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Ectopic thyroid tissue in the uterus

2005; Informa; Volume: 84; Issue: 2 Linguagem: Inglês

10.1080/j.0001-6349.2005.0255d.x

1600-0412

Fahri Yılmaz, Ali Kemal Uzunlar, Nilgün Söğütçü,

Head and Neck Anomalies

Ectopic thyroid tissue occurs mainly along the course of the thyroglossal duct (1). Ectopic thyroid tissue has been found in various human organs including the tongue and the mediastinum (2). Intrauterine thyroid tissue, however, is an extremely rare occurrence. We present the case of an ectopic thyroid in the uterus without evidence of a primary thyroid gland tumor. To our knowledge, this is the first report of an ectopic thyroid in the uterus. A 45-year-old woman was admitted to the Gynecologic Department of the Dicle University Medical Faculty for a hysterectomy after the incidental discovery of multiple uterine leiomyomas. The patient's thyroid gland was slightly enlarged on palpation due to multinodular goiter. The patient had had fine-needle aspiration biopsy for diagnosis but the result of the aspiration was benign. Gross examination showed a deformed uterus due to numerous intramural and subserous leiomyomas; the endometrial mucosa was moderately atrophic and the cervix was affected by erosion–reepithelialization processes (Naboth cysts). The adnexa appeared normal. A sample was taken from a nodular, colloid–hemorrhagic-looking area of 8 mm in diameter in the basal lumina of the endometrium. Histologic examination of this area revealed a circumscribed lesion with follicles containing some colloid substance (Fig. 1). The follicles were uniform and lined with a monolayered cuboidal epithelium, with neither nuclear atypia nor hyperchromatism; no psammoma bodies or papillary structures were found. This thyroid tissue separated the surrounding tissue without infiltrating it (Fig. 2). Immunohistochemical study by the peroxidase–antiperoxidase (PAP) method was performed on formalin-fixed, paraffin-embedded sections, using rabbit antiserum against human thyroglobulin (Dako, Carpinteria, CA, USA). Epithelial cells and colloid substance in the follicles were positive for thyroglobulin. The diagnosis was made of ectopic thyroid tissue in the uterus. Ectopic thyroid tissue surrounding endomyometrial stroma (hematoxylin and eosin stain; original magnification × 100). Follicles filled with colloid lined by a single layer of cuboidal cells on the right and endomyometrial stroma on the left (hematoxylin and eosin stain; original magnification × 200). Ectopic thyroid tissue can be found anywhere along the thyroglossal duct, from the tongue to the mediastinum. Less frequently, thyroid tissue has been reported in the heart, the trachea, the esophagus (3) and the diaphragm (4), and even in the duodenum (5), the biliary tract, the vaginal wall and the sellar region (6), but ectopic thyroid in the uterus has not been documented previously in the English literature. The incidence of clinically detectable ectopic thyroid is unknown because the majority of cases are asymptomatic. Ectopic thyroid tissue as measured by the presence of microscopically confirmed thyroid tissue in cadaver tongues may occur in up to 10% of the population (7). It is difficult to diagnose the ectopic thyroid tissue preoperatively. The histologic findings in our case revealed a close resemblance to the normal thyroid gland, and the immunohistochemical staining for thyroglobulin confirmed that the follicles filled with periodic acid–Schiff-positive colloid are of thyroid origin. Immunohistochemically, calcitonin-positive cells (C-cells) were not detected in the ectopic thyroid (1). The possibility that the intrauterine thyroid tissue may represent a solitary metastasis from an occult thyroid cancer has to be considered. Occult thyroid carcinomas are frequent but are mostly of the papillary type and usually metastasize to the regional lymph nodes rather than to distant organs (6). Histologic examination in our case could not demonstrate cellular atypia, papillary proliferation and psammoma bodies, which are commonly seen in metastatic occult carcinomas of the thyroid. The possibility of a metastasis from an occult thyroid cancer was unlikely in our patient. However, there was slightly nodular enlargment of the gland. Another possibility is that the inuterin thyroid tissue represents part of a teratoma, but inuterin teratomas are quite rare (8), and despite examination of large numbers of sections, no elements other than thyroid tissue were noted in our case. Metaplasia to follicular cells of the endometrial epithelium has not been defined so far. Ectopic thyroid tissue in the uterus may be explained in two ways: first, and most probably, metastasis of the thyroid follicular epithelial cells via blood; and second, ectopia of the congenital thyroid tissue, which has not been defined up to now. A sample of the patient's thyroid gland was obtained using fine needle aspiration. As a result, in our case, metastasis of the benign thyroid follicular epithelial cells via blood is the most likely explanation.