Specifically, retained/weak PAX-8 with interspersed TTF-1 in an adnexal carcinoid is a distinct pattern to be aware of when dealing with carcinoid tumors of unknown etiology, strongly favoring an ovarian primary origination (specifically, from struma ovarii) and not metastasis from the gastrointestinal tract or other Mullerian tissues. Here, TTF1 is linked to carcinoid tumor.