When gently pinched from the side, a prominent dimple forms in the middle of the mass. What is most likely?

Jacob, a 33-year-old construction worker, complains of a “lump on his back” over his scapula. It has been there for about a year and is getting larger. He says his wife has been able to squeeze out a cheesy-textured substance on occasion. He worries this may be cancer. When gently pinched from the side, a prominent dimple forms in the middle of the mass. What is most likely?

A) An enlarged lymph node
B) A sebaceous cyst
C) An actinic keratosis
D) A malignant lesion