FOXL2 Mutation (C402G) Analysis by PCR and Pyrosequencing
An aid in the diagnosis of adult granulosa cell tumor
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Granulosa cell tumor (GCT) represents approximately 5% to 10% of all ovarian malignancies and is the most common type of malignant ovarian sex-cord stromal tumor. The majority of patients with GCT (95%) are adults and 5% are juveniles. The histopathological diagnosis of GCT is challenging. Forkhead box L2 (FOXL2) gene is involved in ovarian development and function. The FOXL2 gene point mutation 402C>G in exon 1 (C134W) was reported in the majority of adult GCT (>90%), 5% to 10% of thecomas (tumors closely related to GCT) and <10% of juvenile GCT cases, but not in other ovarian tumors. Detection of FOXL2 mutation aids in the clinical diagnosis of adult GCT.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
The presence of Forkhead box L2 (FOXL2) mutation 402C>G supports the diagnosis of granulosa cell tumor (GCT), but does not rule out the diagnosis of ovarian thecomas (5%-10%). The presence of wild-type FOXL2 does not rule-out the diagnosis of GCT.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Reliable results are dependent on adequate specimen collection and processing. This test has been validated on formalin-fixed, paraffin-embedded tissues; other types of fixatives are discouraged. Improper treatment of tissues, such as decalcification, may cause PCR failure. False-negative results may occur in heterozygous tumor specimens when tumor cells comprise <40% of the cell population. Tumor cells are routinely enriched by macrodissection to avoid false-negative results.
Clinical diagnosis or therapy should not be based solely on this assay. The results should be considered in conjunction with clinical information, histologic evaluation, and additional diagnostic tests.
The Forkhead box L2 (FOXL2) mutation was tested by PCR and pyrosequencing in 102 formalin-fixed, paraffin-embedded (FFPE) tissues, including 53 granulosa cell tumors (GCT) and 49 other non-GCT tissues. Using pathological diagnoses as references, the FOXL2 mutation pyrosequencing test demonstrated the following characteristics: clinical sensitivity (66%), clinical specificity (93.9%), positive predict value (92.1%), and negative predict value (71.9%). The clinical sensitivity was significantly different in GCT subtypes: regular GCT (87%), GCT-diffuse type (66.6%), and GCT with prominent fibrothecomatous component (33.3%). The pyrosequencing results were confirmed by conventional PCR and direct sequencing in all cases.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Shah SP, Kobel M, Senz J, et al: Mutation of FOXL2 in granulosa-cell tumors of the ovary. N Engl J Med 2009;360:2719-2729
2. Kim MS, Hur SY, Yoo NJ, et al: Mutational analysis of FOXL2 codon 134 in granulosa cell tumour of ovary and other human cancers. J Pathol 2010;221:147-152
3. Schrader KA, Gorbatcheva B, Senz J, et al: The specificity of the FOXL2 c.402C->G somatic mutation: a survey of solid tumors. PLoS One 2009 Nov 24;4(11):e7988
4. Benayoun BA, Kalfa N, Sultan C, et al: The forkhead factor FOXL2: a novel tumor suppressor? Biochim Biophys Acta 2010;1805:1-5