Fine needle cytology pre-surgical differentiation of parathyroid neoplasms: Is it reliable?

Fine needle cytology (FNC) of a parathyroid neoplasia (PN) is reliable, but needs to be confirmed by Parathormone (PTH) and Thyroglobulin (TG) immunoassay on needle washing or by immunocytochemistry (ICC) evaluation. The differentiation between parathyroid adenoma (PA), atypical adenoma (PAA) and carcinoma (PC) is difficult on histology or even impossible on FNC. The aim of this study was to evaluate possible cytological criteria to classify FNC-PN further.

Twenty-three FNC samples of PN and parathyroid cysts were rather then have been reviewed. The series includes 18 PNs, 4 cysts and 1 Thyr3B (histologically diagnosed as PA). Cytological features were: cellularity, patterns (follicular, solid or papillary), clear, oncocytic, isolated cells, nuclear atypia, cytoplasmic inclusions, nucleoli and mitoses. Data were compared with the histological controls.

Seventeen PNs, 2 cysts and 1 Thyr3B FNC samples were histologically diagnosed as PA (16), PAA (2) and PC (2). Two cysts and 1 PN were not confirmed histologically. Cytological features and incidences were: high cellularity (1 PA, 1 PAA, 2 PCs), follicular (8 PAs, 1 PAA), solid (5 PAs, 1 PC), papillary pattern (1PA, 1 PAA, 1 PC), clear cells (4 PAs, 1 PAA, 2 PCs), oncocytic cells (6 PAs, 1 PAA, 2 PCs), isolated cells (5 PAs, 2 PAAs, 2 PCs), nuclear atypia (2 PAs, 1 PAA, 2 PCs), cytoplasmic inclusions (4 PAs, 2 PCs), nucleoli (2 PCs) and mitoses (2 PCs).

Evident nucleoli and mitoses may suggest the differentiation between PA and PC. However, further investigations are required to confirm these preliminary observations.