Introduction

Thyroid tissue in an ectopic location (choristoma) in gall bladder is a rare entity. We report a case of thyroid tissue in an ectopic location in gall bladder in a 29 year old woman.

Material and Methods:

The patient history and clinical details were obtained from the medical records in our tertiary care hospital. The slides were retrieved from the archive of the pathology department. Informed consent was obtained from the patient.

Case Report

A 29 year old woman came with complaints of recurrent abdominal pain for past 1 year. Abdominal ultrasonography showed multiple gall stones. Cholecystectomy was done. Grossly, the gall bladder showed multiple gall stones. Sections from the gall bladder showed ulceration of the mucosa with lamina propria showing chronic inflammatory infiltrate composed of lymphocytes and fibrosis. Rokitansky Aschoff sinus was also seen. A focus in the wall showed benign thyroid follicles lined by low cuboidal epithelium filled with colloid. Focal lymphoid aggregates were also seen. Few clusters of cells showed nuclear clearing and occasional cells showed grooving. So, a diagnosis of chronic calculous cholecystitis with ectopic thyroid tissue was made. Later thyroid function test showed thyroid hormone levels within normal limits.

Figure 1: Thyroid follicular cells in the wall of gall bladder (40 x)

Figure 2: Thyroid follicular cells(100 x)

Figure 3: Thyroid follicular cells with few cells showing grooving with lymphoid aggregates (400x)

Discussion

Ectopic thyroid is when the thyroid is located in any other location other than its normal anatomical location. The most common location of ectopic thyroid tissue is lingual thyroid (90% of cases)(1,2). While the other locations in the neck are supra hyoid, infrahyoid, submandibular and in thyoglossal duct(1,2). Intra abdominal location of ectopic thyroid is a very rare entity (3). But studies show certain rare intra abdominal locations of ectopic thyroid-oesophagus(4), duodenum(5), adrenal gland(6), porta hepatis (7) and gall bladder (8).

Majority of the cases are asymptomatic and incidental. Diagnosis also depends upon the  location of the ectopic thyroid tissue and the endocrine abnormality associated due to abnormal thyroid hormone levels (8). Technetium-99 pertechnetate is the most useful investigation to identify the thyroid tissue in an ectopic location and also the presence of normal thyroid gland.(10) Ultrasonography, CT, MRI are the other investigations which can be done to identify the ectopic thyroid tissue.

For asymptomatic patients, close follow up is done to look for hormonal imbalance and malignant transformation (9). In symptomatic patients, surgical removal is the treatment of choice(9). In inoperable patients, radioactive iodine can be used(9). Metastatic neoplasm from thyroid has to be ruled out when thyroid is found in an abnormal site before giving a diagnosis of ectopic thyroid (8,10).

Conclusion

Ectopic thyroid tissue in gall bladder is a rare entity. It can be an incidental finding or patients may be symptomatic due to hormonal imbalance. Technetium-99 pertechnetate, CT, MRI and thyroid function test are the investigations to be done. Surgical removal is the treatment of choice. Metastatic neoplasm from thyroid has to be ruled out when thyroid is found in an abnormal site before giving a diagnosis of ectopic thyroid.(8,10)

References

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