Lhermitte–Duclos disease with Cowden disease: Two cases report

• Adult LDD is strongly linked to Cowden disease, necessitating systematic PTEN screening. • Two cases demonstrate LDD with thyroid nodules and trichilemmomas meeting Cowden criteria. • Comprehensive preoperative evaluation is recommended for all adult LDD patients. Lhermitte-Duclos disease (LDD), also known as dysplastic cerebellar gangliocytoma, which is a rare posterior fossa benign tumor, has a possible association with Cowden disease, a rare autosomal dominant disorder caused by germline mutations in the phosphatase and tensin homolog (PTEN) tumor suppressor gene on chromosome 10, with an estimated incidence of 1/200,000–1/250,000. Combined Cowden disease and LDD cases are rarely reported in the literature. Case presentation: We report two male patients with LDD who exhibited the typical “tiger-stripe sign” on imaging. Upon retrospective review after surgery, we found that they also had nodular goiter and extensive facial trichilemmomas. These clinical features met the diagnostic criteria for Cowden disease. LDD in adult patients is highly associated with Cowden disease. Although LDD exhibits characteristics of a benign tumor, given the potential of Cowden disease as a precancerous condition, we recommend initiating a comprehensive preoperative evaluation for all adult patients with LDD.