Lhermitte-Duclos is a posterior fossa dysplasia that mimicks a space-occupying lesion, comprised of a complex hamartoma or malformation. The cerebellar folia appear hyperplastic. Histological appearace is of cellular disorganization, hypertrophied granular neurons, and axonal hypermyelination. MRI shows laminated increased signal on T2 weighted imaging.
This disease can be associated with Cowden syndrome, an autosomal dominant syndrome (mutation in the PTEN tumour suppressor gene on chromosome 10q) causing multiple hamartomatous neoplasms of the skin and mucosa, GI tract, bones, CNS, eyes, and genitourinary tract, as well as increased risk for some cancers especially breast and thyroid cancer. Macrocephaly and mental retardation is also seen.