Yolk Sac Tumor
One of the most common architectural patterns in yolk sac tumor is the myxomatous pattern. It consists of neoplastic stellate, spindle, or epithelioid cells in abundant myxoid stroma. Many of these cells are pluripotential mesenchymal cells and can form muscle, cartilage, and bone. Such areas should not be confused with teratoma. These foci are chemoresistant and in rare cases can give rise to sarcoma after treatment. This image shows rhabdomyoblasts admixed with microcystic areas in a yolk sac tumor.