Lance for top injection of a fluid or particulate material in metallurgical vessels, wherein the lance comprises: (a) an inner tube, which is hollow and made of metal, and extending over a length, L, along a longitudinal direction, X1, from an inlet end to a tube end, defining a fluid flow path from the tube inlet to a gas outlet located at or adjacent to the tube end, (b) a sheath of refractory material surrounding the inner tube from the tube end over a length, L1 ≤ L, of the inner tube, (c) an anchoring point rigidly coupled to said inner tube at an anchor level, and at least partially embedded in the refractory sheath, preventing any movement of the inner tube at the anchor level relative to the refractory sheath in the longitudinal direction, X1, (d) an annular gap separating the inner tube from the refractory sheath over a length, Lg, which is at least 50% of L1; (e) at least one annular guide surrounding the inner tube and located within the length, Lg, of the annular gap, said annular guide comprising: - an annular portion having an inner surface and an outer surface, the inner surface facing and circumscribing the inner tube, and - at least two anchor protrusions rigidly extending transversally from the outer surface of the annular portion and at least partially embedded in the refractory sheath, wherein a guide gap is formed between at least 50% of the inner surface of the annular portion and an outer surface of the inner tube allowing the movement of the inner tube with respect to the annular guide along the longitudinal direction, X1 characterized in that, said at least two anchor protrusions are distributed over the external surface of the annular portion, separated from one another by an angle comprised between 90° and 270° measured from the centroid of the annular portion and between the contact points of the two anchor protrusions with the outer surface of the annular portion of the annular guide with the provision that, when the lance comprises several anchoring points distributed along the length of the inner tube surrounded by the refractory sheath, the coupling locations to the inner tube of the two anchoring points most remote from one another in the longitudinal direction X1, are separated by a distance, L0, wherein L0 ≤ 5.5 10 -6 / α [m], wherein α is the coefficient of thermal expansion of the inner tube, and wherein the distance, L0, is in any case not greater than 50 cm. (a) an inner tube, which is hollow and made of metal, and extending over a length, L, along a longitudinal direction, X1, from an inlet end to a tube end, defining a fluid flow path from the tube inlet to a gas outlet located at or adjacent to the tube end, (b) a sheath of refractory material surrounding the inner tube from the tube end over a length, L1 ≤ L, of the inner tube, (c) an anchoring point rigidly coupled to said inner tube at an anchor level, and at least partially embedded in the refractory sheath, preventing any movement of the inner tube at the anchor level relative to the refractory sheath in the longitudinal direction, X1, (d) an annular gap separating the inner tube from the refractory sheath over a length, Lg, which is at least 50% of L1; (e) at least one annular guide surrounding the inner tube and located within the length, Lg, of the annular gap, said annular guide comprising: - an annular portion having an inner surface and an outer surface, the inner surface facing and circumscribing the inner tube, and - at least two anchor protrusions rigidly extending transversally from the outer surface of the annular portion and at least partially embedded in the refractory sheath, wherein a guide gap is formed between at least 50% of the inner surface of the annular portion and an outer surface of the inner tube allowing the movement of the inner tube with respect to the annular guide along the longitudinal direction, X1 - an annular portion having an inner surface and an outer surface, the inner surface facing and circumscribing the inner tube, and - at least two anchor protrusions rigidly extending transversally from the outer surface of the annular portion and at least partially embedded in the refractory sheath,