Mantle cell lymphoma (MCL)

Epidemiology & Classification

• Incidence: ~5 to 7% of NHL (~6% of all NHL); ~4 to 8 per 1,000,000/yr; M:F ~3:1; median age ~65 to 70.
• Presentation: usually advanced disease. ~90% involve extranodal sites (GI tract, liver, bone marrow), generalized adenopathy is common, and CNS involvement rises markedly with the blastoid variant.
• WHO 2022 / ICC 2022 entities:
  • Classic MCL: SOX11+, IGHV unmutated, nodal/extranodal, often advanced.
  • Leukemic non-nodal MCL (indolent variant): SOX11−, IGHV-mutated, peripheral blood + spleen ± BM, absent or minimal nodal disease; behaves like CLL, presents with splenomegaly and peripheral blood involvement; "watch & wait" eligible.
  • In situ mantle cell neoplasia (ISMCN): cyclin-D1+ cells in mantle zones of otherwise reactive nodes; usually incidental, low progression rate.
  • Aggressive variants: blastoid (high Ki-67, leukemic, CNS-prone) and pleomorphic; both poor prognosis.

Pathology & Diagnosis

• Morphology: nodular to diffuse pattern of small lymphocytes.
• Hallmark: t(11;14)(q13;q32) → IGH-CCND1 fusion → cyclin D1 overexpression. Detectable by FISH or cyclin D1 IHC.
• SOX11+: supports (not confirms) CCND1-negative cases (~5%); not specific (also +in lymphoblastic/some Burkitt); assess CCND2/CCND3; also helps distinguish indolent leukemic non-nodal (SOX11−) from classic MCL.
• Phenotype: cyclin D1+, CD5+ (a T-cell marker aberrantly expressed here), CD19+, CD20+ (bright), FMC7+, IgM/IgD+; CD23− (vs CLL CD23+), CD10−, BCL6−, BCL2+; ± SOX11, ± p53.
• Molecular: t(11;14)(q13;q32) leads to constitutive cyclin D1 expression (the defining lesion).
• TP53 mutation / del 17p: ~10 to 20%; major adverse prognostic factor; chemo-refractory; consider novel agents + allo-HSCT.
• Ki-67 ≥30%: high-proliferation index; adverse. Used in MIPI-c.
• Workup: PET-CT, CT C/A/P, BM biopsy (involved in ~70%), EGD/colonoscopy if clinically indicated or to confirm limited-stage disease (histologic GI involvement common even with normal-appearing mucosa), echo, HBV/HCV/HIV.

Prognosis

• MIPI (age, ECOG, LDH, WBC) → low/intermediate/high risk.
• MIPI-c incorporates Ki-67 (adds proliferation to the clinical score).
• High MIPI portends markedly worse survival (e.g., median OS ~4 yrs in the high-MIPI subset of the Nordic experience).

Frontline Treatment: Younger / Fit (≤65 to 70)

• TRIANGLE (Dreyling Lancet 2024; PMID: 38705160): 3-arm RCT, R-CHOP/R-DHAP+ASCT (control) vs +ibrutinib+ASCT (A+I) vs +ibrutinib without ASCT (I). 3-yr FFS: A+I 88% > A 72% (HR 0.52), I 86% vs A 72%; superiority of ASCT (A) over ibrutinib-without-ASCT (I) not shown. New standard: ibrutinib-containing induction; ASCT may be omitted for many. Toxicity highest in A+I (post-ASCT + ibrutinib maintenance).
• Intensive immunochemotherapy + ASCT (fit patients), options include:
  • Nordic regimen (MCL-2): dose-intensified R-Maxi-CHOP alternating with rituximab + high-dose cytarabine → CR → ASCT → rituximab if molecular relapse. Outcomes: median EFS ~7.4 yrs, median PFS ~8.5 yrs, median OS ~12.7 yrs; late toxicity included secondary malignancies (11/160).
  • Alternating R-CHOP/R-DHAP + ASCT; R-DHA + platinum (RDHAP); R-hyper-CVAD + rituximab (conflicting data on need for HDT/ASCT consolidation); rituximab-bendamustine followed by rituximab + high-dose cytarabine.
• Maintenance rituximab: rituximab × 3 yrs post-ASCT improves PFS and OS (LyMa, Le Gouill NEJM 2017). Note this OS benefit of maintenance R is seen in MCL, unlike in follicular lymphoma.
• TP53-mutated: avoid intensive chemo (chemo-refractory); enroll in trial (BTKi + venetoclax + rituximab; consider allo-HSCT in young fit patients).

Frontline Treatment: Older / Less Fit

• Bendamustine + rituximab (BR) is a core less-intensive backbone. BRIGHT study (Flinn Blood 2014) and StiL NHL1 (Rummel Lancet 2013): in indolent NHL and MCL, BR gave CR ~31% vs 25% and ORR (CR+PR) ~97% vs 91% vs R-CHOP/R-CVP, with better tolerability (BR more nausea/vomiting, pyrexia, chills, hypersensitivity, rash, pruritus; R-CHOP more febrile neutropenia, mucositis, neuropathy, alopecia).
• SHINE (Wang ML NEJM 2022; PMID: 35657079): ibrutinib + BR vs BR alone in patients ≥65: PFS benefit (mPFS 80.6 vs 52.9 mo, HR 0.75) but NO OS benefit and increased toxicity / treatment-related deaths. FDA pulled the ibrutinib MCL indication in 2023; acalabrutinib/zanubrutinib preferred.
• ECHO (acalabrutinib + BR, age ≥65): mPFS 66.4 vs 49.6 mo (HR 0.73); FDA Jan 2025 for previously untreated MCL in patients ineligible for ASCT.
• VR-CAP (Robak NEJM 2015): bortezomib substituted for vincristine in R-CHOP; superior PFS vs R-CHOP in transplant-ineligible patients.
• R-CHOP + rituximab maintenance: option per Kluin-Nelemans NEJM 2012; maintenance R extends PFS/OS in older fit patients.
• Other options: RBAC500 (rituximab, bendamustine, cytarabine); modified R-hyper-CVAD in patients >65; lenalidomide + rituximab.
• Indolent leukemic non-nodal MCL (SOX11−, IGHV-mut, asymptomatic, no high-risk features): watch & wait appropriate.

• Bendamustine precautions: myelosuppression and infection, infusion reactions, tumor lysis syndrome, rash (especially with concomitant allopurinol). Dosing in renal/hepatic dysfunction not fully defined.

Relapsed / Refractory

• Second line, covalent BTKi: acalabrutinib (FDA Oct 2017, ACE-LY-004, Wang Lancet 2018), zanubrutinib (FDA Nov 2019); highly selective, designed to reduce the off-target Afib/bleeding/infection seen with ibrutinib. Ibrutinib (first-in-class BTKi, 560 mg daily; blocks pERK/pJNK/NF-kB and mantle-cell migration/adhesion; AEs include bleeding/bruising ~39%, cardiac arrhythmia, diarrhea, fatigue) was withdrawn for MCL in 2023 after SHINE.
• Lenalidomide + rituximab: immunomodulatory (cereblon binding → ↓ IRF4; T-cell/NK activation, ↑ ADCC). Regimen: lenalidomide 20 mg days 1 to 21 of 28 + rituximab weekly × 4, then maintenance.
• Other second-line options: BR (if not used first line), BR + cytarabine, bortezomib ± rituximab, R-DHAP, R-GemOx.
• Pirtobrutinib (Jaypirca): non-covalent reversible BTKi; FDA Jan 2023 for R/R MCL after ≥2 prior lines including a BTKi (BRUIN, Wang ML JCO 2023; PMID: 37100541), ORR ~58% post-cBTKi.
• Brexucabtagene autoleucel (Tecartus): anti-CD19 CAR-T; FDA Jul 2020 for R/R MCL (ZUMA-2 required prior BTKi, but the label does not) (ZUMA-2, Wang ML NEJM 2020; PMID: 32242358). Real-world data confirmed efficacy (Wang Y JCO 2023; PMID: 36753699).
• Lisocabtagene maraleucel (Breyanzi): FDA May 2024 for R/R MCL after ≥2 lines including a BTKi (TRANSCEND NHL 001 MCL cohort).
• Venetoclax (BCL2 inhibitor): active as monotherapy and in combination (with ibrutinib, rituximab, or Len-R); typically 3rd line; AIM (ven + ibrutinib, Tam NEJM 2018) was in BTKi-naive R/R MCL; post-BTKi venetoclax responses often short-lived.
• Sonrotoclax (Beqalzi): next-generation BCL2 inhibitor; FDA accelerated approval May 2026 for R/R MCL after ≥2 lines including a BTKi (ORR 52%, CR 16%).
• Other: bortezomib ± rituximab (proteasome inhibitor); temsirolimus (mTOR inhibitor, approved in EU); PI3K inhibitors (idelalisib, duvelisib; not FDA approved in MCL; copanlisib and umbralisib withdrawn from US market); bendamustine if not previously given.
• Allo-HSCT: consider for chemo/BTKi/CAR-T-refractory or TP53-mut young fit patients; curative potential in select cases.
• Bispecifics: glofitamab and epcoritamab show emerging activity in R/R MCL; not yet specifically approved.

CNS Disease

• Blastoid variant and high-MIPI patients have ↑ CNS relapse risk. Routine CNS prophylaxis is not standard, but consider it in blastoid/pleomorphic, high Ki-67, or TP53-mutated disease.

High-Yield Pearls

• t(11;14) + cyclin D1+ in a mature B-cell lymphoma = MCL (same finding also in a subset of plasma cell myeloma).
• CD5+ CD23− with bright CD20 distinguishes MCL from CLL (which is CD5+ CD23+).
• Lymphomatous polyposis on colonoscopy = classic for MCL GI involvement.
• Ki-67 drives biology: MCL can range from indolent to aggressive.
• SOX11−, IGHV-mut, leukemic non-nodal = indolent variant; watch & wait.
• TP53-mut: avoid intensive chemo; novel agents + early allo planning.
• Maintenance rituximab improves OS in MCL (unlike FL, where it improves PFS but not OS).
• TRIANGLE: ibrutinib-containing induction is the new standard in younger patients; ASCT no longer mandatory.
• SHINE: ibrutinib + BR in older patients improves PFS but not OS; caution in ≥65.
• Brexu-cel (ZUMA-2): standard 3rd-line for post-BTKi R/R MCL.