Endocrine Abstracts

Introduction: Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous malignancy, affecting predominantly caucasian and older individuals (slight male predominance). This neoplasm is associated with a high risk of local recurrence and regional lymph node involvement. Distant metastases are less frequent; they were described in liver, bone, CNS, skin, lung and spleen. The authors describe a clinical case of Merkel cell carcinoma with a single metastasis in a thyroid nodule.

Clinical case: A 53-year-old caucasian female was submitted to excision of a rapid growing nodule on the internal face of left lower limb. Hystologic examination showed a Merkel cell carcinoma, with 2.5×2.5 cm and positive margins. Additionally, she underwent a thyroid sonography that revealed a left lobe nodule (4×3.2×2 cm) and a small one in right lobe (1.2 cm). Admitted to our hospital, MR scan showed extensive persistent disease in lower limb. 18F-FDG PET showed fixation only in the left lower limb. FNA biopsy of the largest thyroid nodule revealed benign result – colloid. Patient underwent regional hyperthermic perfusion with melfalan and TNFα, and then tumoral lesion excision and plasty. Three years later, she complained of cervical discomfort. Cervical sonography showed thyroid nodule growing, FNA biopsy didn’t result in a conclusive diagnosis. Patient was soon after submitted to total thyroidectomy, revealing a Merkel cell carcinoma metastasis in the thyroid nodule (with 6.5 cm) with gland capsule and soft tissues invasion; a right papillary microcarcinoma (0.1 cm) was also found. Repeated 18F-FDG PET suggested left lower limb recurrence, without other metastases. She was submitted to cervical radiotherapy.

Conclusions: This clinical case describes a Merkel cell carcinoma with a single thyroid metastasis in a previously known nodule with a benign result in FNA biopsy. In oncologic patients, thyroid secondary involvement is an important differential diagnosis in initial evaluation and follow-up of thyroid nodules.