This is a biopsy from a 50 year old woman who presented with tremor, sweating, heat intolerance, palpitations, anxiety, diarrhea, and inability to sleep. On exam, you note tachycardia, a wide pulse pressure, hypertension, a prominent stare and lid lag (but no proptosis). Surprised, you find a pelvic mass and ascites. There is no goiter and an iodine uptake test shows minimal uptake in the thyroid.
Challenge: What's going on?
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