ALT-803 SQ injection-site reaction. (A) Shown is a representative injection site rash manifested as pink, edematous, nontender spreading plaque mimicking cellulitis. The sequence of rash expansion from days 1, 5, and 7 from different patients (left) and an additional example of the rash at day 7 (right). (B) Skin biopsy specimen showed a superficial and deep perivascular and perieccrine infiltrate consisting primarily of lymphocytes (hematoxylin and eosin, original magnification ×50). (C-E) Immunohistochemical analysis revealed that a predominance of cells were positive for CD56 (original magnification ×200) (C), negative for NKp46 (original magnification ×200) (D), and positive for TCRγ3.20 (original magnification ×200) (E), indicating presence of γδ T cells. Results are shown for 1 patient and are representative of 4 injection site reactions analyzed.