Expression of novel neuroendocrine markers in breast carcinomas: a study of INSM1, ASCL1, and POU2F3

• Published in: Human pathology Vol. 127; pp. 102 - 111
• Main Authors: Zhong, Elaine, Pareja, Fresia, Hanna, Matthew G., Jungbluth, Achim A., Rekhtman, Natasha, Brogi, Edi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2022; Elsevier Limited
• Subjects: Antigens; ASCL1; Basic Helix-Loop-Helix Transcription Factors; Biomarkers, Tumor - metabolism; Breast cancer; Breast Neoplasms; Cancer; Carcinoma, Neuroendocrine - pathology; Chromogranins; Classification; Female; hASH-1; Humans; INSM1; Metastasis; Morphology; Mucins; Neuroendocrine; Octamer Transcription Factors; POU2F3; Repressor Proteins - metabolism; Retrospective Studies; Stains & staining; Statistical analysis; Synaptophysin - metabolism; Transcription Factors; Tumors; hASH-1; Breast cancer; INSM1; ASCL1; Neuroendocrine; POU2F3
• ISSN: 0046-8177; 1532-8392; 1532-8392
• DOI: 10.1016/j.humpath.2022.06.003

INSM1, ASCL1, and POU2F3 are novel transcription factors involved in neuroendocrine (NE) differentiation of neoplasms in several organs, but data on their expression in breast carcinomas (BCs) are limited. We retrospectively evaluated the expression of these markers in a series of 97 BCs (58 with NE morphology and 39 with otherwise uncommon morphology) tested prospectively using immunohistochemistry (IHC). Nuclear staining in >50% of the cells was used as the positive cut-off. Thirty-two of the 97 BCs (33%) were INSM1-positive. INSM1-positivity correlated significantly with histologic type and presence of stromal mucin. INSM1 also correlated with synaptophysin and chromogranin, established markers of NE differentiation (P < .0001 and P = .0023, respectively). In BC with NE morphology, the expression of INSM1 supported NE differentiation, and INSM1 was more specific than synaptophysin and more sensitive and specific than chromogranin. INSM1 was the most expressed NE marker in 17 BCs. INSM1-positive BCs included 56% of solid papillary BCs, 88% of BCs with solid papillary features, and 75% of high-grade NE carcinomas. Of 35 BCs tested for POU2F3 and ASCL1, only 1 and 4 cases were positive, respectively. Our results show that INSM1 is a sensitive marker of NE differentiation in BC and should be included with synaptophysin and chromogranin in the IHC panel used to evaluate NE differentiation in BC with NE morphology. ASCL1 and POU2F3 are uncommon in BC and their routine assessment is not warranted. •INSM1 is a sensitive and specific neuroendocrine marker in breast carcinoma.•INSM1 expression is prevalent in mammary solid papillary carcinoma.•ASCL1 and POU2F3 are uncommonly expressed in breast carcinoma.