Shirong Ma1, Danhui Zhao1, Yixiong Liu1, Joseph Rohr2, Fan Zhang3, Ying Ma4, Li Gong5, Huijuan Shi6, Yingmei Wang1, Linni Fan1, Junhui Qin1, Zhe Wang1, Shuangping Guo1. 1. Department of Pathology, The Basic Medicine Science and the First Affiliated Hospital of the Air Force Military Medical University, Xi'an, Shaan Xi Province, China. 2. Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, USA. 3. Department of Pathology, The First Affiliated Hospital of Wannan Medical College, Wuhu City, Anhui Province, China. 4. Department of Pathology, Shengjing Hospital of China Medical University, Shen Yang, Liao Ning Province, China. 5. Department of Pathology, The Second Affiliated Hospital of the Air Force Military Medical University, Xi'an, Shaan Xi Province, China. 6. Department of Pathology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guanggong Province, China.
Abstract
AIMS: Pleomorphic adenoma (PA) of the breast, and especially its malignant transformation, is extremely rare and represents a diagnostic pitfall. Molecular alterations in this entity have not been investigated. We aimed to examine the clinicopathological features of our breast PAs and perform molecular analysis. METHODS AND RESULTS: Seven cases of breast PA, including two cases of carcinoma ex PA, were analysed. PLAG1 and HMGA2 gene rearrangements were assayed by fluorescence in-situ hybridisation (FISH) and RNA sequencing (RNA-Seq), respectively. Reverse transcription-polymerase chain reaction (RT-PCR) and Sanger sequencing were used to verify RNA sequencing results. All seven cases of breast PA occurred in women. The histological features were similar to the analogous tumour in salivary glands, including a dual epithelial-myoepithelial component and negativity of oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) by immunohistochemistry. Of the two cases with carcinoma ex PA, one demonstrated minimal invasion and one was extensively invasive. PLAG1 rearrangements were identified in two cases (28.6%), but no rearrangements of HMG2A were found. A novel fusion product in PAs, TRPS1-PLAG1, was identified in one case. No patients had recurrence or metastasis with a follow-up period of 6-158 months. CONCLUSIONS: Breast PA is rare, but it is an important differential diagnosis of breast pathology with the potential to develop carcinoma ex PA. We report a novel TRPS1-PLAG1 fusion gene in breast PA.
AIMS: Pleomorphic adenoma (PA) of the breast, and especially its malignant transformation, is extremely rare and represents a diagnostic pitfall. Molecular alterations in this entity have not been investigated. We aimed to examine the clinicopathological features of our breast PAs and perform molecular analysis. METHODS AND RESULTS: Seven cases of breast PA, including two cases of carcinoma ex PA, were analysed. PLAG1 and HMGA2 gene rearrangements were assayed by fluorescence in-situ hybridisation (FISH) and RNA sequencing (RNA-Seq), respectively. Reverse transcription-polymerase chain reaction (RT-PCR) and Sanger sequencing were used to verify RNA sequencing results. All seven cases of breast PA occurred in women. The histological features were similar to the analogous tumour in salivary glands, including a dual epithelial-myoepithelial component and negativity of oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) by immunohistochemistry. Of the two cases with carcinoma ex PA, one demonstrated minimal invasion and one was extensively invasive. PLAG1 rearrangements were identified in two cases (28.6%), but no rearrangements of HMG2A were found. A novel fusion product in PAs, TRPS1-PLAG1, was identified in one case. No patients had recurrence or metastasis with a follow-up period of 6-158 months. CONCLUSIONS: Breast PA is rare, but it is an important differential diagnosis of breast pathology with the potential to develop carcinoma ex PA. We report a novel TRPS1-PLAG1 fusion gene in breast PA.