In 2008, the MIPI scoring criteria were established to enable the stratification of clinically diverse MCL patients into three risk groups: low risk, intermediate risk and high risk The MIPI criteria include the following 4 independent pre-treatment prognostic factors: age, Eastern Cooperative Oncology Group performance status, pre-treatment ratio of actual/upper limits of normal for lactate dehydrogenase (LDH), and pre-treatment white blood cell (WBC) counts [
7]. In this report, patients with a score of 3 or less were said to have indolent disease and could defer therapy for a median of 1 year. Moreover, once these patients began therapy, the patients showed more sensitivity to treatment, with a 5-year median survival of 60%. This risk model has been validated in other retrospective and prospective clinical publications [
8,
9]. In addition to these variables, tumor proliferation is recognized as one of the strongest biological prognostic factors in MCL, and high tumor cell proliferation indicates shorter survival [
10]. In order to predict MCL survival, a mathematical model was established [
11]. The quantitative model combining 20 different expression levels of proliferation genes in MCL was used to determine the extent of proliferation. The proliferation signature average was inversely correlated with survival with high statistical significance not only in the training set (
p = 1.92X10
−5) but also in the validation set (
p = 7.44 X10
−5). Additionally, this signature average was correlated with the number of Ki67-positive cells (
r = 0.69), which is an immunohistochemistry (IHC) marker of proliferative index. The IHC Ki-67 data is not as strong but is readily available in clinical practice and also correlated with OS [
12,
13]. Hoster et al. reported that significant differences in time to treatment failure (64 months versus 19 months) and overall survival (OS) (not reached versus 45 months) were found between the Ki-67 level < 30% group versus the Ki-67 level ≥ 30% group in 543 MCL cases (
p < 0.0001 each) [
12]. Later, the Ki-67 index and MIPI were combined and modified to create the MIPI-c. This newer scoring criteria separated four groups of 508 patients with the following varying 5-year OS rates: 85, 72, 43, and 17% (
P < .001) and was more discriminative than the MIPI criteria alone [
14]. We believe that the MIPI-c scoring system should be used to diagnose SMCL, with SMCL scored as a low MIPI score ≤ 3 and a Ki-67 index <30%.
Table 1
Comparison of clinical, morphology, immunophenotype and genetics features between SMCL and classic MCL
Clinical features |
B symptom | without | with or without |
Serum LDH | normal | elevated or normal |
Serum β2-MG | normal | elevated or normal |
MIPI | low risk | low to high risk |
Ki-67 | < 30% | ≥30% |
Max tumor diameter | < 3 cm | ≥3 cm |
SUV of PET/CT | ≤ 6 | > 6 |
evaluation every 3 mons | no tumor growth | having tumor growth |
Morphology |
Origin | germinal or post-germinal center | antigen-naïve pregerminal center |
Cytology | non-blastoid/pleomorphic | small cell, classic, pleomorphic, or blastic |
Immunophenotype |
CD5 | low | high |
CD38 | low | high |
CD23 | high | low |
CD200 | high | low |
light chain restriction | kappa | lambda |
Genetics |
TP53
| low | high |
NOTCH1/2
| low | high |
C-myc
| low | high |
Cyclin D1 mRNA | low | high |
Cell cycle | G1 or before | S |