Papillary thyroid carcinoma in Peutz-Jeghers syndrome.

BACKGROUND: Peutz-Jeghers syndrome (PJS) is a rare dominantly inherited disease characterized by the association of gastrointestinal hamartomatous polyposis, mucocutaneous hyperpigmentation, and increased risk of cancer at different target organs. Its occurrence with differentiated thyroid cancer, particularly papillary thyroid carcinoma (PTC), even if rare, has been described.
SUMMARY: We here present a case of PTC observed in a PJS patient and a review of the literature aiming at discussing the utility of thyroid surveillance in the management of these patients. A 22-year-old woman presenting with hyperpigmented lesions of the lips and hamartomatous polyps in the stomach, duodenum, jejunum, and ileum, leading to the suspicion of PJS, was submitted to genetic analysis. Mutation scanning of the Liver Kinase B1 (LKB1) gene identified the presence of the truncating mutation E265X, thus confirming the clinical diagnosis. Beside the endoscopic, radiologic, and echographic evaluations required by the standard surveillance guidelines, the patient had a neck ultrasound (US), which showed a 5×4×6 mm hypoechoic nodule in the right thyroid lobe. The nodule contained microcalcifications and a perinodular vascular pattern. The cytological preparations derived from US-guided fine-needle aspiration biopsy of the nodule demonstrated the presence of PTC. The patient underwent a video-assisted total thyroidectomy and the histological examination revealed a follicular variant of papillary microcarcinoma. Radioactive iodine therapy was not performed because of the small size of the lesion. The patient was started on levothyroxine therapy to keep the serum thyrotropin levels suppressed. Both the sequencing and the multiplex ligation-dependent probe amplification analysis could not identify any LKB1 mutation in the tumor specimen, and the methylation-specific polymerase chain reaction assay excluded hypermethylation of the LKB1 promoter as the mechanism of inactivation for the remaining normal allele in the tumor.
CONCLUSIONS: Although other mechanisms of LKB1 silencing may be responsible for its inactivation in the thyroid cancer, we cannot rule out that the occurrence of thyroid carcinoma could be a coincidental finding in this patient. However, the case here presented suggests that US of the thyroid could possibly become an integral part of the evaluation and the follow-up program adopted for PJS patients.