[Genomic techniques used in uveal melanoma: a literature review]

Choroidal biopsies; a review and optimised approach

The majority of choroidal tumours are diagnosed accurately with clinical examination and the additional data obtained from non-invasive imaging techniques. Choroidal biopsies may be undertaken for diagnostic clarity in cases such as small melanocytic or indeterminate lesions, identifying the primary tumour in the case of choroidal metastases or the subclassification of rarer conditions such as uveal lymphoma. There is however an increasing use of biopsy techniques for prognostication in uveal melanoma. This review explores the main indications and surgical techniques for tumour acquisition, and the optimised approach utilised by the current authors to improve successful yield for histological and genetic analysis.

Molecular pathology of uveal melanoma

Like other cancers, uveal melanomas (UM) are characterised by an uncontrolled, clonal, cellular proliferation, occurring as a result of numerous genetic, and epigenetic aberrations. Signalling pathways known to be disrupted in UM include: (1) the retinoblastoma pathway, probably as a result of cyclin D1 overexpression; p53 signalling, possibly as a consequence of MDM2 overexpression; and the P13K/AKT and mitogen-activated protein kinase/extracellular signal-related kinase pathway pathways that are disturbed as a result of PTEN and GNAQ/11 mutations, respectively. Characteristic chromosomal abnormalities are common and include 6p gain, associated with a good prognosis, as well as 1p loss, 3 loss, and 8q gain, which correlate with high mortality. These are identified by techniques such as fluorescence in situ hybridisation, comparative genomic hybridisation, microsatellite analysis, multiplex ligation-dependent probe amplification, and single-nucleotide polymorphisms. UM can also be categorised by their gene expression profiles as class 1 or class 2, the latter correlating with poor survival, as do BRCA1-associated protein-1 (BAP1) inactivating mutations. Genetic testing of UM has enhanced prognostication, especially when results are integrated with histological and clinical data. The identification of abnormal signalling pathways, genes and proteins in UM opens the way for target-based therapies, improving prospects for conserving vision and prolonging life.