Lymphocytic adenohypophysitis simulating a pituitary adenoma in a pregnant woman

The lymphocytic hypophysitis, appearing in women during the third trimester of pregnancy or early post-partum period, is a rare cause of hypopituitarism and pituitary enlargement. A 39 year-old woman presented in the 37th week of pregnancy with bilateral heteronymous quadrantanopsia, CT indicative of tumorous mass and symptoms of hypopituitarism with decreased thyroid hormone and thyrotrophin levels, and low normal level of cortisol. After the birth of a healthy male child the patient breastfed for 10 days, sight disturbances disappeared, but amenorrhea persisted. Upon admittance the visual field showed no abnormalities. MR of the sellar region confirmed previous CT findings. Endocrinological testing confirmed secondary hypothyroidism and cortisol deficiency, normal levels of prolactin with satisfactory reaction to thyroliberin. Histology showed mononuclear infiltration, and immunohistochemistry revealed T-cells (CD3) at the borders, and B-cells (CD20) in the follicular center. Due to enlargement of the pituitary associated with hypopituitarism, an incorrect diagnosis of a tumor could be made.