Table of Contents
Washington University Experience | NEOPLASM (SELLAR) | TTF-1-positive sellar tumor - Spindle cell oncocytoma (SCO) | 1L Spindle cell Oncocytoma (Case 1) K167 1
Ki-67 highlights a proliferative index estimated at ~4%. ---- Not shown: HMB-45 is negative in the tumor cells. CK7 immunoreactivity shows focal reactivity as well. PAS is negative in the tumor cells. PAX8 is negative. ---- The overall findings are most consistent with a diagnosis of spindle cell oncocytoma, WHO grade I. The presence of epithelioid tumor cells with abundant eosinophilic cytoplasm that are negative for PAS favors a diagnosis of spindle cell oncocytoma over the other two tumors in the TTF1 group. Given the rarity of these entities, there has been no definitive delineation of distinguishing criteria for sub-classification. Although the tumor cells are diffusely reactive to TTF-1 and show focal reactivity to CK7, features seen in thyroid cancers, the overall histomorphology of the current specimen would be very unusual for any metastatic thyroid cancer. Furthermore, the lack of reactivity to PAX-8 makes the possibility of a metastatic carcinoma from the thyroid even less likely.
