Hashimotos thyroiditis (HT) is the most common inflammatory condition of the thyroid gland. In addition to the classic variant of HT, several other subtypes have been identified, such as the fibrous variant (HTFV).
Case history: A 38 years old man noticed a rapidly enlarging lump in his neck month ago. This resulted in discomfort with choking sensation and mild dysphagia. He mentioned weight loss, tiredness and night sweats. He was a smoker and drank alcohol in moderation. He had no other past medical history. On examination he had palpable hard thyroid mass. The USS of the neck showed diffusely enlarged thyroid gland, with uniform alteration in echotexture. There was strikingly mixed reflectivity. The thyroid capsule was intact, with no infiltration into the overlying muscles. The most likely diagnosis was thought to be amyloid goitre. Patient had a core biopsy of the thyroid. CT scan of the neck and thorax confirmed diffusely enlarged thyroid with heterogenous enhancement with no retrosternal extension. There was no significant tracheal deviation or narrowing. His Thyroid function tests showed primary hypothyroidism with FT4 of 6.2 pmol/l (10.825.5), FT3 1.7 pmol/l (3.16.8) and TSH of >100 mU/l (0.274.20). His C reactive protein was 71 mg/l (05). He had high titres of Thyroid peroxidase antibodies 1779 IU/ml (0109) and TSH receptor antibodies were negative. The core biopsy showed marked fibrosis with lymphocyte, eosinophil infiltartes. Immunochemistry showed B and T lymphoid infiltrates with a large population of plasma cells. Features were suggestive of Reidels thyroiditis but there was no significant expression of IgG4 within the plasma cells. This is usually high in Reidels thyroiditis. A diagnosis of Fibrous variant of Hashimotos thyroiditis was made and that would fit with high TPO antibodies. The fibrosclerotic process is the key feature of several thyroid diseases like Reidels thyroiditis (RD). Differential diagnosis between HTFV and RT is based on histological criteria established by Beahrs et al. In HTFV the fibroinflammatory process involves a part or whole gland and it does not include the adjacent tissues. In conclusion, this case shows that the differential diagnosis between HTFV and RD is difficult due to the partial clinical and morphological overlapping and the poor efficacy of conventional cytology as well as presurgical biopsy.
Reference: 1. G. Iannaci, R. Luise, P. Sapere, V. et al. Fibrous Variant of Hashimotos Thyroiditis as a Diagnostic Pitfall in Thyroid Pathology. Case reports in Endocrinology 2013.
18 - 21 May 2019
European Society of Endocrinology