Affiliation:
1. From the Departments of Pathology (Nambirajan, Bhardwaj, Jain, Singh), All India Institute of Medical Sciences, New Delhi, India
2. and Pulmonary Medicine (Mittal), All India Institute of Medical Sciences, New Delhi, India
3. Department of Surgical Oncology, Dr B. R. Ambedkar Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India (Kumar)
Abstract
Context.—
Somatic mutations in SMARCA4 (SWI/SNF–related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4) gene and/or BRG1 (Brahma-related gene 1) loss identifies a subset of non–small cell lung carcinomas (NSCLCs) lacking alterations in EGFR (epidermal growth factor receptor), ALK (anaplastic lymphoma kinase), and ROS1 (ROS proto-oncogene 1) genes. Preliminary observations suggest responsiveness to immunotherapy and targeted therapies.
Objective.—
To study BRG1 loss in NSCLCs and elucidate the clinicopathologic profile of such SMARCA4-deficient NSCLCs.
Design.—
Non–small cell lung carcinomas diagnosed during 6 years were subject to immunohistochemistry for BRG1 and BRM (Brahma). Tumors with BRG1 loss were stained with antibodies against thyroid transcription factor 1 (TTF-1), p40, cytokeratins, hepatocyte paraffin 1 (Hep Par 1), Sal-like protein 4 (SALL4), CD34, SRY-box 2 (SOX2), chromogranin, synaptophysin, p53, integrase interactor 1, ALK, and ROS1. EGFR mutation testing was performed by polymerase chain reaction–based method.
Results.—
Among 100 NSCLCs tested, 4 cases (4%) showed BRG1 loss. The histology ranged from solid adenocarcinomas (n = 1) to large cell/poorly differentiated carcinomas (n = 3) with clear cell cytology in 2 cases. All showed loss/reduction of BRM with variable cytokeratin and SALL4 expression, and were negative for TTF-1, p40, Hep Par 1, ALK, ROS1, and EGFR mutations. CD34 and SOX2 were negative in all 4 cases. Isolated BRM loss was common (21%), distributed across all NSCLC subtypes including squamous cell carcinomas and a hepatoid adenocarcinoma.
Conclusions.—
BRG1 loss occurs in a subset of TTF-1/p40–negative poorly differentiated NSCLCs. Identification and follow-up will clarify the prognosis, diagnostic criteria, and potential for therapeutic personalization.
Publisher
Archives of Pathology and Laboratory Medicine
Subject
Medical Laboratory Technology,General Medicine,Pathology and Forensic Medicine
Cited by
42 articles.
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