Final answer:
The most common and significant symptom of leiomyomas is menorrhagia, or heavy menstrual bleeding, which is different from the primary symptom of endometriosis, pelvic pain.
Step-by-step explanation:
The most common and most important clinical manifestation of leiomyomas, also known as uterine fibroids, is menorrhagia (heavy menstrual bleeding). This symptom can cause significant anemia and pain, and is a common reason for patients to seek medical attention. While the provided information discusses endometriosis, which is a different condition from leiomyomas, the emphasis here is on the importance of recognizing the clinical signs that differentiate various gynecological disorders. The heavy and irregular menstrual bleeding associated with leiomyomas contrasts with the pelvic pain that is the main symptom of endometriosis. Additionally, leiomyomas can lead to symptoms such as pelvic pressure or pain, urinary frequency, and infertility.