Glioblastomas, astrocytomas and oligodendrogliomas linked to Lynch syndrome

Muir-Torre syndrome (MTS): An update and approach to diagnosis and management

Muir-Torre syndrome (MTS) is a rare genetic condition that predisposes individuals to skin tumors and visceral malignancies. Because of the potentially aggressive nature of internal malignancies and sebaceous carcinoma, and the tendency to have multiple low-grade visceral cancers, close cancer surveillance is required in individuals and their families with this usually autosomal dominant disorder. Although the majority of MTS is caused by mutations in DNA mismatch repair genes resulting in microsatellite instability, a newly described subtype of MTS does not demonstrate microsatellite instability and may be inherited in an autosomal recessive pattern. In addition, MTS may be unmasked in transplant recipients taking specific immunosuppressant drugs or other immunosuppressed patients. Neoplasms may be subject to immunohistochemistry or both immunohistochemistry and genetic testing to confirm the diagnosis of MTS. Here, we offer an update and an approach to the diagnosis and management of MTS with a particular emphasis on the role of immunohistochemistry and genetic testing.

ATRX immunostaining predicts IDH and H3F3A status in gliomas

Gliomas are the most frequent intraaxial CNS neoplasms with a heterogeneous molecular background. Recent studies on diffuse gliomas have shown frequent alterations in the genes involved in chromatin remodelling pathways such as α-thalassemia/mental-retardation-syndrome-X-linked gene (ATRX). Yet, the reliability of ATRX in predicting isocitrate dehydrogenase (IDH) and H3 histone, family 3A (H3F3A) mutations in gliomas, is unclear.We analysed the ATRX expression status by immunohistochemistry, in a large series of 1064 gliomas and analysed the results in correlation to IDH, H3F3A and loss of heterozygosity (LOH) 1p/19q status in these tumors. We also investigated the prognostic potential of ATRX concerning the clinical outcome of patients with diffuse gliomas.According to our results, loss of nuclear ATRX expression was accompanied with an astrocytic tumor lineage and a younger age of onset. ATRX loss in astrocytomas was also strongly associated with IDH1/2 and H3F3A mutation (p < 0.0001). Among 196 glial tumors with nuclear ATRX loss, 173 (89 %) had an IDH1 or IDH2 mutation. Among the remaining 23 cases (11 %) with ATRX loss and IDH wild type status, 7 cases had a H3F3A G34R mutation (3 %) and 2 cases had a H3F3A K27M mutation (1 %). ATRX retention in IDH1/2 mutant tumors was strongly associated with LOH 1p/19q and oligodendroglioma histology (p < 0.0001). We also confirmed the significant prognostic role of ATRX. Diffuse gliomas with ATRX loss (n = 137, median 1413 days, 95 % CI: 1065-1860 days) revealed a significantly better clinical outcome compared with tumors with ATRX retention (n = 335, median: 609, 95 % CI: 539-760 days, HR = 1.81, p < 0.0001).In conclusion, ATRX is a potential marker for prediction of IDH/H3F3A mutations and substratification of diffuse gliomas into survival relevant tumor groups. Such classification is of great importance for further clinical decision making especially concerning the therapeutic options available for diffuse gliomas.

Association of MSH6 mutation with glioma susceptibility, drug resistance and progression

MutS homolog 6 (MSH6) is one of the mismatch repair proteins and is encoded by the MSH6 gene, which is located on chromosome 2 and is 23,806 bp in length, including 10 exons and 83 untranslated regions. The MSH6 protein consists of 1,358 amino acid residues and forms a heterodimer with another mismatch repair protein, MSH2. The MSH2-MSH6 heterodimeric complex is able to recognize base-base substitution and single-base insertion/deletion mismatches. Germline mutations of MSH6 lead to high susceptibility to glioma, as well as a number of benign or malignant tumors in other organs. However, somatic MSH6 mutations are not associated with susceptibility to glioma. Somatic MSH6 mutations usually follow temozolomide treatment and result in resistance to temozolomide. Subsequently, MSH6 mutations cause a hypermutation in the glioma cell genome, which may accelerate tumor progression.