Broadening the spectrum of SMARCB1-associated malignant tumors: a case of uterine leiomyosarcoma in a patient with schwannomatosis

Schwannomatosis is a tumor predisposition syndrome characterized by development of multiple intracranial, spinal, and peripheral schwannomas. Constitutional alterations in either SMARCB1 or LZTR1 on 22q are responsible of the phenotype. We describe a 34-year-old woman who developed multiple benign peripheral sheath tumors and a uterine leiomyosarcoma. The patient carried a de novo constitutional alteration in exon 8 of SMARCB1, c.1118G > A, which destroyed the splice donor site of intron 8. Two schwannomas and the leiomyosarcoma of the patient retained the SMARCB1 mutation; in addition, the tumors showed loss of the normal chromosome 22. In conclusion, our findings enlarged the spectrum of SMARCB1-predisposing tumors and demonstrated, for the first time, the association of a malignant smooth muscle tumor to schwannomatosis. Therefore, clinicians should definitely be aware that a constitutional SMARCB1 mutation, which mainly predisposes to benign nerve sheath tumors, may also predispose to aggressive neoplasms throughout life, within an unexpected spectrum.