No chemotherapies have been FDA-approved for use in cats despite a growing need for such therapies. Paclitaxel (Taxol®) is one of the most effective anticancer agents used in human cancer therapy today, with potent activity against a variety of cancers in people that also occur in cats. Paclitaxel has been found to kill cancer cell lines isolated from cat tumors in the laboratory, but only one small study has been published evaluating paclitaxel treatment of cats with cancer. In that study, 5 of 9 patients responded to paclitaxel therapy, with 4 of these patients experiencing stable disease and one patient experiencing a partial response. The current FDA-approved formulation of paclitaxel for use in people, which uses a cremophor-based agent to solubilize the drug for injection, causes allergic reactions in dogs and cats. This characteristic of the FDA-approved formulation has largely prevented its use in pets. The investigational drug to be used in this study, Paccal® Vet, uses a formulation that has been created to minimize allergic reactions and therefore improve tolerability. Several clinical trials have been performed or are ongoing with this formulation in dogs, but to date, no studies in cats using Paccal Vet have been undertaken. The primary purpose of this study is to test the tolerability of Paccal Vet in cats and to determine an acceptable dose. A secondary, exploratory goal is to see whether Paccal Vet may have anti-tumor activity in various tumors in cats.