Resistant PRL-secreting PitNET associated with breast carcinoma: a case report and literature review

In several studies, hyperprolactinemia has been associated with increased breast cancer risk. Evidence shows that prolactin (PRL) is linked to mammary tumorigenesis, especially in postmenopausal patients, but the data remain controversial. We present a case of a 67 year-old patient with a resistant PRL-secreting PitNET who subsequently developed breast cancer. The patient was known to have persistent high PRL levels despite multimodal treatment (surgery, radiotherapy, and high doses of cabergoline). The tumor specimens obtained after transsphenoidal intervention were histologically and immunohistochemically examined for the following parameters: anterior pituitary hormones, the ki-67 labeling index, CAM 5.2 expression, ER ∝ expression, and somatostatin receptors, which revealed a densely granulated tumor with intense positivity for PRL and ER ∝ , a ki-67 labeling index of 6% and negative MGMT expression. Years later, the patient was diagnosed with breast carcinoma. Histopathological and immunohistochemical examination of the tumor specimen obtained after radical mastectomy confirmed ductal invasive breast cancer with negative immunostaining for prolactin receptors (PLRr) but positive immunostaining for estrogen (ER) and progesterone receptors (PGR) and a ki-67 labeling index of 8%. PRL is involved in mammary development and differentiation, which leads to lactation, the major driver during pregnancy, by regulating ovarian progesterone production. On the basis of the physiological actions of PRL, a role for this hormone in breast cancer has been suggested. Few cases of different types of breast carcinoma associated with hyperprolactinemia due to a pituitary tumor have been reported in the literature. The association between hyperprolactinemia and the risk of breast carcinoma is not well understood. Immunohistochemistry evaluation of PLRr can be helpful to provide information in these cases.