Thymic cancer, which refers to the malignant tumor that occurs in the thymus, predominantly presents as squamous cell carcinoma. It generally arises in the mediastinum, with clinical symptoms such as chest pain, cough, and breathing difficulties.

Breast cancer, on the other hand, refers to the malignant tumor occurring in the breast tissue, with invasive ductal carcinoma being the most common type. Its symptoms often include unintentionally discovered breast lumps, or metastasis to axillary lymph nodes, felt as enlargement of these nodes.

Therefore, these two diseases differ in their sites of origin, symptoms, pathological types, and treatments.