Fig. 4: Low-grade oncocytic tumor (LOT).
From: Do we need an updated classification of oncocytic renal tumors?
A LOT shows “onocytoma-like” appearance at low power; it has typically a sold growth and capsule is absent. B At higher magnification, LOT is composed of eosinophilic cells with round to oval, “low-grade” nuclei, focally showing perinuclear halos. C, D Frequent finding is a sharp transition from solid areas into loose stromal areas that may show hemorrhage and contain scattered, often elongated and irregularly distributed, individual cells (“boats in a bay” arrangement). E CK7 is diffusely positive. F CD117 (KIT) is typically negative or it is very focally and weakly positive in rare cases. Note rare normal mast cells that mark for CD117.
