Answer: A
Z51.11 is the appropriate code for “Encounter for antineoplastic chemotherapy,” which is done in the patient under treatment for adenocarcinoma.
Option B is not correct because Z51.12 codes for “Encounter for antineoplastic immunotherapy,” which is not done here.
Option C is not correct because C56.2 is for malignant neoplasm of the left ovary, which is not a procedure and also not the primary diagnosis.
Option D is not correct because C56.9 is for malignant neoplasm of the unspecified ovary, which is not the procedure nor the diagnosis in this patient.