Original Article


Clinical and molecular characteristics of unicentric mediastinal Castleman disease

Antoine Legras, Anne Tallet, Audrey Didelot, Aurélie Cazes, Claire Danel, Angela Hin, Raphaël Borie, Bruno Crestani, Yves Castier, Patrick Bagan, Françoise Le Pimpec-Barthes, Marc Riquet, Hélène Blons, Pierre Mordant

Abstract

Background: Unicentric mediastinal Castleman disease (CD) is a rare condition, poorly characterized due to the small number of cases and the absence of genomic study. We analyzed clinical, radiological, histological and genomic patterns associated with mediastinal CD in a substantial case series.
Methods: We retrospectively reviewed cases of unicentric mediastinal CD managed in 2 French thoracic surgery departments between 1988 and 2012. Clinical, radiological, surgical and pathological data were recorded. On available FFPE blocks we performed mutation screening by next-generation-sequencing, using AmpliSeq™ Cancer Hotspot v2 (Life Technologies) and immunohistochemistry (IHC) (AKT-mTOR pathway).
Results: Eleven patients were identified (mean age 41±15 years, sex-ratio 0.8, median follow-up 78 months). Surgical approach was thoracotomy (n=6), sternotomy (n=4), and VATS (n=1). Additional procedures included thymectomy in three cases, mediastinal lymphadenectomy in two cases, and bilobectomy in one case. One patient presented local relapse as a follicular dendritic cell sarcoma, leading to death 48 months after the first resection. Within 9 patients whose FFPE blocks were available, 2 mutations were found: VHL (p.F119L, 35%, n=1) and JAK3 (p.V718L, 53%, n=1). Phospho-AKT and phospho-mTOR stainings were negative in all cases, whereas phospho-S6RP staining was positive in eight cases, mainly in interfollicular cell cytoplasm.
Conclusions: From this series of patients with unicentric mediastinal CD, we observed 2 cases of potential driver mutations and 8 cases of phospho-S6RP activation not related to AKT-mTOR. Larger studies are required to decipher more precisely the molecular abnormalities and potential therapeutic targets underlying this uncommon condition.

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