Langerhans cell histiocytosis of the thyroid gland

Objectives: A case is reported in which Langerhans cell histiocytosis was found in the thyroid gland. Although the thyroid gland is frequently affected with multiple common diseases, a search of the English language literature suggests that Langerhans cell histiocytosis in the thyroid gland is rarely reported. Study Design: The study design was of a case report and literature review. Setting: Academic tertiary referral practice. Methods: A case was reported, and the literature was reviewed. Results: A 31-year-old woman presented with an enlarged, diffusely firm, nontender, nonmobile, and not particularly nodular thyroid gland with mild compressive symptoms. She had intermittent skin papules and 1 episode of gingival ulceration. Ultrasound showed diffusely, hypoechoic thyroid with dimensions of 36 × 20 × 16 mm on the right and 36 × 16 × 17 mm on the left. No distinct nodules were noted, and thyroid function test results were normal. Laboratory testing for autoimmune abnormalities of the thyroid was negative for antithyroid peroxidase, antiparietal cell, and anti-smooth muscle cell antibodies. She tested positive for serum antithyroglobulin antibodies. A computed tomographic scan demonstrated abnormal low attenuation of her thyroid gland without any distinct nodules or masses. A fine-needle aspiration and core biopsy confirmed the diagnosis of Langerhans cell histocytosis. Dissection was technically challenging because of the firm and nonmobile lobes. Densely adherent strap musculature was encountered bilaterally, and the rare presence of a nonrecurrent laryngeal nerve was noted on the right. Histologically, thyroid parenchyma was largely obliterated by a diffuse infiltrate of mononuclear spindled to epithelioid histiocytes with few residual thyroid follicles. These histiocytes had moderate to abundant pale to eosinophilic cytoplasm, and some had prominent nuclear grooves and indentation/clefts, consistent with Langerhans histiocytes. Plasma cells and lymphocytes were sparsely dispersed. Immunohistochemistry showed that these histiocytes were positive for S-100, and rare lesional histiocytes were also positive for CD1a. Eosinophils were not readily identified in this lesion. Conclusions: Langerhans cell histiocytosis in the thyroid gland is a rarely reported disease, with controversy over its management. This disease should be considered in the differential diagnosis of a diffusely irregular and firm thyroid gland, and multidisciplinary team cooperation is important for its diagnosis and management.