1. A 39 year old woman presented with a well-defined 1X1.5 cm nodule in the lower pole of the thyroid which was hypoecho in sonography. FNA with Giemsa stain.

12. What is your diagnosis?

13. Differential Diagnoses : 1. Metastatic renal cell carcinoma 2. Medullary carcinoma 3. Parathyroid adenoma 4. Follicular neoplasm

14. Diagnosis : Parathyroid Adenoma

15. Cytologically, parathyroid adenoma can not be distinguished from parathyroid hyperplasia  Cellular smear with small round to cuboidal epithelial cells with high N/C ratio in loosely cohesive groups, isolated cells or in thick syncytial-type tissue fragments ( Mono layered, trabecular, follicular or papillary-like ).  The nuclei is round with coarse granular chromatin, micronocleoli & occasionally with molding of nuclei  Parathyroid cells are smaller than thyroid follicular cells & are composed of chief and oncosytic type cells  Background : proteinaceous fluid or colloid-like material.

16. Parathyroid hyperplasia/adenoma Papillary thyroid carcinoma Thyroid follicular adenoma/carcinoma Cellularity Generally hyper cellular Pattern Cells isolated, loosely cohesive groups or syncitial groups, bare nuclei frequent Cells isolated, loosely cohesive groups or syncitial groups, bare nuclei is not frequent syncitial groups, bare nuclei is not frequent Architecture of tissue fragment Small to large tissue fragment with trabecular, follicular, overlapping of nuclei, perivascular arrangement Monolayered, tridimentional clusters,papillary or follicular pattern Syncitial with or without follicular pattern, overlapping nuclei Cells Small, round cuboidal, poorly defined cell border Variable size, well to poorly defined cell border Variable size, poorly defined cell border Nucleus Round, smooth nuclear membrane, coarsely granular chromatin, micronucleoli, high N/C ratio Enlarged powdery nuclei, groove, inclusion, Micro/Macronucleoli Variable enlarged, fine to coarsely Chromatin with or without Nucleoli

17. Parathyroid hyperplasia/adenoma Papillary thyroid carcinoma Thyroid follicular adenoma/carcinoma Cytoplasm Scant, indiscrenible to modest, clear, granular, oxyphilic VariableScant Psammoma bodies AbsentMay be presentAbsent Background Clean to proteinaceous material, fat globules in hyperplasia No proteinaceous material, fat globules Colloid Absent+/- PTH +-- Thyroglobulin-++ Chromogrnin+--