To explore the clinical diagnostic features of encapsulated papillary carcinoma (EPC) of breast.

The clinical data of 5 cases of EPC in Yantai Affiliated Hospital of Binzhou Medical University from January 2014 to November 2018 were analyzed retrospectively.

EPC patients were all female, aged from 54 to 70 years old. The first diagnosis was due to breast mass, including 1 case of nipple overflow and 1 case of breast pain. The maximum diameter of the mass was from 1.0 to 4.0 cm, with tough and hard texture, smooth surface, fair movement, no redness or swelling of skin, no dimple or orange skin signs, and no lymph node metastasis in axilla. Breast ultrasound showed that the mass was a solid mass with clear boundary and irregular shape, while MRI showed that the mass was a solid mass with clear boundary and wide base surrounded by cystic fluid and irregular shape. In 5 cases of EPC pathology, there were crispy, round like cystic solid nodules by perusal. Microscopic appearance: there was a layer of thick fibrous capsule surrounded by papillary hyperplasia, which presented a disordered branching papillary structure. No myoepithelial cells were found in the lumen. Immunohistochemical staining showed that estrogen receptor (ER) and progesterone receptor (PR) were all positive. In 4 cases, human epidermal growth factor receptor 2 (HER-2) was negative. In 1 case, HER-2 was positive. In all 5 cases, Ki-67%<5%, CK5/6 and p63 were negative. Four patients were treated with modified radical mastectomy and one with breast conserving surgery.

EPC is prone to occur in elderly women. The first diagnosis is mostly due to a breast mass. Under the microscope, it presents a messy branch papillary structure surrounded by thick fibrous capsule. Immunohistochemical staining shows that the myoepithelium around the lesion is significantly reduced or even absent. These are the important clinical diagnostic features of the disease.