The role of immunocytochemistry (ICC) in cytological diagnosis of primary and metastatic thyroid tumors

Use of ICC in cytological diagnosis is still limited. For thyroid tumors diagnosis ICC is almost exclusively used to identify medullary cancer and neck lymphnodes metastasis from differentiated cancer in case of scanty cellular fine needle aspiration (FNA) specimen or poorly differentiated tumors. ICC has been performed on 105 FNA specimens destained previously stained with Papanicolaouʹs technique: 38 thyroid nodules, 61 lymphnodes, 3 suspected liver metastasis from medullary cancer. The used markers (Dako) were: thyroglobulin in 20 thyroid nodules and 50 lymphnodes; chromogranin in 35 thyroid nodules, in 26 lymphnodes and 3 liver nodules; calcitonin in 13 thyroid nodules, in 4 lymphnodes and 3 liver nodules; cytokeratins in 22 lymphnodes; vimentin in 2 lymphnodes; CD20 and CD45R0 in 20 lymphnodes; parathyroid hormone (BioGenex) in 3 suspected parathyroid nodules. ICC finding has been essential to diagnose 11 thyroid nodules, 10 lymphnodes, 3 liver metastases and 3 parathyroid adenomas. In 22 thyroid nodules and 40 lymphnodes ICC confirmed the suspected cytological diagnosis. In 16 cases ICC was not useful al all: 4 medullary cancer (2 metastatic) which were chromogranin and calcitonin negative, 7 poorly differentiated carcinoma (5 metastatic) thyroglobulin negative, 1 anaplastic carcinoma thyroglobulin and chromogranin negative, 3 metastases from papillary carcinoma thyroglobulin negative and 1 rabdomiosarcoma which did not show any thyroid, epitelial and lymphoid markers. In conclusion: ICC has been helpful in cytological (FNA) diagnosis of 86.8% of primary thyroid tumors and 82% of their limphnodes metastasis, by performing diagnosis or by confirming the suspected cytological diagnosis.