A one-piece humoral stem (1) comprising: - a diaphyseal portion (2) which has, orthogonally to a diaphyseal axis, an octagonal cross-section with convex rounded corners； - a metaphyseal portion (3) in the shape of a flared corolla which extends the diaphyseal portion to a proximal face, which has, orthogonal to a central axis, an octagonal cross-section with convex rounded corners； in order that the humoral stem has a peripheral surface provided with eight flat side faces (4) and eight rounded fillets (5) which extend continuously from the diaphyseal portion to the metaphyseal portion, and wherein, on the metaphyseal portion, the rounded fillets progressively widen and the side faces progressively narrow when going from the diaphyseal portion towards the proximal face.
