Lymph node metastasis from undiagnosed occult papillary thyroid cancer

Abstract

To the Editor A 57-year-old woman was referred to our Endocrine Unit 3 years after she underwent total thyroidectomy for a large non-toxic multinodular goiter with tracheal deviation. At that time histology was negative for malignancy. She had no family history of thyroid disease. At the time of our observation no palpable neck mass was present, but neck ultrasound imaging study revealed a left lateral solid cervical mass (8 9 13 9 14 mm), with features of a lymph node, strongly hypoechoic, lacking in homogeneity, containing several microcalcifications and lack of visibility of the hilum (Fig. 1). The patient gave informed consent to the study and US-FNAB of this mass with thyroglobulin assay in the wash-out liquid were performed. Thyroglobulin (Tg) value of[30.000 ng/ml in the wash-out liquid of the needle and the presence of epithelial follicular cells in the specimen suggested the presence of proliferating thyroid cells [1, 2]. The patient was then submitted to a modified neck dissection. At pathology, neck mass resulted a lymphatic metastasis from occult classic papillary thyroid carcinoma (PTC) because of the presence of lymphatic tissue partially substituted by atypical thyroid cells, with nuclear grooves and ground glass cytoplasma. After surgery the patient received a therapeutic I dose (3,700 Mbq) using the thyroid hormone withdrawal method. In this hypothyroid protocol, levothyroxine treatment was withdrawn for 4 weeks, while triiodothyroxine was given for 2 weeks and then withdrawn for 2 weeks. Serum thyrotropin (TSH) and thyroglobulin (Tg) were then measured. TSH levels were 120 mcUI/ml and Tg was \1 ng/ml. The whole body scan (WBS) after therapy showed only minimal thyroid bed uptake. She is actually on therapy with L-tiroxine at the dose of 900 mcg/week, with TSH 0.5 mcUI/ml, Tg \ 0.2 ng/ml and TgAb \ 10 UI/ml. In this case, neck ultrasound study revealed a loco-regional metastasis from a nodule with no previously evidence of malignancy. This rare event could be the consequence of the presence of a focus of papillary microcarcinoma (microPTC) undiagnosed because of goiter dimension and multiple nodules presence. Papillary thyroid microcarcinomas (PTCs) are found in approximatively in 6–36 % of the population at autopsy. Only fewer than 2 % of microPTCs come to clinical attention [3]. Despite the very low mortality rates, locoregional recurrence is a common clinical problem. Some microPTCs have lymph node metastasis (16–64 %) and multiple tumor formation (23–33 %) at presentation, which are both associated with a less favorable outcome, including distant metastases and increased mortality [3]. In this case, pathological revision of thyroid did not found any focus of carcinoma. This event was reported in 0.17 % of patients previously diagnosed as affected from benign nodular goiter [4]. In this cases a nodular goiter previously diagnosed as non-malignant, after showed a malignant behavior. This was described in rare macrofollicular variant of PTC and in some rare lesions with nuclei less clear than those of conventional papillary carcinoma [4]. In our case, the lesion was described as lymph node metastasis from a classic PTC. We cannot exclude that thyroid microcarcinoma may have developed subsequently on the small thyroid remnant. For this reason, we decided to submit the patient to radioiodine ablation. In 2009, ATA recommended (recommendation 44) periodic serum thyroglobulin assay and neck ultrasonography during followup of patients with thyroid cancers managed with subtotal A. Carbone P. Bellitti R. Bruno (&) Unita Operativa Complessa di Endocrinologia, Ospedale di Tinchi, Matera, Italy e-mail: roccobruno1@virgilio.it