Background: Amyloidosis is a systemic disease characterized by the extracellular deposition of amyloid fibrils in different organs and tissues. The thyroid gland may be affected by diffuse or nodular amyloid deposits, along with multiple myeloma (MM) (Amyloid Light-Chain Amyloidosis, AL amyloidosis) or chronic inflammatory diseases (Amyloid A Amyloidosis, AA amyloidosis), but thyroid gland involvement rarely appears as the first clinical manifestation in both conditions. The present study reports a case of primary thyroidal nodular amyloid goiter diagnosed by fine-needle cytology (FNC) in an elderly patient.
Case report: A 66-year-old female patient presented with dysphagia and hoarseness; the patient suffered from rheumatoid arthritis but did not have kidney failure or altered thyroid function. Ultrasound examination (US) showed a 30 mm irregular, hypoechoic area in the left thyroid lobe. FNC showed abundant, dense and amorphous material similar to the one stained in purple at Diff-Quik stain and pinkish at the Papanicolaou. Spindle cells with thin, bland and bent nuclei were scattered in this material; few thyroid follicular cells were also present. An alcohol-fixed smear was stained with Congo red: the amyloid material appeared cherry red and it also showed apple-green birefringence when observed with a polarizing microscope. A differential diagnosis between different thyroid pathologies was considered and the cytological diagnosis of nodular amyloid goiter was pointed out. The patient underwent thyroid lobectomy and the subsequent histological examination confirmed the cytological diagnosis.
Conclusions: FNC is a safe and effective procedure for the diagnosis of thyroid amyloidosis. Congo red-stained smears can be used to demonstrate the presence of amyloid material, showing the typical green birefringence under polarized light. An early and accurate cytological diagnosis may suggest an hematological screening and the appropriate treatment for the thyroid nodule.