Large structures within the class of summing operators

We investigate lineability/spaceability problems within the setting of multilinear summing operators on quasi-Banach sequence spaces. Furthermore, we deal with the contemporary geometric notions of pointwise-lineability and $(\alpha ,\beta )$-lineability. Among other results, we prove that the class of multilinear operators taking values on ${\mathrm{\ell }}_q(0<q\le \mathrm{\infty })$ that are absolutely but not multiple summing is pointwise $\mathfrak{c}$-spaceable when non-empty. Spaceability in other classes, such as Dunford-Pettis operators and multilinear operators on general summable scalar families, is also studied.