Here's a curious case. 15mm lesion intimately associated with the parathyroid. The cells are negative for S100, DOG1, PTH, Mammoglobin, NOR1/NR4A3 but positive for CK7. This is the third case I've seen in the last five years of consultation pathology in parathryoids. I've read literature on these and seen them called all sorts of things (mostly salivary gland carcinomas such as acinic or secretory, or benign salivary gland adenomas such as striated duct adenomas). But in my experience these are negative for the defining molecular features of those entities and I actually think this is a 'new entity'. I suspect that they are remnants of Kürsteiner canals (third pharyngeal pouch remnants seen in parathryoid glands). They are usually just simple cysts, but I think they can sometimes be mass-like. I think these account for the nests of PTH negative microfollicles you sometimes encounter in the thymus. This case is new, but the two previous cases have not recurred after simple excision. Has anyone seen similar cases? If so re-tweet with pics and maybe we can put together a series. If I am wrong and you think this is something else, please let me know