Fine needle aspiration cytology of parathyroid lesions

Abstract

Background: There has been an increase in the use of fine needle aspiration cytology (FNAC) for the diagnosis of parathyroid lesions (PLs). Differentiation between a thyroid lesion and a PL is not easy because of their similar features. We reviewed parathyroid aspirates in our institution and aimed to uncover trends in diagnostic criteria.

Methods: We selected 25 parathyroid aspirates (from 6 men and 19 women) confirmed surgically or immunohistochemically from 2006 to 2011.

Results: Major architectural findings of PLs include scattered naked nuclei, loose clusters, a papillary pattern with a fibrovascular core, tight clusters, and a follicular pattern. These architectures were commonly admixed with one another. Cytological features included anisokaryosis, stippled chromatin, a well-defined cell border, and oxyphilic cytoplasm. Eighteen of the 25 patients were diagnosed with PL using FNAC. Seven patients had been misdiagnosed with atypical cells (n=2), benign follicular cells (n=2), adenomatous goiter (n=2) and metastatic carcinoma (n=1) in FNAC. Using clinicoradiologic data, the sensitivity of the cytological diagnosis was 86.7%. The cytological sensitivity decreased to 50% without this information.

Conclusions: FNAC of PL is easily confused with thyroid lesions. A combination of cytological parameters and clinical data will be required to improve the diagnostic sensitivity of PLs.

Keywords: Biopsy, fine-needle; Cytology; Parathyroid lesions.

Fig. 1

Parathyroid adenoma. Cells are positive for chromogranin A (A) and negative for thyroid transcription factor-1 (B).

Fig. 2

Representative cytological features of a parathyroid lesion. (A) A loose cluster demonstrates a round configuration. (B) A tight cluster shows overlapping nuclei. (C) A papillary pattern has a fibrovascular core with parathyroid cells arranged in a vascular network. (D) Smears from an aspirated intrathyroidal parathyroid lesion show a lymphoid pattern (A-D, Papanicolaou stain).

Fig. 3

Representative nuclear features of a parathyroid lesion. (A) Nuclei are uniform and round to oval with stippled chromatin. A few cells show a well-defined cell border and an intercellular window. (B) Eccentric nuclei and anisokaryosis with a few atypical nuclei in the periphery (arrow). (C) An intranuclear pseudoinclusion has a distinct boundary resembling a shape drawn with a pencil (arrow) (A-C, Papanicolaou stain).