Final answer:
A tender, well-defined and freely moveable lump in a young individual that fluctuates with the menstrual cycle is more likely to be fibrocystic breast changes than cancer. Cancerous lumps are typically hard, immobile and not cycle-related. Accurate diagnosis requires medical evaluation, which might include imaging and biopsy.
Step-by-step explanation:
When a 20-30-year-old presents with a freely moveable, well-defined lump that is tender with their menstrual cycle, it is more likely to be fibrocystic changes rather than cancer. These fibrocystic changes are common and represent benign breast conditions where the breast feels lumpy or rope-like in texture. These changes can vary with the menstrual cycle and often become more noticeable or tender in the time leading up to a period.
Benign tumors or growths such as breast fibroids, are not life-threatening and may be surgically removed if they cause discomfort or have the potential to become cancerous. Cancerous lumps tend to be irregular in shape, immovable, and are not usually associated with the menstrual cycle.
Testicular cancer is another consideration in this age group but with differing symptoms, including a lump or swelling in one testis, and it often does not show cyclical tenderness. Swollen lymph nodes could also be a sign of cancer, like lymphoma, but in young individuals, it is more commonly due to infections.
For a conclusive diagnosis, medical evaluation including a physical exam, imaging, and possibly a biopsy, is necessary. This will help differentiate between benign breast conditions and malignant tumors, ensuring appropriate treatment.