Adrenocortical carcinoma has a low incidence. An uncommon subtype is oncocytic carcinoma, a rare cancer with only 36 reported cases. This variant, identified by oncocytic cells, was described in 1986 and is classified based on the Lin-Weiss-Bisceglia system. Criteria such as a high mitotic rate, atypical mitoses, or venous invasion determine malignancy. Typically, these tumors are solitary and non-functioning, but they exhibit aggressive behavior, often leading to invasion and metastasis, resulting in a high mortality rate. Surgical intervention can improve the 5-year survival rate to 50-60%, with alternative treatments like radiofrequency, radiotherapy, or chemotherapy considered.

A 75-year-old male diagnosed with quiescent IgG kappa Multiple Myeloma presents an adrenal mass (42 x 48 x 42 millimeters) in a follow-up PET-CT. This finding raised suspicion of extramedullary metastatic involvement of his condition. We performed retroperitoneoscopic right adrenalectomy. During the surgical procedure, a vascular injury occurs due to tumor infiltration of the lateral aspect of the inferior vena cava, which was controlled with an endostapler, resulting in minimal blood loss and no hemodynamic repercussions for the patient.

Histopathology indicates a corticoadrenal oncocytic carcinoma with venous invasion, meeting a major criterion, leading to a T2 (>5 cm) R0 classification.

Adrenal oncocytic carcinoma is a rare variant of adrenal carcinoma. This tumor is often incidentally diagnosed because it is non-functional, exhibits indolent behavior, and has a longer recurrence time. Surgical excision with clear margins is the treatment of choice, demonstrating an increase in survival.