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ICC 2023

Shinya Tajima

Shinya Tajima, Speaker at Oncology Conference
Shizuoka Medical Center, Japan
Title : Relation of luminal and myoepithelial cells in “nuclear-inverse polarity papillary lesions lacking myoepithelail cells” of the breast


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. Relationship between luminal cells and myoepithelial cells of cell-cell interactiton is important for intraductal lesion to invasive lesion in recent time. This microenvironment is correlated many factors especially synaptophysin which marker is advocated Maeda I. and Tajima S. et al. and correlated neuroendocrine marker of CD56. Here, in relation to IDP, we would like to present new concept of two papillary lesions resembling IDP. In the past, lacking myoepithelial cells thought to be invasion and means malignancy. We will present distinctive subtype which pathologists over-diagnose malignant however benign truly. 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. Radiologically, malignancy could not be excluded. Then, breast excision was performed. Histologically, both cases revealed papillary 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 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 disease was observed minimum 62 months of follow-up, despite 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 negative. MUC1 of apical staining means benign. MUC5B is thought the staining positivity means early cancer. Hence our staining status also 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 distinctive and another term of “Tajima tumor” is accepted DOI.

Audience Take Away:

  • If our tumor is commonly diagnosed, it would be better for breast tumor patients.
  • Our knowledge will discover commonsense and contribute to daily pathological diagnoses.
  • In the breast, lactifellous duct is maintained by two cells of cell-cell interaction. One is luminal cell and the other is myoepithelial cell. Usually myoepithelial cells control luminal cells for their invasion. However the two cells of cell-cell interaction disordered, invasive carcinoma arise from the lactifellous duct. Hence, lacking myoepithelial cells are considered invasion and malignancy. However our cases are indicated benign however lacking myoepithelial cells. To learn our new distinctive histological subtype, we can reduce unnecessary operation and increase patients’ Quality of Life.
  • Through our new histological subtype, audience will learn surgical pathology of importance.
  • If our tumor is commonly diagnosed, it would be better for breast tumor patients.
  • Our knowledge will discover commonsense and contribute to daily pathological diagnoses.


Shinya Tajima MD, PhD from Japan, graduate from Keio University School of Medicine. After graduated the university, working in Department of Pathology at the same institution. He learned general pathology. Then he would like to be a specialist of breast pathology. He affiliated at St. Marianna University which is the most breast operation number in Japanese university. He received PhD in Radiologic-Pathology from the same Graduate School of Medicine, Kanagawa, Japan. He worked at the Department of Pathology and Radiology of this latter institution. Now he is working at Department of Diagnostic Pathology of Shizuoka Medical Center.