Riu's stain and the cytologic diagnosis of thyroid fine-needle aspiration: a single cancer center experience

Abstract

Riu's stain, a Romanowsky-type stain, has been in use in Taiwan over the past 40 years. In order to determine whether it is useful for the diagnosis of thyroid disease in thyroid fine-needle aspiration, we reviewed 254 of these aspirates obtained between April 1990 and June 1996 from patients seen in Koo Foundation Sun Yat-Sen Cancer Center in Taipei. Surgical follow-up was available for confirmation in 61 aspirations. The cytologic diagnosis was categorized into four groups: benign, 174; suspicious, 30; malignant, 41): and inadequate specimen, 9. There were two false-negative and no false-positive diagnoses. Our results showed a sensitivity of 93.5% and a specificity of 100% for the detection of malignancy. If suspicious cases were considered positive, the specificity decreased to 55%, while the sensitivity increased to 95%. We conclude that Riu's stain is a reliable quick stain in the diagnosis of thyroid malignancy. Compared to Papanicolaou stain, it shortens the time needed for a cytopathologist to reach a diagnosis. Papanicolaou stain can be reserved for confirmation.