FINE-NEEDLE ASPIRATION CYTOLOGY DIAGNOSIS OF COLLOID NODULE VERSUS FOLLICULAR VARIANT OF PAPILLARY CARCINOMA OF THE THYROID

The cytologic differential diagnosis of colloid nodule (CN) and rite f ollicular variant of papillary carcinoma (FVPC) is difficult with comm on morphologic features. To assess the utility of 18 cytologic morphom etric parameters ii the diagnosis of these thyroid lesions we evaluate d 31 FNA samples that had histologic confirmation of the diagnoses. Th ese 31 cases included 15 cases of chi, 8 cases of FVPC, and 8 cases of the usual variant of papillary carcinoma (UVPC) for reference values. For the morphometric analysis we used an Optimas 4.0 image analysis s ystem. Comparing the CN group with the UVPC group revealed that eight of the parameters had statistically significant differences. The UVPC specimens were more cellular less cohesive, had presence of papillary cellular groups more frequently larger nuclei (UVPC: 109.33 +/- 30.19 mu m(2) CN: 66.81 +/- 15.02 mu m(2)), higher nuclei to cytoplasmic (N/ C) ratio, larger nucleoli, and present nuclear grooves and nuclear pse udoinclusions more frequently. The FVPC group differed from the CN gro up only in three parameters which included larger nuclei (98.49 +/- 18 .24 mu m(2)), higher N/C ratio, and a more frequent presence of nuclea r pseudoinclusions. When rye compared these two variants of papillary carcinoma, we found that the UVPC specimens had less cellular cohesion , less preservation of the architectural polarity and a more frequent presence of papillary cellular groups than the FVPC. The FVPC can be d ifferentiated from CN based on nuclear changes, which included a large r size, higher N/C ratio, and presence of pseudoinclusions. The absenc e of cellular cohesion and polarity combined with the presence of papi llary; groups are useful ill separating the UVPC from the FVPC. A cuto ff of 75 mu m(2) should be used ill separating benign from malignant n uclei. (C) 1998 Wiley-Liss, Inc.