Shrinkage of a pituitary metastasis of melanoma induced by pembrolizumab: a case report

BACKGROUND: Pituitary metastases are rare, often deriving from lung or breast cancer owing to the upper vena cava proximity. Pituitary metastases can manifest with signs and symptoms of pituitary tumors, consequent to mass effect (headache, visual impairment) and/or hormonal alterations (hyperprolactinemia, hypopituitarism, and diabetes insipidus). Immune checkpoint inhibitors burst immunity against tumors, significantly increasing patients’ survival, but their autoimmune side effects frequently involve the skin, the gastrointestinal tract, and the endocrine glands (pituitary, thyroid, pancreas). CASE PRESENTATION: A 77-year-old Caucasian man had undergone trans-nasal sphenoidal surgery for a nonsecreting pituitary macroadenoma in 2001, without remnant or endocrine deficits. In 2016, he was operated for a shoulder melanoma. In February 2018, imaging evaluation demonstrated metastases in lung, liver, and femur. Therefore, treatment with pembrolizumab (anti-programmed death 1) was scheduled in May 2018, but, before starting this therapy, a brain computed tomography performed for a sudden loss of consciousness detected a sellar mass of 17 × 12 mm, which extended to the pituitary stalk and compressed the optic chiasma. Focused magnetic resonance imaging confirmed the size and characteristics of the lesion, while emergency evaluation of the hormonal profile demonstrated an impairment of adrenal and thyroid function. The pituitary lesion demonstrated a remarkable shrinkage (8 × 6 mm), which was confirmed by subsequent imaging evaluations. CONCLUSIONS: This is the first case reporting on effectiveness of immune checkpoint inhibitors in a patient with pituitary metastasis from a melanoma.