Gene of the month: BCOR.

BCL-6 transcriptional corepressor () gene is located at Xp11.4 and encodes a protein which is involved in transcriptional repression in association with BCL-6 and epigenetic silencing through polycomb repressive complex 1 (PRC1). mutations are being identified in an increasing number of tumours which are diverse in their anatomical location and clinical setting. Interestingly, these tumours share similar and overlapping histological features, namely small round blue cell morphology and a myxoid background with delicate capillary channels. Clear cell sarcoma of the kidney, primitive myxoid mesenchymal tumour of infancy and central nervous system high-grade neuroepithelial tumour with alteration all share similar internal tandem duplications in the polycomb-group really interesting new gene (RING) finger homolog ubiquitin-likefold discriminator domain of Translocations resulting in fusion with , and have been identified in undifferentiated round cell sarcoma. Subsets of high-grade endometrial stromal sarcoma and ossifying fibromyxoid tumour which have a more aggressive clinical course have been shown to harbour fusions. BCOR immunohistochemistry is an established marker with diagnostic utility.