PARAGANGLIOMA-LIKE ADENOMAS OF THE THYROID (PLAT) - INCIDENTAL LESIONS WITH UNUSUAL FEATURES IN A PATIENT WITH NODULAR GOITER

We discovered two well-demarcated nodules incidentally in a thyroid re moved because of a nodular goiter. Histologically, the nodules showed a pattern of paraganglioma or so-called paraganglioma-like adenoma of the thyroid (FLAT), with lobules of polygonal and oval cells in a vasc ular stroma, but the immunohistochemical markers typical of paragangli oma, including chromogranin, synaptophysin, Leu 7 and S-100, and thyro globulin, characteristic of FLAT, were negative in the tumor cells. C- cell markers calcitonin and somatostatin were also negative. Stain for neuron-specific enolase (NSE), however, showed a distinctive pattern of reactivity within cells at the periphery of the lobules, whereas al l tumor cells stained positively for keratins. Stain for carcinoembryo nic antigen showed a focal interstitial pattern that corresponded to s mall intercellular spaces filled by microvilli identified ultrastructu rally. This pattern of immunohistochemical staining has not been previ ously described in paraganglioma or in FLAT, and may have implications about the origin and nature of these controversial entities.