Nicola Fusco1,2, Elena Guerini-Rocco3, Claudia Augello1,4, Andrea Terrasi1,4, Giulia Ercoli1, Caterina Fumagalli3, Davide Vacirca3, Paola Braidotti5, Antonina Parafioriti6, Marta Jaconi7, Letterio Runza1, Vijayalakshmi Ananthanarayanan8, Fabio Pagni9, Silvano Bosari1,4, Massimo Barberis3, Stefano Ferrero1,2. 1. Division of Pathology, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy. 2. Department of Biomedical, Surgical and Dental Sciences, University of Milan, Milan, Italy. 3. Division of Pathology, European Institute of Oncology, Milan, Italy. 4. Department of Pathophysiology and Organ Transplantation, University of Milan, Milan, Italy. 5. Division of Pathology, San Paolo Hospital, Milan, Italy. 6. Department of Pathology, Orthopaedic Institute Gaetano Pini, Milan, Italy. 7. School of Pathology, University of Milan, Milan, Italy. 8. Department of Pathology, Loyola University Medical Center, Maywood, Chicago, IL, USA. 9. Department of Medicine and Surgery, University of Milan-Bicocca, Monza, Italy.
Abstract
AIMS: Pulmonary adenofibromas are rare benign fibroepithelial tumours of the lung with unknown histogenesis and an indolent clinical behaviour. Their stroma resembles that of solitary fibrous tumours, whereas the glands are composed of respiratory epithelium organized in a phyllodes-like architecture. Differentiation of pulmonary adenofibromas from other more aggressive intrathoracic tumours is clinically relevant. However, their biology is unknown. Here, we sought to characterize pulmonary adenofibromas at a clinicopathological level and to define whether they could be underpinned by a highly recurrent somatic genetic alteration akin to tumours with similar morphology. METHODS AND RESULTS: Seven pulmonary adenofibromas were subjected to immunohistochemical analysis for thyroid transcription factor 1 (TTF1), napsin A, cytokeratin 7, E-cadherin, CD99, CD34, CD31, STAT6, oestrogen receptor (ER), progesterone receptor, androgen receptor, bcl-2, and vimentin, as well as electron microscopy and capillary sequencing on microdissected samples to evaluate the presence of NAB2-STAT6 fusion genes and MED12 exon 2 mutations in their discrete components. A control group comprising pulmonary solitary fibrous tumours, pulmonary hamartomas and breast fibroadenomas was also analysed. We confirmed that the stromal elements of pulmonary adenofibromas pertain to the fibroblastic lineage, and show ER overexpression in 71% of cases, whereas the epithelium consists of TTF1-positive, E-cadherin positive bronchiolar elements. A highly recurrent NAB2-STAT6 fusion variant (exon 4-exon 2) was detected in the stroma but not in the epithelium. No MED12 mutations were identified. CONCLUSIONS: Here, we demonstrate that pulmonary adenofibromas are neoplastic lesions harbouring the molecular hallmark of solitary fibrous tumours.
AIMS: Pulmonary adenofibromas are rare benign fibroepithelial tumours of the lung with unknown histogenesis and an indolent clinical behaviour. Their stroma resembles that of solitary fibrous tumours, whereas the glands are composed of respiratory epithelium organized in a phyllodes-like architecture. Differentiation of pulmonary adenofibromas from other more aggressive intrathoracic tumours is clinically relevant. However, their biology is unknown. Here, we sought to characterize pulmonary adenofibromas at a clinicopathological level and to define whether they could be underpinned by a highly recurrent somatic genetic alteration akin to tumours with similar morphology. METHODS AND RESULTS: Seven pulmonary adenofibromas were subjected to immunohistochemical analysis for thyroid transcription factor 1 (TTF1), napsin A, cytokeratin 7, E-cadherin, CD99, CD34, CD31, STAT6, oestrogen receptor (ER), progesterone receptor, androgen receptor, bcl-2, and vimentin, as well as electron microscopy and capillary sequencing on microdissected samples to evaluate the presence of NAB2-STAT6 fusion genes and MED12 exon 2 mutations in their discrete components. A control group comprising pulmonary solitary fibrous tumours, pulmonary hamartomas and breast fibroadenomas was also analysed. We confirmed that the stromal elements of pulmonary adenofibromas pertain to the fibroblastic lineage, and show ER overexpression in 71% of cases, whereas the epithelium consists of TTF1-positive, E-cadherin positive bronchiolar elements. A highly recurrent NAB2-STAT6 fusion variant (exon 4-exon 2) was detected in the stroma but not in the epithelium. No MED12 mutations were identified. CONCLUSIONS: Here, we demonstrate that pulmonary adenofibromas are neoplastic lesions harbouring the molecular hallmark of solitary fibrous tumours.