Primary hypothyroidism presenting as pituitary hyperplasia with hyperprolactinemia

Objective To discuss the histological characteristics, immunohistochemical phenotypes, diagnosis and differential diagnosis, treatment and prognosis of one case of primary hypothyroidism presenting as pituitary hyperplasia concurrent with hyperprolactinemia.  Methods and Results A 29-year-old female presented menoxenia for one year, galactorrhea for 3 months, and headache for one week. Head MRI demonstrated a sellar space-occcupying lesion and a pituitary adenoma was suspected. Therefore, the patient underwent an exploratory surgery via transnasal-sphenoidal approach under general anesthesia. During the surgery the lesion was located in the right side of sella turcica. It was hard, tough and gray with poor blood supply. Under optical microscopy, the acinar cells showed a diffuse hyperplasia, with focal nodular expansion. The boundary between hyperplastic and normal acinus was ill-defined. By using immunohistochemical staining, the hyperplastic cells were diffusely positive for synaptophysin (Syn) and thyroid stimulating hormone (TSH), partially positive for prolactin (PRL), and negative for thyoid transcription factor-1 (TTF-1). Lymphocytes were scatteredly positive for leukocyte common antigen (LCA). Ki-67 labeling index was less than 1%. Pathological diagnosis was pituitary hyperplasia. The final clinical diagnosis was hypothyroidism. The patient took levothyroxine sodium (Euthyrox) 100 μg/d continously, and was well during the 13-month follow-up.  Conclusions Preopertive diagnosis of pituitary hyperplasia is difficult．Definite diagnosis could be made by clinical history, typical histopathological characteristics and immunohistochemical phenotypes. Differential diagnosis from pituitary adenoma, especially microadenoma, should be paid attention. DOI: 10.3969/j.issn.1672-6731.2016.04.009