This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Blood born metastasis is unusual of - 
Select and explain. 
A. Osteosarcoma, B. Medullary carcinoma breast, C. Chorio carcinoma, D. Renal cell carcinoma
B: Medullary carcinoma breast
Answer: B: Medullary carcinoma breast 
Explanation: Lymphatic or vascular invasion is never seen in medullary Carcinoma of breast.
Osteosarcoma, Choriocarcinoma and RCC metastatize to distant organs by vascular invasion.