Pituitary adenoma with ossification is a rare histological variant. Previously there have been four cases reported in the literature. Here a case of pituitary
prolactin-producing
adenoma with bone formation in a 21-year-old woman is described. The patient had
irregular menstruation for three years. MRI revealed an unusual 1.5 cm(3) ovoid nodule with partial shell-like structure showing heterogeneous signals. The pre-operative
prolactin serum level was 258.78 ng/mL. The patient was operated through the trans-sphenoidal pathway under
general anesthesia. Histologically, the
tumor was parenchymal and mostly replaced by the well-differentiated lamellar bony tissue. Sheets of
tumor cells interweaved with the mature lamellar bone trabeculae showing no cellular atypia. The cytoplasm of the
adenoma cells was slightly eosinophilic and the myelo-adipose metaplastic foci were also found within the parenchyma. Immunohistochemical staining of
tumor cells showed positive expressions of
prolactin,
synaptophysin and
chromogranin A in the cytoplasm of the
tumor cells. Meanwhile, negative expressions of S-100,
epithelial membrane antigen, GFAP and other
pituitary hormones were also demonstrated. As a rare histological variant of
pituitary adenoma, the current case of pituitary
prolactin producing
adenoma with ossification is reported. It is speculated that the ossification may be derived from the osteo-
metaplasia of mesenchymal fibroblasts resulting from the effects of both secondary
ischemia by the outgrowth of the
tumor and/or the autocrine effect of
prolactin in this case. The bony shell structure may limit the growth of
pituitary adenoma.