When a Lab Stays Silent: A Missed Mosaic Variant and a Four-Year Diagnostic Odyssey
2026
A 10-year-old girl with bilateral vestibular schwannomas had a striking family history: a mother with a childhood brain tumor, multiple relatives with breast and ovarian cancer. Her genetic counselor ordered a comprehensive panel from a well-known lab. The result was negative. A second lab’s targeted analysis was also negative. Four years later — after the child developed spinal meningiomas — whole-genome sequencing finally revealed the truth: a mosaic NF2 variant that the first lab had detected but never reported.
My Gene Counsel CEO Ellen Matloff weighs in on what the lab should have done differently, why mosaic variants create unique challenges for families and clinicians, and what this case reveals about the hidden costs of diagnostic odysseys — and the growing case for upfront WGS in pediatric oncology.