Psammoma body and its precursors in papillary thyroid carcinoma: a study by fine-needle aspiration cytology.

Psammoma bodies (PBs) form an important diagnostic criterion of papillary thyroid carcinoma (PTC), but their mechanism of formation is not clear. Following our observation in a case of PTC that laminated hyaline globules may be the precursor form of PBs, the present study was undertaken to find out their relation to PBs in PTC cases. Fifty-four cases of PTC and 14 follicular neoplasms, diagnosed by fine-needle aspiration (FNA) cytology, were studied by one of the investigators (DKD) to find out the PBs, irregular calcifications, hyaline globules, and other forms made of similar material. PBs along with irregular calcification were present in five PTC cases, PB alone was present in 1 case, and irregular calcification alone was present in 4 cases. Large hyaline globules (LHGs), small hyaline globules (SHGs), branching hyaline cylinders (BHCs), and irregular hyaline deposits (IHDs) were identified in 10, 14, 6, and 9 cases, respectively. One or more of these four forms were present altogether in 18 (33.3%) of PTC cases and none of the follicular neoplasms (P=0.0142). These forms were present in 80.0% of cases with PB/irregular calcifications as opposed to 22.7% in cases without them (P=0.0012). Our observations suggest that LHGs, SHGs, and BHCs are precursors of PBs and IHDs serve as a nidus for irregular calcification. copyright (c) 2004 Wiley-Liss, Inc.