Frequent NFIB-associated Gene Rearrangement in Adenoid Cystic Carcinoma of the Vulva
Adenoid cystic carcinoma is a rare malignant tumor that usually arises in the major and minor salivary glands and other locations containing secretory glands, including the lower female genital tract. Lower female genital tract carcinomas with adenoid cystic differentiation can be subclassified into 2 distinct groups based on the presence or absence of high-risk HPV. Cervical mixed carcinomas with some adenoid cystic differentiation are high-risk HPV-related but pure adenoid cystic carcinomas of vulvar and cervical origin appear to be unrelated to high-risk HPV. Mechanisms by which normal cells give rise to an HPV-unrelated adenoid cystic carcinoma remain largely unknown. Studies demonstrate that chromosomal translocation involving the genes encoding the transcription factors MYB and NFIB functions as a driving force of adenoid cystic carcinomas development regardless of anatomic site. The current study used fluorescence in situ hybridization with 3 different probes including MYB break-apart probe, NFIB break-apart probe, and MYB-NFIB fusion probe to assess for the presence of gene rearrangements in adenoid cystic carcinomas of the vulva. Six (66.7%) of 9 vulvar adenoid cystic carcinomas demonstrated NFIB rearrangement. Of these 6 cases with a disturbed NFIB, only 2 cases (33.3%) were positive for a MYB rearrangement that was also confirmed by a positive MYB-NFIB fusion pattern. NFIB-associated gene rearrangement is a frequent genetic event in vulvar adenoid cystic carcinomas. Chromosome translocations involving NFIB but with an intact MYB indicate the presence of novel oncogenic mechanisms for the development of adenoid cystic carcinomas of the vulva.