Dysplastic gangliocytoma (Lhermitte-Duclos disease [LDD]) typically presents as a PTEN (phosphatase and tensin homolog)-positive, insidious unilateral mass of the cerebellar cortex.
The diagnosis of Cowden syndrome with PTEN gene mutation, linked to higher risk of neoplasia and occurrence of hamartomatous lesions characteristic of the Lhermitte-Duclos disease (LDD), was confirmed by genetic investigation.
Lhermitte-Duclos disease is a rare hamartomatous tumor of the cerebellum resulting from a mutation in the phosphatase and tensin homolog (PTEN) gene: it has been reported in fewer than 10 infants.
At 6 months before his death, the patient complained of hoarseness and dysphagia, and clinical whole-body examinations revealed advanced lung adenocarcinoma (T4N2M1b, Stage IV), multiple skin verrucas, gastrointestinal polyposis, goiters, and cerebellar dysplastic gangliocytoma (Lhermitte-Duclos disease), while PTEN gene mutation was detected in his serum.
A PTEN mutation, c.1003C>T p.(Arg335Ter), was subsequently identified as the cause of Cowden syndrome in another family member (a nephew) with dysplastic gangliocytoma of the cerebellum (Lhermitte-Duclos disease), and genetic testing in the proband's daughter indicated that he was an obligate carrier of the mutation.
In addition, the differential PTEN mutation status with corresponding LDD phenotypes suggests a potential correlation between germline or somatic mutation and coexisting LDD/CS or isolated LDD, respectively.
Mutations in the PTEN gene are associated with a broad spectrum of disorders, including Cowden syndrome (CS), Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Lhermitte-Duclos disease.
This case of Lhermitte-Duclos disease associated with paraspinal AVF and mutation of the PTEN gene suggests a relationship between Lhermitte-Duclos disease and Cowden disease.
Immunohistochemical analysis showed high levels of phospho-AKT and phospho-S6 in the large ganglionic cells forming the lesions, indicating activation of the PTEN/AKT/mTOR pathway and suggesting a central role for mTOR in the pathogenesis of LDD.
It remains unclear whether all cases of LDD, even without features of CS, are caused by germline PTEN mutation and whether somatic PTEN mutation occurs in sporadic LDD.
PTEN is a tumor suppressor gene mutated in many human sporadic cancers and in hereditary cancer syndromes such as Cowden disease, Bannayan-Zonana syndrome and Lhermitte-Duclos disease.
A heterozygous frameshift mutation of the PTEN/MMAC1 gene in a patient with Lhermitte-Duclos disease - only the mutated allele was expressed in the cerebellar tumor.
A candidate tumour suppressor gene, PTEN, has recently been identified within chromosome 10q23, the locus of the Cowden syndrome/Lhermitte Duclos disease susceptibility gene.