Vascular Proliferation of the Thyroid: Potential Histopathological Pitfalls as a Consequence of Fine Needle Aspiration

Abstract

Objective: Fine needle aspiration biopsy (FNAB) can cause reactive histopathological changes, commonly including haemorrhage and granulation tissue. The literature describing vascular proliferation after FNAB is sparse. We aimed to describe neovascularisation in thyroid gland specimens as a consequence of FNAB. Study Design: We analysed all thyroid histopathological specimens from the Fimlab Laboratories collected between 2010 and 2013 for neovascularisation and distortions in the accompanying tissue. We evaluated HE-stained slides and CD31-, podoplanin-, and Ki-67-immunostained slides. Results: We observed vascular proliferation in 64 out of 787 specimens (8.1%). In these patients, the mean age was 62 years, 43 were female and 21 were male. Previous FNAB data were available in 49 cases (76.6%). In 51 cases (79.7%), the neovascularisation occupied less than 5% of the thyroid gland area. The vessel dilatation was moderate in 28 cases (43.8%) and low in 20 cases (31.3%). In tumours, neovessels were detected within the tumour and in the surrounding tissue. Conclusions: Post-FNAB tissue samples include dilated newly formed vessels, which pathologists should differentiate from rare thyroid vascular tumours. The proposed mechanism is a traumatically induced haemorrhage followed by haematoma and thrombosis that resolves by recanalisation. A knowledge of tissue alteration is needed to avoid misdiagnoses.