A 58-year-old woman from Mumbai presents with fatigue and bone pain for 4 months. Laboratory findings include hemoglobin 7.8 g/dL, serum calcium 12.2 mg/dL, serum creatinine 1.9 mg/dL, and serum albumin 2.3 g/dL. Serum protein electrophoresis shows an M-spike of 3.8 g/dL. Bone marrow biopsy reveals 28% clonal plasma cells with cytoplasmic immunoglobulin G (IgG) and kappa light chain restriction on flow cytometry. Skeletal survey shows multiple lytic lesions in the skull and pelvis. What is the most likely immunophenotype of the neoplastic plasma cells?