Volume 61, December 2022, 152049Abstract

Nodular hyperplasia of the thyroid is a process whereby the gland experiences growth by nodular expansion of thyroid parenchyma. We have encountered 45 patients in whom the process was caused by the growth of well-defined and sharply circumscribed but unencapsulated nodules composed of oncocytic thyroid follicular cells. The lesions arose in 39 women and 6 men, aged 25–69 years (mean = 50.3 years). The surrounding thyroid parenchyma showed features of chronic lymphocytic thyroiditis. The nodules varied from microscopic to 5 cm and appeared to compress the surrounding thyroid parenchyma. Most of the lesions lacked a well-defined capsule. In 26 tumors, the nodules displayed a predominantly follicular pattern of growth; in 8 cases there were admixtures of follicular and trabecular patterns with focal solid areas devoid of follicles. Clinical follow-up in 39 patients ranging from 7 to 22 years (median = 16 years) showed no evidence of recurrence, metastasis, or malignant transformation. One patient died of unknown causes 15 years after the diagnosis, and another patient died 4 years after diagnosis from metastatic colonic adenocarcinoma. Oncocytic nodular hyperplasia is a benign process associated with chronic lymphocytic thyroiditis that should be distinguished from benign and malignant oncocytic (Hurthle cell) tumors of the thyroid.

Introduction

Nodular hyperplasia of the thyroid, also known as sporadic, nonendemic nodular goiter, is one of the most common forms of thyroid pathology encountered in routine practice. It is thought to be caused by a combination of environmental factors (such as lack of iodine) and genetic factors (such as autosomal dominant inheritance) [1]. The follicles in conventional nodular hyperplasia can be of microfollicular, macrofollicular or normofollicular type, but the follicular cells lining the nodules are generally similar to those seen in the surrounding uninvolved normal thyroid. We have studied a series of patients with clinically multinodular goiters in which the thyroid gland was abnormally enlarged due to a proliferation of multiple well-circumscribed and mostly unencapsulated nodules composed of a monomorphous population of oncocytic (Hurthle) cells. All cases occurred in the setting of chronic lymphocytic thyroiditis. Given the multifocality and diffuse nature of the process, the absence of a complete fibrous capsule surrounding most of these nodules, and the background occurrence of chronic lymphocytic thyroiditis, we interpret this as a process of oncocytic nodular hyperplasia of the thyroid against the background of Hashimoto's thyroiditis. Because of the anecdotal propensity for more aggressive behavior in oncocytic tumors of the thyroid, we felt it worthwhile studying these cases to determine their biologic potential. The clinicopathologic features of our cases are described along with a review of the literature.

Section snippetsMaterials and methods

All cases diagnosed as nodular hyperplasia, chronic lymphocytic thyroiditis, Hashimoto's thyroiditis, or autoimmune thyroiditis accessioned in the surgical pathology department at our institution, between the years 2000–2020 were reviewed. Out of a total of 1256 cases, 45 (3.5 %) cases with the features here described were identified. Criteria for inclusion consisted of total thyroidectomies for multinodular goiter or Hashimoto's thyroiditis that showed a multinodular growth with nodules

Clinical findings

There were 39 women and 6 men, aged 25–69 years (mean = 50.3 years). All patients presented with palpable multinodular enlargement of the thyroid gland. 12 patients were mildly hypothyroid at presentation, the remainder were euthyroid. All patients were symptomatic and presented with painless nodular enlargement of the gland that caused compression symptoms. Two patients had concurrent history of cancer in other organs, including colon and uterus. 7 patients had concomitant papillary thyroid

Discussion

Nodular hyperplasia of the thyroid is a benign process characterized by growth and distortion of the gland due to multiple nodules that are composed of follicular epithelium [1]. Hyperplastic nodules are characteristically well-circumscribed and unencapsulated and contain follicular cells that are generally similar to those seen in the surrounding uninvolved thyroid parenchyma. Less commonly, such nodules can be composed of follicular cells that are different and distinct from the surrounding

Funding

No outside sources of funding for this research.

Declaration of competing interest

The authors have no conflicts of interest to disclose.

References (24)R.L. Apel et al.Clonality of thyroid nodules in sporadic goiter

Diagn Mol Pathol

(1995)

H. Studer et al.Natural heterogeneity of thyroid cells: the basis of understanding thyroid function and nodular goiter growth

Endocr Rev

(1989)

View full text

© 2022 Elsevier Inc. All rights reserved.