In addition, we have identified disease-associated PTEN protein variants with single amino acid substitutions which lack the BA226 or 425A epitopes, making possible the use of these mAb to monitor, in comparison with anti-PTEN mAb targeting other epitopes, the relative expression of pathogenic variants of PTEN in PHTS patients harbouring specific PTEN gene mutations. Here, PTEN is linked to PTEN hamartoma tumor syndrome.