Therapeutic challenges of giant invasive cystic macroprolactinoma.

Summary: Giant cystic prolactinomas are extremely rare, with only four cases previously reported in the literature. Herein, we report the case of a 59-year-old male who presented with an acute decline in visual acuity. An urgent brain MRI revealed a large intra- and suprasellar tumor, consisting of a solid (48 × 31 × 23 mm) and a cystic suprasellar (39.9 × 38.7 × 26.3 mm) component, with cavernous sinus invasion and optic chiasm compression. Hormonal workup revealed hyperprolactinemia (1,020 ng/mL) and panhypopituitarism. The patient was initially treated with bromocriptine. After 3 months, his serum prolactin levels increased despite adequate dosing, and no improvement was observed in his visual deficits. Consequently, he underwent transcranial surgery with subtotal tumor resection. Histopathological examination confirmed PRL-secreting pituitary adenoma. Postoperatively, despite sequential treatment with bromocriptine and cabergoline (maximum approved dose of 3 mg/week), prolactin levels failed to normalize. Furthermore, follow-up MRI revealed a persistent 29 × 21 × 33 mm intra- and suprasellar tumor. This report presents a case of a dopamine agonist (DA)-resistant giant cystic prolactinoma, highlighting the therapeutic challenges associated with this rare tumor subtype. Learning points: Giant cystic prolactinomas are extremely rare. Dopamine agonists remain the first-line therapy for both giant and cystic prolactinomas. Early surgical intervention is indicated for vision-threatening conditions or in cases of dopamine agonist resistance.