Étude clinique, histologique, phénotypique et moléculaire d’une série de 64 cas de lymphomes B primitifs cutanés à grandes cellules

Abstract : Primary cutaneous large B-cell lymphomas (PCLBCL) can be classified according the new 2017 WHO classification as PCLBCL, leg type or primary cutaneous follicle center lymphoma with large cell morphology (PCFCL-LC). This differential diagnosis has a major prognostic and therapeutic impact but could be difficult for pathologists. We applied the 2017 WHO classification diagnostic criteria to categorize a series of 64 PCLBCL. We tested algorithms developed in nodal B-cell lymphoma identifying cell of origin. We searched MYD88 mutation and we assessed the double-hit and dual expressor status. Morphology and phenotype identified 32 PCLBCL, leg type and 25 PCFCL-LC; 7 lesions remained unclassified. Morphology was less reproducible than immunophenotype. Using Hans-modified algorithm, the 23/25 PCFCL-LC had germinal center (GC) status and the 32/32 PCLBCL, leg type, non-GC status. Survival was poorer for PCLBCL, leg type than PCFCL-LC, intermediate for unclassified cases. Survival was worse for NGC cases. MYD88 mutation was detected in 22 PCLBCL, leg type but was never detected in PCFCL-LC cases. The double-hit status was a very rare event. The dual expression was frequent in PCLBCL and associated with PCLBCL, leg type diagnosis. In PCLBCL, survival was worse for dual expressor cases, and among PCLBCL, leg type, dual expressor cases had a more aggressive disease. Our results support the 2017 WHO classification criteria for PCLBCL diagnosis and confirm the difference of prognosis between PCLBCL, leg type and PCFCL-LC, underlining importance of the differential diagnosis. Besides its prognostic value, the Hans-modified algorithm seems a good tool to differentiate PCLBLC, leg type to PCFCL-LC. We showed the diagnostic interest of MYD88 mutation. In PCLBCL, double-hit status seems useless, but dual expression identifies patients with unfavorable forecast.
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Master Thesis
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https://dumas.ccsd.cnrs.fr/dumas-02069718
Contributor : Bu Carreire Université de Bordeaux <>
Submitted on : Friday, March 15, 2019 - 7:00:26 PM
Last modification on : Friday, April 5, 2019 - 1:18:43 AM

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Sarah Menguy. Étude clinique, histologique, phénotypique et moléculaire d’une série de 64 cas de lymphomes B primitifs cutanés à grandes cellules. Médecine humaine et pathologie. 2018. ⟨dumas-02069718⟩

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