A 68-year-old woman from Bangalore presents with a 6-month history of a changing dark lesion on her right calf. Examination reveals a 12 mm × 10 mm irregular, darkly pigmented nodule with surface ulceration and surrounding erythema. Histopathology confirms superficial spreading melanoma with a Breslow thickness of 2.5 mm, ulceration present, mitotic rate of 6/mm², and Clark level IV invasion. Sentinel lymph node biopsy shows micrometastases in 2 regional lymph nodes (0.5 mm and 0.8 mm deposits). Staging CT and PET-CT show no distant metastasis. According to AJCC 8th edition, what is the stage of this melanoma?