Human gene LOC100505644 uncharacterized LOC100505644 [Homo sapiens] (Entrez Gene ID 100505644) is abundantly expressed in tumors but weakly expressed in few normal tissues. Till now the function of this gene remains unknown. Here we identified the chromosomal borders of the transcribed region and the major splice form of the LOC100505644-specific transcript. We characterised the major regulatory motifs of the gene and its splice sites. Analysis of the secondary structure of the major transcript variant revealed a hairpin-like structure characteristic for precursor microRNAs. Comparative genomic analysis of the locus showed that it originated in primates de novo. Taken together, our data indicate that human gene LOC100505644 encodes some non-protein coding RNA, likely a microRNA. It was assigned a gene symbol ELFN1-AS1 (ELFN1 antisense RNA 1 (non-protein coding)). This gene combines features of evolutionary novelty and predominant expression in tumors.