One promising tracer is the tumor cell-penetrating peptide-based probe TPP [8], which recognizes an epitope of the stress-inducible molecular chaperone Heat shock protein 70 (Hsp70, HSPA1A) that is exclusively present on the cell surface of a large variety of human and mouse tumors, including head and neck [9–11]. The gene discussed is HSPA1A; the disease is neoplasm.