Parasitic thyroid nodules: Cancer or not? — ASN Events

Parasitic thyroid nodules: Cancer or not? (#312)

Lauren Baker 1 , Anthony Gill 2 3 , Charles Chan 3 4 , Betty Lin 3 4 , Kerwin Shannon 3 5 , Michael Elliott 3 5 , Bronwyn Crawford 1 3
  1. Endocrine, Concord Hospital, Sydney
  2. Pathology, Royal North Shore Hospital, Sydney
  3. Sydney Medical School, University of Sydney, Sydney
  4. Pathology, Concord Hospital, Sydney
  5. Head and Neck Surgery, Royal Prince Alfred Hospital, Sydney

A 58 year-old woman presented with a 3-month history of palpitations, sweating and abnormal thyroid function tests (TSH <0.01mIU/L, normal fT4 17.4pmol/L, elevated fT3 8.0pmol/L). She had no overt signs of thyrotoxicosis or palpable goitre.

Past medical history included left hemi-thyroidectomy for a toxic nodule (follicular adenoma) 1992.

Thyroid ultrasound showed residual right lobe with small nodules <6mm with specs of calcification and several grossly abnormal lymph nodes in the left lower cervical area.

Thyroid isotope scan showed increased uptake in the enlarged lymph nodes in the left lower neck, with minimal uptake in the right lobe.

Fine needle aspiration biopsy of bilateral lymph nodes provided insufficient material for cytology, thyroglobulin washings were positive from the left side only.

Provisional diagnosis: functional metastatic thyroid cancer. Possible primary sites:

i) Left thyroid follicular adenoma.

ii) Micropapillary thyroid carcinoma.

iii) Thyroid cancer in the right thyroid lobe.

Review of the left hemi-thyroidectomy confirmed a 21 mm follicular adenoma. A <1mm papillary microcarcinoma was found. 

Completion thyroidectomy with central and selective bilateral neck dissections was performed. Histopathology demonstrated benign multinodular goitre in the right lobe. All 27 lymph nodes from the right side were normal. The left neck dissection: 24 hyperplastic thyroid nodules and 38 normal lymph nodes. 

The patient received ablative I131 (100mCi) after thyroxine withdrawal (TSH 123mIU/L). Post treatment whole body scan showed uptake only in the thyroid bed with serum thyroglobulin 1.0ug/L.

The probable diagnosis in this case is functional parasitic thyroid nodules1-4 (thyroidosis). This is a rare diagnosis and our case is unusual with 24 nodules. The natural history of this condition is unclear.

Discussion points:

i)               What is the pathophysiology of hyperplastic thyroid nodules?

ii)              Should this condition be treated as malignant?

iii)             Will tumour suppressor genes be informative?

What should be the goals of long-term management?
  1. Harach HR, et al: Thyroid Implants After Surgery and Blunt Trauma. Annals of Diagnostic Pathology 2004;8(2):61-68.
  2. Santos VM, et al: Parasitic Thyroid Nodule in a Patient with Hashimoto’s Chronic Thyroiditis. Rev Hosp Clin Fac Med S Paulo 2000;55(2):65-68.
  3. Shimizu M, et al: Nodule of the Thyroid in a Patient with Graves’ Disease. Virchows Arch 1999;434:241-244.
  4. Assi A, et al: Parasitic Nodule of the Right Carotid Triangle. Arch Otolaryngol Head and Neck Surgery 1996;122:1409-1411.