Primary mediastinal large B cell lymphoma with coexisting aberrations of C-MYC and BCL-2: a case report and literature review

Molecular Characterization of Primary Mediastinal Large B-Cell Lymphomas

Since the description of primary mediastinal large B-cell lymphoma (PMBL) as a distinct entity from diffuse large B-cell lymphomas (DLBCL), numerous studies have made it possible to improve their definition. Despite this, this differential diagnosis can be challenging in daily practice. However, in some centers, PMBL may be treated according to a particular regimen, distinct from those used in DLBCL, emphasizing the importance of accurate identification at diagnosis. This study aimed to describe the histological and molecular characteristics of PMBL to improve the accuracy of their diagnosis. Forty-nine cases of PMBL were retrospectively retrieved. The mean age at diagnosis was 39 years (21-83), with a sex ratio of 0.88. All cases presented a fibrous background with diffuse growth of intermediate to large cells with an eosinophil (26/49, 53%) or retracted cytoplasm (23/49, 47%). "Hodgkin-like" cells were observed in 65% of cases (32/49, 65%). The phenotype was: BCL6+ (47/49, 96%), MUM1+ (40/49, 82%), CD30+ (43/49, 88%), and CD23+ (37/49, 75%). Genomic DNAs were tested by next generation sequencing of 33 cases using a custom design panel. Pathogenic variants were found in all cases. The most frequent mutations were: SOCS1 (30/33, 91%), TNFAIP3 (18/33, 54.5%), ITPKB (17/33, 51.5%), GNA13 (16/33, 48.5%), CD58 (12/33, 36.4%), B2M (12/33; 36.4%), STAT6 (11/33, 33.3%) as well as ARID1A (10/33, 30.3%), XPO1 (9/33, 27.3%), CIITA (8/33, 24%), and NFKBIE (8/33, 24%). The present study describes a PMBL cohort on morphological, immunohistochemical, and molecular levels to provide pathologists with daily routine tools. These data also reinforce interest in an integrated histomolecular diagnosis to allow a precision diagnosis as early as possible.

Prognostic significance of clinical characteristics and 18Fluorodeoxyglucose-positron emission tomography/computed tomography quantitative parameters in patients with primary mediastinal B-cell lymphoma

Objective

Primary mediastinal B-cell lymphoma (PMBCL) lacks standard treatment regimens. This study aimed to identify the disease’s clinical features and prognostic factors.

Methods

This retrospective study included 56 patients with PMBCL. Patient demographic details and clinicopathological characteristics were summarized, and their effects on progression-free survival (PFS) and overall survival (OS) were analyzed.

Results

The median patient age was 29 years (range, 14–56). Twenty-two patients received DA-EPOCH-R (dose-adjusted etoposide, vincristine, and doxorubicin for 96 hours with bolus doses of cyclophosphamide and oral prednisone, as well as rituximab), and 34 patients received R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone). Clinical/laboratory parameters, overall response rates, and 5-year PFS and OS rates did not differ between the treatment groups. Kaplan–Meier analysis indicated that late-stage disease and a higher International Prognostic Index (IPI) were associated with shorter PFS and OS. Furthermore, patients with B symptoms and first-line treatment non-responders exhibited worse OS. ¹⁸Fluorodeoxyglucose-positron emission tomography/computed tomography quantitative parameters, such as higher metabolic tumor volume (MTV) and total lesion glycolysis (TLG), were corrected with shorter PFS.

Conclusions

This study revealed that stage IV disease, higher IPI, and B symptoms were poor prognostic factors in patients with PMBCL. Significantly, higher MTV and TLG portended worse PFS.