) and Kagami-Ogata syndrome (KOS14). Another DMR with a yet unknown function is located in intron 2 of MEG8 (MEG8-DMR, MEG8:Int2-DMR). In contrast to the IG-DMR and the MEG3-DMR, this somatic DMR is methylated on the maternal chromosome and unmethylated on the paternal chromosome. We have performed extensive methylation analyses by deep bisulfite sequencing of the IG-DMR, MEG3-DMR and MEG8-DMR in different prenatal tissues including amniotic fluid cells and chorionic villi. In addition, we have studied the methylation pattern of the MEG8-DMR in different postnatal tissues. We show that the MEG8-DMR is hypermethylated in each of 13 non-deletion TS14 patients (seven newly identified and six previously published patients), irrespective of the underlying molecular cause, and is always hypomethylated in the four patients with KOS14, who have different deletions not encompassing the MEG8-DMR itself. The size and the extent of the deletions and the resulting methylation pattern suggest that transcription starting from the MEG3 promoter may be necessary to establish the methylation imprint at the MEG8-DMR.

Melanocytic tumors originating in the central nervous system (MT-CNS) are rare tumors that generally have a favorable prognosis, however malignant tumors do occur. Pathogenetically MT-CNS are not well characterized. Similar to uveal melanoma and blue nevi, they frequently harbor activating GNAQ or GNA11 mutations. Rare NRAS mutations have also been reported. Other mutations have not yet been described. We analyzed 19 MT-CNS, 7 uveal melanomas and 19 cutaneous melanomas using a targeted next generation sequencing approach analyzing 29 genes known to be frequently mutated in other melanocytic tumors (in particular uveal and cutaneous melanomas). In concordance with previous studies, cutaneous melanoma samples showed frequent NRAS or BRAF mutations, as well as mutations in other genes (e.g. NF1, RAC1, PIK3CA, ARID1A). Metastasized uveal melanomas exhibited mutations in GNAQ, GNA11 and BAP1. In contrast, MT-CNS almost exclusively demonstrated mutations in GNAQ (71 %) or GNA11 (12 %). Interestingly both GNA11 mutations identified were detected in MT-CNS diagnosed as intermediate grade melanocytomas which also recurred. One of these recurrent cases also harbored an inactivating BAP1 mutation and was found to have lost one copy of chromosome 3. Our findings show that while MT-CNS do have GNAQ or GNA11 mutations, they rarely harbor other recurrent mutations found in uveal or cutaneous melanomas. Considering chromosome 3 and BAP1 loss are robust markers of poor prognosis in uveal melanoma, it will prove interesting to determine whether these genomic alterations are also of prognostic significance in MT-CNS.

7 T gradient-echo sequences provide excellent image contrast of presumed microvasculature and necrosis in astrocytomas.

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