Isolated Langerhans cell histiocytosis of the thyroid: a report of two cases with nuclear imaging-pathologic correlation.

We describe two cases of isolated langerhans cell histiocytosis (LCH) of the thyroid gland, one of which was found in conjunction with an incidental papillary carcinoma. The first case was that of a 43-year-old man who presented with a 1- to 2-cm nodule within the left lobe of the thyroid. Fine-needle aspiration cytology revealed atypical cells with convoluted nuclei in a background of eosinophils and lymphocytes. The findings prompted a recommendation for excision secondary to the high suspicion of a hematologic malignancy. Histologic sections demonstrated LCH in association with a small focus of papillary carcinoma. The second case involved a 43-year-old woman who presented with a 1.8-cm nodule within the right lobe of the thyroid. Fine-needle aspiration in this case demonstrated abundant hemosiderin-laden macrophages, occasional lymphocytes, and a single benign sheet of follicular cells. No eosinophils were seen; however, a single group of atypical histiocytic cells with cleaved nuclei was noted. The nodule was subsequently resected. Histologic examination demonstrated LCH in association with follicular nodular hyperplasia with cystic degeneration. Immunohistochemical studies were performed in both cases, revealing CD1a and S100 immunoreactivity in the Langerhans' cells. Although LCH may occur as a manifestation of systemic disease, its occurrence as an isolated finding in the thyroid is rare. Its occurrence in association with papillary carcinoma of the thyroid is even more uncommon. We present two cases of isolated LCH of the thyroid, one of which was found in association with papillary carcinoma of the thyroid. The cytologic, histologic, immunohistochemical, and radiologic features are described in each case. The ultrastructural findings from the first case are also presented.