Thyroid and Parathyroid Neoplasms with Lipomatous Stroma: Report of Three Cases and Review of the Literature
Abstract Introduction/Objective Tumors with mixed adipose tissue and epithelial components are rare in thyroid and parathyroid glands. Most of them are benign and referred to as adenolipoma (or lipoadenoma). A handful of malignant tumors of thyroid follicular cell origin have been reported with abundant adipose tissue known as thyroid carcinoma with lipomatous stroma (TCLS). Adenolipomas of thyroid or TCLS are usually manifested as large thyroid nodules and evaluated by fine needle aspiration biopsy (FNAB) which frequently yield low-cellularity samples due to abundant adipose tissue. On FNAB, the adipose tissue usually interpreted as contamination of subcutaneous or perithyroid origin. Similarly, adenolipomas of the parathyroid are not frequently identified because of presence of adipose tissue which is a feature associated with normal parathyroid glands. Therefore, these tumors are not often correctly diagnosed preoperatively. For that reason, pathologist should report additional cases about this rare entity to increase our understanding and to decrease preoperative diagnostic error. Methods We report three cases of thyroid and parathyroid tumors with abundant adipose tissue with sonographic, cytologic and histologic features along with literature review. Results Among the reported cases in the literature and our cases; 10 out of 17 cases of thyroid carcinoma with lipomatous stroma are papillary thyroid carcinomas (58.8%), 3 out of 17 cases are papillary microcarcinomas (17.6%), 2 out of 17 cases are noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) (11.7%), and 2 out of 17 cases are minimally invasive follicular carcinomas (11.7%). No cases of poorly differentiated or anaplastic thyroid carcinomas have been reported. Conclusion Lipomatous stroma in thyroid carcinoma appears to be associated with differentiated carcinomas since no reported cases of poorly differentiated or anaplastic thyroid carcinomas are present to our knowledge. Although the presence of fatty tissue does not appear to alter the prognosis of these lesions, the question of the histogenesis of the adipose component is intriguing. Awareness of this unusual feature and increased utilization of multimodal approaches in the evaluation of this entity may increase preoperative detection and the understanding of the histogenesis and its possible significance.