Abstract:
Breast papillary lesions exhibit broad range. Tajima et al. reported in discrimination between benign intraductal papilloma (IDP) and malignant endocrine ductal carcinoma in situ (E-DCIS), new marker of CD56 is useful for discriminating between benign and malignant. Hence, detecting benign IDP correctly and exclude malignant lesion is important thing in daily pathological diagnoses. Here, in relation to IDP, we would like to present new concept of two papillary lesions at a glance IDP. In the past, lacking myoepithelial cells is thought to be invasion and means malignancy. We will present distinctive histological subtype which pathologists over-diagnose malignant however benign truly. Now we demonstrate two cases of 68- (Case1) and 44-year-old (Case2) female. They have abnormality in the breast. And they came to the hospital for further examination and treatment. Radiologically, malignancy could not be completely excluded. Then, breast excision was performed. Histologically, both cases revealed papillary neoplastic lesions lined by fibrovascular core and nuclear inverse-polarity without atypia. Loss of myoepithelial cells was observed by HE, p63, and calponin. Previous report indicate CK5/6, ER, p63 and MUC3 are important for distinguishing between papillary lesions according to the differential index (based on Allred score) of ([ER total score] + [MUC3 total score])/([CK5/6 total score] + [p63 total score] + 1). Based on this analysis, our 2 cases had benign lesions. Additionally, the Ki-67 index was <1% in both cases, and no evidence of disease was observed minimum 62 months of follow-up for both cases, despite lack of additional treatment. Here, we newly experimented MUC immunostainings in these cases because MUC status is important in breast diseases. We did immunostaining of MUC1,2,4,5AC,5B and 6. The results are MUC2,4,5AC and 6 are negative. MUC1 revealed apical strong staining and also MUC5B was completely negative. MUC1 of apical staining is thought to be benign. MUC5B is thought that the staining positivity means early cancer lesion. Hence our staining status also turn out to be benign without myoepithelial cells. In conclusion, MUC immunostaining status also proved “Nuclear inverse-polarity papillary lesion lacking myoepithelial cells” are benign lesions. Our lesion is histologically distinctive and the term of name is long, also exhibit special biological behavior, someone think “Tajima tumor” might be appropriate.
In this congress, I emphasize lacking of myoepithelial cells does not necessarily indicate malignancy. And I think it will be increase new histological subtype of benign however without myoepithelial cells. This notion is new concept and I would like to discuss with researchers in this congress.
