[Lymphocytic adenohypophysitis: MRI findings of a suspected case].

We report a case of a 26-year-old woman who had developed decrease of visual acuity, and restriction of the temporal visual field of the left eye in the 30th week of gestation. A skull roentgenogram showed no abnormality, but a pituitary mass was visualized by plain computed tomographic scan. Magnetic resonance imaging (MRI) demonstrated a symmetric sellar mass which had homogeneous signal intensity in all pulse sequences. T1 relaxation time of the mass was elongated as compared with that of a normal pituitary gland. The height of the mass was 11mm, and optic chiasm appeared compressed by the mass. Her visual disturbance improved before delivery, and the size of the pituitary mass regressed spontaneously. Although no histological examination was carried out, the most likely explanation for this phenomenon is lymphocytic adenohypophysitis. Early surgical intervention is not required for lymphocytic adenohypophysitis, because this disorder may be self-limiting, and may resolve itself. Most of these cases have been reported in women, often coincident with pregnancy. So we consider that MRI is the most useful and safest method for diagnosis and follow-up of this disease.