MON-123 Acute Lymphoblastic Leukemia with Infiltration to Pituitary Gland: A Case Report

Abstract Disclosure: J.A. Puentes-López: None. M.F. Rivera-López: None. M.D. Burguete-Bojalil: None. F.J. Gomez-Perez: None. D. Cuevas-Ramos: None. A previously healthy 31-year-old woman started with headache, decreased visual acuity, galactorrhea, and secondary amenorrhea. Laboratory results showed (normal reference) high calcium of 12.5 mg/dL (<10.3), ionized calcium 6.2 mg/dL (<5.3), and phosphate 4.6 mg/dL (<4.2), creatinine 1.3 mg/dL (<1.2), prolactin 473 ng/mL (<25), and TSH 3.3 (<2.5), with normal free T4 0.93 (<1.3), and low hemoglobin 10 g/dL (>13), and platelets 86,000 (>147000). Additional tests revealed normal 25-hydroxyvitamin D 37 ng/mL (<40), and low 1,25-dihydroxyvitamin D 6.1 pg/mL. (>19), PTH 5.7 pg/mL (>12), PTHrP <1.2 pmol/L (<1.5), and high urinary calcium of 335 mg/24 h (<250). Because of hyperprolactinemia, additional pituitary hormonal evaluation confirmed high prolactin 347 ng/mL, central hypogonadism, and normal ACTH (15 pg/mL, >10), IGF-1 (187 ng/mL, >87), morning cortisol (8.6 µg/dL, >5). She was referred to endocrinologist and hematologist, for a possible prolactinoma, and evaluation of hypercalcemia without hyperparathyroidism, and for study of bicytopenia, and hepatosplenomegaly confirmed with ultrasound, respectively. A peripheral blood smear showed 11% blast cells, and bone marrow aspiration confirmed CD20+ B-cell acute lymphoblastic leukemia (ALL), BCR:ABL-negative, standard risk. Patient was hospitalized for induction chemotherapy with the vincristine, cyclophosphamide, and daunorubicin (CALGB regimen) plus rituximab. Pituitary MRI showed a 11x8 mm intra and paraselar hypointense heterogeneous lesion, in contact with right cavernous sinus. 18-FDG PET-CT showed an abnormal hypermetabolic pituitary gland suggesting malignancy infiltration. After ruling out PTH-independent causes of hypercalcemia, including hypervitaminosis D, PTHrp secretion, hyperthyroidism, and familial hypocalciuric hypercalcemia, the hypercalcemia was attributed of ALL bone activity (usually related with elevated IL-6 and TNF-α), which stimulate osteoclastic bone resorption. Hyperprolactinemia resolved after chemotherapy (4.2 ng/mL) without therapy with dopamine agonists, and menstrual cycles resumed. Therefore, prolactin elevation was considered an acute-phase reactant due to the active hematologic malignancy, which also explained her secondary amenorrhea. New MRI showed reduction of the pituitary lesion suggesting it was infiltrated by ALL. She continued anti-leukemic treatment with consolidation and CNS prophylaxis. Three months later, laboratory results showed normalization of serum calcium (9.0 mg/dL), phosphate (3.6 mg/dL), butt secondary hyperparathyroidism (PTH 106.90 pg/mL) related with 25-hydroxyvitamin D deficiency (14 ng/mL). This case illustrates the coexistence of two endocrinopathies linked to hematologic malignancy, both resolving favorably with chemotherapy. ALL infiltration should be considered in the differential diagnosis of a pituitary lesion. Presentation: Monday, July 14, 2025