Aggressive Prolactinoma with Progression to Pituitary Carcinoma: A Case Report

Adenomas of the pituitary gland, predominantly prolactinomas, can exhibit aggressive behavior. Aggressive prolactinomas are characterized by radiographic invasion, rapid growth, clinically significant progression despite standard therapies, and recurrence after surgery or radiotherapy. Pituitary carcinoma is rare (0.1-0.2% of pituitary tumors) [1, 2]. Case Presentation: In 2005, a 50-year-old man presented with bitemporal hemianopsia and severe asthenia due to a large pituitary tumor. Hormonal tests revealed hyperprolactinemia and panhypopituitarism; he received hormonal replacement and dopamine agonists (DA) therapy with a reduction in prolactin levels. Ten years later, he experienced tumor regrowth consistent with pituitary apoplexy and VI cranial nerve palsy. MRI showed a macroadenoma with suprasellar extension and compression of the optic structures. The patient underwent transsphenoidal surgery in view of the partially resistant disease. Histopathology showed a pituitary macroadenoma, and immunohistochemistry showed a high mitotic index (Ki-67 80%). In 2016, the patient developed a partial deficit of the left sixth cranial nerve. He underwent a new surgery but with incomplete resection. In view of the aggressive and resistant nature of the disease, he received radiotherapy. In 2020, prolactin levels began to increase again. MRI showed an occipital- temporal lesion. Subsequently, he underwent radiotherapy and started chemotherapy with temozolomide, resulting in the normalization of prolactin levels in the absence of DA therapy. The patient is currently in remission, with no evidence of tumor recurrence. Conclusion: It was found that 15% of prolactinomas are resistant to DAs, and resistance to DA may signal malignant transformation. Therefore, multimodality therapy and molecular analysis are critical for aggressive prolactinomas and pituitary carcinoma.