Clinicopathologic characteristics of HER2-positive pure mucinous carcinoma of the breast

• Published in: Journal of pathology and translational medicine Vol. 54; no. 1; pp. 95 - 102
• Main Authors: Jang, Yunjeong, Jung, Hera, Kim, Han-Na, Seo, Youjeong, Alsharif, Emad, Nam, Seok Jin, Kim, Seok Won, Lee, Jeong Eon, Park, Yeon Hee, Cho, Eun Yoon, Cho, Soo Youn
• Format: Journal Article
• Language: English
• Published: Korea (South) Korean Society of Pathologists, Korean Society for Cytopathology 01-01-2020; The Korean Society of Pathologists and the Korean Society for Cytopathology; Korean Society of Pathologists & the Korean Society for Cytopathology; 대한병리학회
• Subjects: Archives & records; Breast cancer; breast neoplasms; Cancer therapies; Chemotherapy; Cloning; Epidermal growth factor; Lymphatic system; Medical prognosis; Metastasis; Original; Pathology; Patients; pure mucinous adenocarcinoma; receptor, erbb-2; Software; Surgery; Tumors; 병리학; United States > US; Breast neoplasms; Pure mucinous adenocarcinoma; Receptor, ErbB-2
• ISSN: 2383-7837; 2383-7845
• DOI: 10.4132/jptm.2019.10.24

Pure mucinous carcinoma (PMC) is a rare type of breast cancer, estimated to represent 2% of invasive breast cancer. PMC is typically positive for estrogen receptors (ER) and progesterone receptors (PR) and negative for human epidermal growth factor receptor 2 (HER2). The clinicopathologic characteristics of HER2-positive PMC have not been investigated.
Pathology archives were searched for PMC diagnosed from January 1999 to April 2018. Clinicopathologic data and microscopic findings were reviewed and compared between HER2-positive PMC and HER2-negative PMC. We also analyzed the differences in disease-free survival (DFS) and overall survival according to clinicopathologic parameters including HER2 status in overall PMC cases.
There were 21 HER2-positive cases (4.8%) in 438 PMCs. The average tumor size of HER2-positive PMC was 32.21 mm (± 26.55). Lymph node metastasis was present in seven cases. Compared to HER2-negative PMC, HER2-positive PMC presented with a more advanced T category (p < .001), more frequent lymph node metastasis (p = .009), and a higher nuclear and histologic grade (p < .001). Microscopically, signet ring cells were frequently observed in HER2-positive PMC (p < .001), whereas a micropapillary pattern was more frequent in HER2-negative PMC (p = .012). HER2-positive PMC was more frequently negative for ER (33.3% vs. 1.2%) and PR (28.6% vs. 7.2%) than HER2-negative PMC and showed a high Ki-67 labeling index. During follow-up, distant metastasis and recurrence developed in three HER2-positive PMC patients. Multivariate analysis revealed that only HER2-positivity and lymph node status were significantly associated with DFS.
Our results suggest that HER2-positive PMC is a more aggressive subgroup of PMC. HER2 positivity should be considered for adequate management of PMC.