Hashimoto's thyroiditis

Abstract

As only eight cases have been previously reported in the literature, plasma cell granuloma of the thyroid gland is a rare entity. This condition can be confused with a benign or malignant neoplastic thyroid process. In this article, we describe a new case of plasma cell granuloma of the thyroid gland that occurred in a 46-year-old man who also had Hashimoto's thyroiditis. This case represents only the second documented instance of a plasma cell granuloma of the thyroid occurring in the setting of Hashimoto's thyroiditis. Moreover, it is only the second case of a plasma cell granuloma that has been reported in a male.

Introduction

Plasma cell granuloma is a non-neoplastic proliferation of polyclonal plasma cells within a fibrous stroma. The lesions are typically well circumscribed, but they lack a definitive capsule. Plasma cell granuloma usually occurs in the lungs, but cases of extrapulmonary manifestations have been documented in multiple organs.

In the thyroid gland, plasma cell granuloma is exceedingly rare. Only eight previous cases have been reported worldwide. (1-8) In this article, we describe a new case of plasma cell granuloma of the thyroid. This case is even more rare in that it is only the second documented case that occurred in a patient with Hashimoto's thyroiditis. Moreover, it is only the second case that has been reported in a male; all of the other previously reported cases except one (7) occurred in young or middle-aged women.

Case report

A 46-year-old man who had a history of Hashimoto's thyroiditis and hypothyroidism came to the outpatient clinic at the Denver Health Medical Center with a complaint of a painless left neck mass that had enlarged during the previous 10 months. The patient had been taking thyroid hormone replacement therapy and was otherwise asymptomatic. He also related a family history of thyroid cancer in both his mother and sister, and he was therefore concerned about the possibility of a malignant process in himself as well.

On physical examination, the thyroid gland was firm, enlarged, and bilaterally nodular on palpation, and a dominant nodule was noted in the left thyroid lobe. Laboratory test results included an elevated thyroid-stimulating hormone (TSH) level of 10.46 [micro]U/ml (normal: 0.32 to 5.20), a free thyroxine ([T.sub.4]) concentration of 0.49 ng/dl (normal: 0.50 to 1.70), and a serum total protein measurement of 6.2 g/dl (normal: 6.0 to 8.2).

Analysis of a fine-needle aspiration biopsy specimen could not exclude the possibility of a neoplasm. In view of the patient's history of Hashimoto's thyroiditis and hypothyroidism and his family history of thyroid cancer, a total thyroidectomy was performed. The patient's postoperative course was unremarkable, and he was discharged on hormone replacement therapy.

The resected thyroid specimen was submitted for analysis in two pieces, which weighed 59 grams in aggregate. Both lobes were nodular and firm. The dominant, well-circumscribed, tan nodule in the left lobe measured 5 X 3 X 3 cm. Histologically, both lobes exhibited changes that had been caused by Hashimoto's thyroiditis, including lymphoplasmacytic infiltration with the formation of germinal centers, destruction of the normal thyroid follicular architecture, Hurthle cell changes, and squamous metaplasia (figure). The dominant nodule in the left lobe contained a large, well-circumscribed but unencapsulated aggregation of plasma cells on a background of fibrosis. Also noted in the background were a few remnants of destroyed thyroid follicles. No lymphocytic component was seen in the left nodule.

Immunohistochemical staining for kappa and lambda light chains (Ventana Medical Systems; Tucson, Ariz.) revealed that the plasma cell infiltrates were polyclonal (figure). On the basis of these findings and the histopathologic features, the non-neoplastic nature of the lesion was confirmed and a diagnosis of plasma cell granuloma occurring in the setting of Hashimoto's thyroiditis was established.

Discussion

The benign, polyclonal nature of any plasma cell granuloma must always be confirmed by immunohistochemical staining for kappa and lambda light chains or by some other technique. Histologic examination alone is insufficient to discriminate plasma cell granuloma from plasmacytoma or plasma cell myeloma, even though it rarely manifests in the thyroid.

The etiology of plasma cell granuloma remains unclear. De Mascarel et al hypothesized that plasma cell granuloma represents an exaggerated immunologic response to either an infectious or a noninfectious antigenic stimulus that is initially localized. (5) However, no literature exists to support this theory. Chan et al reported that their case likely originated in a colloid nodule. (3)

In previously reported cases, the status of the thyroid gland function at the time of diagnosis was inconsistently documented. Both normal38 and hypothyroid (1,2,7) states were reported. The most recent case occurred in a 46year-old woman who had euthyroid goiter. (8) In our case, the patient had a long history of hypothyroidism.

Plasma cell granuloma occurring concomitantly with Hashimoto's thyroiditis has been previously described only once before, by Zingrillo et al. (6) They theorized that the presence of Hashimoto's thyroiditis might provide fertile ground for an aberrant but localized polyclonal plasma cell proliferation. Hashimoto's thyroiditis is well known to accompany the development of some neoplastic entities in the thyroid--namely, lymphoma and papillary carcinoma. More case reports are needed before a definitive connection between these entities can be established.

While both plasma cell granuloma and Hashimoto's thyroiditis were present in our patient simultaneously, the link, if any, between the two entities is not clear at this point. No case of malignant transformation or recurrence of plasma cell granuloma has yet been described in the literature.

In conclusion, plasma cell granuloma is a rare but possible cause of a dominant nodule formation in the thyroid gland. Awareness of this entity is important to surgeons, pathologists, and other medical professionals who are faced with the diagnosis and treatment of patients with possible neoplastic lesions of the thyroid gland. Consideration of plasma cell granuloma during the work-up might preclude excessive or improper management.

References

(1.) Holck S. Plasma cell granuloma of the thyroid. Cancer 1981; 48:830-2.

(2.) Yapp R, Linder J, Schenken JR, Karrer FW. Plasma cell granuloma of the thyroid. Hum Pathol 1985;16:848-50.

(3.) Chan KW, Poon GP, Choi CH. Plasma cell granuloma of the thyroid. J Clin Pathol 1986;39:1105-7.

(4.) Talmi YP, Finkelstein Y, Gal R, Zohar Y. Plasma cell granuloma of the thyroid gland. Head Neck 1989;1l:184-7.

(5.) DeMascarel A, Vcrgier B, Merlio JP, et al. Plasma cell granuloma of the adrenal gland and the thyroid: Report of two cases. J Surg Oncol 1989;41:139-42.

(6.) Zingrillo M, Tardia B, Bisceglia M. Plasma cell granuloma of the thyroid associated with Hashimoto's thyroiditis. J Endocrinol Invest 1995;18:460-4.

(7.) Li Voon Chong JS, Burrows CT, Cave-Bigley D, Macfarlane IA. A hard thyroid mass due to plasma cell granuloma. Int J Clin Pract 2001;55:335-6.

(8.) Martinez F, Filipowicz E, Hudnall SD. Plasma cell granuloma of the thyroid. Arch Pathol Lab Med 2002;126:595-8.

From the Department of Pathology, University of Colorado Health Sciences Center, Denver (Dr. Mugler, Dr. Ryder, and Dr. Said), and the Department of Pathology, Denver General Hospital (Dr. Gaido).

Reprint requests: Sherif Said, MD, Director, Head and Neck Pathology, Department of Pathology, B 216, University of Colorado Health Sciences Center, Denver, CO 80262. Phone:(303) 315-5117; fax: (303) 315-6795; e-mail: Sherif.Said@UCHSC.edu

COPYRIGHT 2003 Medquest Communications, LLC
COPYRIGHT 2003 Gale Group