[Immunohistochemical characteristics of mammary carcinomas with estrogen-negative and progesterone-positive receptors].

In a series of 256 mammary carcinomas, 22 (8.5%) were positive for progesterone receptors (PR) and negative for estrogen receptors (ER). These cases seem to belong to a distinctive group with a biologic behavior not well understood. In order to contribute to a better understanding of such tumors, their association with different pathologic and immunohistochemical factors were compared with those of the rest of the tumors of the series. The results were that favorable factors such as smaller size, negative axillary lymph nodes and low histologic and nuclear grades were decreasingly associated with tumors that were ER+ PR+; ER+ PR-; ER- PR+; and ER- PR-. In relation to immunohistochemical features, tumors that were ER+ PR+; ER+ PR- and ER- PR+ behaved in a similar way, whereas ER- PR- tumors were different from the rest because fewer expressed bcl-2 (p = 0.0000) and had a greater expression for p53 (p = 0.009) and MIB-1/Ki-67 (p = 0.05). No significant differences were found between the four populations in recurrence rate or metastases, nor overall survival. In conclusion, these findings show that tumors that are ER- PR+ might have biological characteristics somewhere in between ER+ PR+ and ER- PR+.