title: Detection of Rare Variant of SS18-SSX1 Fusion Gene and Mutations of Important Cancer-Related Genes in Synovial Sarcoma of the Lip: Gene Analyses of a Case and Literature Review.
abstract: Synovial sarcoma (SS) accounts for 5 to 10% of soft tissue sarcomas; however, intraoral SS is rare. Histopathologically, SS shows a biphasic pattern with epithelial and spindle cell components or a monophasic pattern with only spindle cells. The precise diagnosis of SS, especially at an unusual site, is often a challenge to pathologists and clinical oncologists, because the differential diagnosis of SS includes a broad range of tumors, such as soft tissue sarcomas and carcinomas. In the present case, the patient was a 50-year-old woman who presented with the chief complaint of swelling and a slowly enlarging mass of the lower lip in the mucolabial fold region. The mass was covered with intact mucosa and intraoral examination showed no malignant findings. The clinical diagnosis was a benign tumor and a probable salivary gland tumor. Macroscopically, the excised mass also indicated a benign tumor; however, histopathologic findings suggested the diagnosis of SS. For definitive diagnosis, genetic analyses were performed with conventional polymerase chain reaction and next-generation sequencing. As a result, a rare variant of the SS18-SSX1 fusion transcript, which could not be identified by routine procedures for genetic diagnosis, was detected. In addition, 8 missense mutations of cancer-related genes were confirmed. Detection of the fusion transcript is widely used in the diagnosis of SS; however, reported cases of transcript variants of each fusion gene type are limited. Reports of mutational analysis of cancer-related genes on SS also are rare. The accumulation of rare transcript variants and the cytogenetic characters of SS are suggested to be necessary for assuming a genetic diagnosis of SS.
authors.affiliation: Associate Professor, Division of Anatomical and Cellular Pathology, Department of Pathology, Iwate Medical University, Iwate, Japan. Electronic address: toshi_m@sea.plala.or.jp.
authors.forename: Toshinari
authors.initials: T
authors.lastname: Mikami
authors.affiliation: Professor, Department of Anatomic Pathology, Hirosaki University Graduate School of Medicine, Aomori, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kurose
authors.affiliation: Research Associate, Division of General Dentistry, Eastman Institute for Oral Health, University of Rochester, Rochester, NY.
authors.forename: Fawad
authors.initials: F
authors.lastname: Javed
authors.affiliation: Professor, Division of Anatomical and Cellular Pathology, Department of Pathology, Iwate Medical University, Iwate, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Takeda
mesh_terms: D017931:DNA Primers; D005260:Female; D050939:Gene Fusion; D006801:Humans; D008048:Lip Neoplasms / Q000235:genetics*; D008875:Middle Aged; D020125:Mutation, Missense; D009363:Neoplasm Proteins / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013584:Sarcoma, Synovial / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; C093961:SS18 protein, human; C093962:synovial sarcoma X breakpoint proteins