AB004. Basaloid carcinoma of the thymus: experience of the RYTHMIC network over an 8-year period
Abstract

AB004. Basaloid carcinoma of the thymus: experience of the RYTHMIC network over an 8-year period

Nicolas Piton1,2, Audrey Mansuet-Lupo3, Lara Chalabreysse4, Romain Dubois5, Véronique Hofman6, Cécile Le Naoures7, Vincent Thomas de Montpréville8, Anne De Muret9, Marie Parrens10, Isabelle Rouquette11, Véronique Secq12, Jean-Philippe Dales13, Damien Sizaret9, Pascale Missy14, Quân Tran14, Édith Bazéli15, Alexander Marx16, Nicolas Girard17, Benjamin Besse18, Thierry Jo Molina15

1Department of Pathology, Rouen University Hospital, Rouen, France; 2Inserm U1245, Normandie Univ, UNIROUEN, Rouen University Hospital, Rouen, France; 3Department of Pathology, Hôpital Cochin, AP-HP and INSERM, Centre de Recherche des Cordeliers, Université Paris Cité, Paris, France; 4Department of Pathology, Groupement Hospitalier Est, Hospices Civils de Lyon, Lyon, France; 5Institut de Pathologie, CHU de Lille, Lille, France; 6Laboratory of Clinical and Experimental Pathology, FHU OncoAge, Biobank 0033-00025, Université Côte d’Azur, Hôpital Pasteur, Nice, France; 7Department of Pathology, CHU of Rennes, Rennes, France; 8Department of Pathology, Marie-Lannelongue Hospital, Le Plessis-Robinson, France; 9Department of Pathology, University Hospital of Tours, Tours, France; 10UMR 1312 INSERM, Department of Pathology, CHU de Bordeaux, University of Bordeaux, Bordeaux, France; 11Centre of Pathology des Coteaux, Toulouse, France; 12Department of Pathology, CHU Felix Guyon Saint-Denis, La Réunion, France; 13APHM, Department of Pathology, Hôpital Nord, Pavillon Etoile, Pôle de Biologie-Pathologie, Marseille, France; 14French Cooperative Thoracic Intergroup (IFCT), Paris, France; 15Department of Pathology, Necker and Robert Debré, AP-HP, INSERM U1163, Imagine Institute, Université Paris Cité, Paris, France; 16Institute of Pathology, Medical University of Mannheim, University of Heidelberg, Mannheim, Germany; 17Institute of Thorax, Curie Montsouris, Institut Curie, Paris, France; 18Department of Medical Oncology, Institut Gustave-Roussy, Villejuif, France

Correspondence to: Nicolas Piton, MD, PhD. Department of Pathology, Rouen University Hospital, Rouen, France; Inserm U1245, Normandie Univ, UNIROUEN, Rouen University Hospital, Rouen, France. Email: nicolas.piton@chu-rouen.fr.

Background: Basaloid carcinoma of the thymus is a well-defined but rare entity. The French RYTHMIC network is dedicated to the management of patients with thymic epithelial tumors, organizing an expert review for each included case.

Methods: To study basaloid carcinoma of the thymus, we selected all RYTHMIC diagnoses comprising “basaloid carcinoma” in the conclusion for panel reviewing.

Results: Between 2013 and 2022, 17 cases were identified. However, 4 large biopsies were discarded (3 poorly differentiated squamous cell carcinomas and 1 composite tumor with a chondroid blastematous component) and 2 small biopsies because of uncertainty of sufficient basaloid feature. In total, the panel retained 11 patients (9 tumor resection, 1 surgical biopsy and 1 needle biopsy), with 64% of males (n=7) and 36% of females (n=4), mean age at diagnosis was 70 [standard deviation (SD) =11, range: 46–82]. Among them, 4/8 were UICC stage I, 1 IIIa, 1 IVa and 2 IVb. Resections were qualified R0 for 6/7 and R1 for 1/7. Two patients metastatic at presentation were alive, with a follow-up of 7 and 8 years. Microscopically, all 11 tumors showed a basophilic appearance; 54% (n=6) contained comedonecrosis, and keratinisation was observed in only 1 case. 8 cases showed peripheral palisading. Cystic changes were observed in 6 cases (54%), with 5 with a “cystic papillary pattern”. In all 11 tumors, the nucleo-cytoplasmic ratio was high and the nucleolus was distinct (7 cases with a small one, 1 medium and 3 large). Seven lesions presented with a high number of mitoses, and the mean Ki67 index on the hotspot was 35% (SD =16). Immunohistochemically, 9/9 tumors expressed p40 (or p63), 10/10 CK5/6, 10/11 CD5, 7/8 CD117, 0/11 NUT, 1/11 chromogranin A (very weak and focal), 2/11 synaptophysin (<50% of tumor cells), 4/11 CD56. During the studied period, we reviewed 1,645 thymic epithelial tumors, the incidence of basaloid carcinoma being 0.7%.

Conclusions: Basaloid carcinoma of the thymus is a challenging diagnosis to make, especially on needle biopsy. Comedonecrosis, cystic papillary pattern as well as coexpression of CD5 and CD117 are important features. Despite a high proliferative index, long survival is observed even when metastatic at presentation.

Keywords: Basaloid carcinoma; thymic epithelial tumor; thymic carcinoma; diagnosis

Acknowledgments

Funding: None.

Footnote

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://med.amegroups.com/article/view/10.21037/med-23-ab004/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the national ethics board of RYTHMIC (n° DC-2021-4624) and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

doi: 10.21037/med-23-ab004
Cite this abstract as: Piton N, Mansuet-Lupo A, Chalabreysse L, Dubois R, Hofman V, Le Naoures C, de Montpréville VT, De Muret A, Parrens M, Rouquette I, Secq V, Dales JP, Sizaret D, Missy P, Tran Q, Bazéli É, Marx A, Girard N, Besse B, Molina TJ. AB004. Basaloid carcinoma of the thymus: experience of the RYTHMIC network over an 8-year period. Mediastinum 2023;7:AB004.

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