Multiple primary malignant tumors (MPMTs) are defined by the presence of two or more histologically distinct malignant tumors, not related to recurrence, metastasis, or local spread in the same individual. These tumors are divided into metachronous and synchronous cancer. Synchronous MPMTs are the second primary cancer occurring within 6 months of the first primary cancer. Meanwhile, metachronous is the opposite of synchronous cancer. The top ten most common MPMTs in the first primary cancer group, ranging from high to low, include breast, thyroid, nonuterine, lung, colon, kidney, uterine, bladder, rectal, and gastric. Despite the prevalence of this cancer, standard treatments are not well established, making management challenging. Therefore, this case presents a 35-year-old female patient with complaints of severe shortness of breath and a history of thyroid cancer. The patient was diagnosed with MPMTs based on histologic examination and treated with chemotherapy agents for clinical improvement.