POORLY DIFFERENTIATED INSULAR THYROID-CARCINOMA - A CASE-REPORT WITH IDENTIFICATION OF INTACT INSULAE WITH FINE-NEEDLE ASPIRATION BIOPSY

BACKGROUND: Subsequent to the publication of a report in 1984 entitled ''Poorly Differentiated (''Insular'') Carcinoma: A Reinterpretation o f Langhans ''wuchernde Struma,'' poorly differentiated insular thyroid carcinoma (PDITC) has become recognized as a distinct thyroid neoplas m. It is classified morphologically and biologically as an intermediat e entity between well-differentiated (papillary and follicular) and un differentiated (anaplastic) thyroid carcinomas. Only a few publication s have addressed the findings with fine needle aspiration biopsy (FNAB ). CASE: A 67-year-old female presented for evaluation of a massively enlarged thyroid gland. Fine needle aspiration biopsy of the thyroid w ith a 22-gauge needle showed many large, multilayered, round to oval n ests of tumor cells, 0.2-0.4 mm in diameter. Rosettelike configuration s of 8-15 cells, 0.025-0.050 mm in diameter, were also observed. Nests of neoplastic cells in the histologic sections were virtually identic al to those in the fine needle aspiration biopsy specimens. When the p atient developed metastatic cervical adenopathy one year later, a micr ofollicular pattern was seen on both the FNAB and histologic sections. CONCLUSION: When nests of tumor cells, 0.2-0.4 mm in diameter, are id entified in a thyroid FNAB specimen, PDITC should be included in the d ifferential diagnosis. A microfollicular pattern in a metastatic lymph node does not exclude the possibility that the primary tumor is a PDI TC.