—  SPECIALTY CONFERENCE  —

Hematopathology

Case 3 - Mantle Cell Lymphoma, Small Cell Variant, with a Very Indolent Clinical Behavior

Elias Campo, M.D.
Hospital Clinic, University of Barcelona
Barcelona, Spain





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Clinical History
78 year-old female with a 10-year history of a low grade, leukemic, B-cell neoplasm, initially diagnosed in 1995 as chronic lymphocytic leukemia [stage A(0)]. In December 2003, a stage I renal cell adenocarcinoma was resected without complication. At the end of 2004, she developed progressive lymphocytosis, anemia, and thrombocytopenia and was referred to our hospital for splenectomy. Physical examination was normal with the exception of the splenomegaly. Laboratory tests demonstrated normal LDH levels, B2 microglobulin 6.2 mg/L (normal 0-2.3) WBC 123.40 x103/µL (lymphocytes 85%), RBC 2.88 x106/µL, Hgb 8.7 g/dL, HCT 29%, MCV 89.7 fL, platelets 119 x103/µL. Flow cytometry of the peripheral blood showed a clonal lymphoid proliferation positive for CD19, CD79b, CD20 (bright), CD22, CD23 (66% of all B-lymphocytes), FMC7, IgM/IgD, kappa (bright) and negative for CD5, CD43, CD10. The general status of the patient improved after the splenectomy, but the lymphocytosis persisted. She did not receive additional treatment for two years, until July 2007, when because of progressive lymphocytosis she again received cyclophosphamide for 6 months. The patient is currently alive with clinically stable disease.


Case 3 - Slide 1
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Case 3 - Figure 1
The histological section of the spleen shows an expansion of the white pulp with a diffuse lymphoid infiltrate in the red pulp
Case 3 - Figure 2
Some nodules of the white pulp had a hyalinized aspect. The nodules were not very well demarcated, and the lymphoid cells of merged with the infiltrate of the red pulp.
Case 3 - Figure 3
A small reactive germinal center could be recognized in occasional white pulp nodules.

Case 3 - Figure 4
The tumor cell infiltrate was composed of small lymphoid cells with round nuclei, dense chromatin and scant cytoplasm.
Case 3 - Figure 5
The tumor cells had a monotonous morphology with round nuclei and dense chromatin without prominent nucleoli. No plasmacytoid differentiation could be seen.
Case 3 - Figure 6
The tumor cells were strongly positive for CD20 with a similar intensity in all the areas.

Case 3 - Figure 7
CD3 staining revealed few scattered lymphoid cells, but the tumor cells were negative.
Case 3 - Figure 8
CD5 staining was positive only in few lymphocytes with a similar distribution to that of the CD3 positive cells. Some of these cells tended to be at the periphery of the white pulp nodules. The tumor cells were negative.
Case 3 - Figure 9
CD5 positivity is present in residual lymphoid cells, but tumor cells are negative.

Case 3 - Figure 10
IgD staining shows the diffuse positivity of the tumor cells.
Case 3 - Figure 11
Cyclin D-1


Histology
The histological sections of the spleen revealed a nodular expansion of the white pulp with a monotonous lymphoid proliferation of small lymphocytes with round nuclei, dense chromatin, and scant cytoplasm. The boundaries of most nodules were not well defined and the tumor cells tended to merge with the cells in the red pulp. Clear germinal centers were only rarely seen and they were small and well delineated and preserved. The red pulp was extensively infiltrated in the sinusoids and cords by a similar population of lymphoid cells with a diffuse pattern. Mitotic figures were very rare.

Immunophenotype
The immunophenotype of the tumor cells was examined by flow cytometry of splenic cell suspensions and immunohistochemistry of the histological sections. The flow cytometry confirmed the phenotype observed in the peripheral blood and also showed that CD25, CD11c, and CD103 were negative. The immunostaining also demonstrated that the tumor cells were positive for CD20, CD23, IgM, and IgD with kappa restriction but negative for CD5, CD43, CD10, BCL-6, and IRF4/MUM1. CD23 and CD21 revealed a meshwork of follicular dendritic cells in the white pulp nodules indicating the existence of lymphoid follicles that were overrun by the neoplastic cells. Cyclin D1 was strongly positive in the nucleus of virtually all tumor cells. Ki67 was positive in less than 10% of the cells.

Genetic studies
A conventional cytogenetic study of the splenic cell suspension revealed the translocation t(11;14)(q13;q34) as a single alteration without additional chromosomal aberrations.

Final Diagnosis
Mantle cell lymphoma, small cell variant, with a very indolent clinical behavior

Comments
The clinical, morphological and phenotypic features of this lymphoid neoplasm are very uncommon and the diagnosis not easy to establish. This case raises several questions on the classification of the tumor and the practical management of the patient. The differential diagnosis includes atypical chronic lymphocytic leukemia (CLL), splenic marginal zone lymphoma (SMZL), lymphoplasmacytic lymphoma, splenic B-cell lymphoma, unclassifiable, and mantle cell lymphoma (MCL). Although the diagnosis of hairy cell leukemia may be entertained, it can easily be ruled out because of the distinct phenotype and morphological features.

The patient had been initially diagnosed as a CLL in a community hospital based on the B-cell lymphocytosis. After a long indolent clinical course of 10 years, the patient was referred to our center because of progression of the disease with splenomegaly. The studies in our center showed that the morphology of the peripheral blood cells was not typical for CLL because some cells showed clear cytoplasm and 4% had villous prolongations suggesting a splenic marginal zone lymphoma. The flow cytometry study of the peripheral blood showing negativity for CD5 and strong expression of CD20 and surface Ig argued also against CLL. CD23, however, was positive. The histological morphology was not consistent with a CLL diagnosis because the tumor cells were monotonous and no prolymphocytes or paraimmunoblasts were observed. The diagnosis of lymphoplasmacytic lymphoma might be considered but the lack of plasmacytoid differentiation and strong immunoglobulin staining help to exclude the diagnosis.

The diagnosis of SMZL was strongly considered. The clinical presentation with a long clinical history, splenomegaly, and absence of lymphadenopathy, the presence of some villous lymphocytes and the phenotype were consistent with this diagnosis. However, the histological examination showed a monotonous proliferation of small B-cells without the typical biphasic morphology of small and large B-cells surrounding and infiltrating reactive germinal centers. The infiltration of the red pulp was more diffuse that the typical micronodular pattern observed in SMZL.

We were considering the diagnosis of a splenic B-cell lymphoma, unclassifiable when the cytogenetic study revealed a t(11;14)(q13;q34) translocation. This result prompted us to perform a cyclin D1 staining that was strongly positive. We confirmed also the presence of the translocation in the tumor cells by FISH. This finding made us consider the diagnosis of MCL. The CD5 negativity and CD23 positive phenotype are atypical for this diagnosis, but both aspects have been recognized in around 10% of otherwise typical MCL. [1, 2, 3, 4] However, the most unusual aspect was the long indolent clinical history of the patient. The case was discussed with the clinicians and no additional chemotherapy was given to the patient after the splenectomy due to the previous indolent evolution. She remained with a relatively stable lymphocytosis the following 25 months when she was treated with cyclophosphamide for 12 months and later discontinued. She has been asymptomatic with stable disease for the last six months.

The diagnosis of MCL in a patient with such a stable and indolent disease opens several questions: 1) Does indolent MCL really exist or is this particular case an unusual anecdote? 2) Are those cases real MCL or do they correspond to other ly mphoid neoplasms with an aberrant genotype? 3) If they are MCL, what are the differences between this indolent and conventional MCL with more aggressive clinical behavior?

Does Indolent MCL Exist?
Mantle cell lymphoma is considered an aggressive lymphoid neoplasm with a median patient survival between 3-5 years. However, most series have recognized a relatively broad variability in the outcome with some patients having a rapid course and survival shorter than one year whereas others may have long survival of more than 7-8 years. This variability has been mainly related to the proliferation rate of the tumors. Most parameters associated with poor outcome seem to be surrogate markers of high proliferation such as morphologic variants (blastoid) and several genetic and molecular alterations. [2, 3, 4]

This conventional view of MCL was challenged by the study of Orchard et al [5] that recognized a subgroup of patients with leukemic disease and absence of peripheral lymphadenopathy that showed a more heterogeneous clinical behavior. Some of these patients had a clinically aggressive disease but 24% of them (nine patients) never required treatment for a mean of 58 months (range 8-175 months) and in a further nine, therapy was delayed because of stable disease with a mean of 29 months (range 10-60 months). The median survival of this group was significantly longer (79 months) than that of patients presenting with a conventional nodal disease (30 months). These finding strongly support the idea that some MCL presenting with non-nodal disease may have a very indolent clinical course. Our case had a clinical presentation and evolution similar to this group of non-nodal MCL patients.

A second strong evidence favoring the existence of MCL with a very indolent clinical course are the reports of two patients with subclinical peripheral blood and minimal nodal involvement by a lymphoid neoplasm interpreted as MCL because of the identification of the t(11;14) translocation and the expansion of the mantle zone of the follicles by a cyclin D1 positive lymphoid neoplasm. [6, 7] These patients had stable and asymptomatic disease for more than 5 and 12 years, respectively. Two other studies have reported four patients presenting with a similar expansion of the mantle zone area by cyclin D1 positive lymphocytes. [8, 9] This limited involvement of the lymph nodes has been named "in situ" MCL. Unfortunately, the clinical follow up of these patients is scarce but at least one of them was asymptomatic and with no treatment for four years. [8] One patient had disseminated disease at diagnosis and was treated with conventional protocols and an additional patient had progressive disease one year after the diagnosis. [9]

We have recently studied 12 patients with a B-cell neoplasm carrying the t(11;14) and cyclin D1 overexpression that had a stable disease without requiring polychemotherapy for more than 24 months (median 70 months, range 25-121). [10] Five patients were treated only with splenectomy. One of them is the patient presented here. Eleven of these patients presented with peripheral blood involvement but only four had lymphocytosis (> 5x109/L) One patient had a single large lymph node with no evidence of disease in the blood for more than five years.

These observations clearly indicate that a subset of patients with MCL may follow a very indolent and stable clinical course without need of chemotherapy for several years. Most of them seem to present without lymphadenopathy or limited nodal disease. However, two key questions are whether these lymphoid neoplasms are really MCL or do they correspond to other B-cell neoplasms and how can we distinguish at diagnosis these indolent MCL variants from more aggressive conventional tumors.

Are Indolent MCL Real MCL?
Early studies had identified the t(11;14) translocation in several B-cell neoplasms in addition to MCL. Thus some atypical CLL, around 50% of B-PLL and occasional splenic lymphoma with villous lymphocytes were considered to carry this translocation. [2, 3] Subsequent reevaluation of these cases had considered all these tumors as morphological variants of MCL. [11, 12] Similarly, Orchard et al considered that the non-nodal MCL with indolent clinical behavior had the same clinical and pathological features as conventional MCL in terms of age, gender, splenomegaly and gastrointestinal tract involvement, and morphology. None of the indolent cases had typical morphology of CLL, SMZL, or B-PLL. [5]

To further answer this question we have performed a microarray expression profile of seven of our clinically indolent MCL and compared the results with 15 conventional MCL, 15 CLL, 7 FL, 4 SMZL, 3 HCL and 2 hairy cell leukemia variant (HCLv). Interestingly, an unsupervised hierarchical clustering analysis showed that the indolent MCL clustered together with conventional MCL whereas CLL, FL and SMZL/HCL/HCLv clustered in different groups according to the respective diagnosis. [10] These findings strongly suggest that indolent MCL belongs to the same entity as conventional MCL.

How Can We Distinguish at Diagnosis the Indolent MCL from Conventional More Aggressive Tumors?
This question is difficult to answer with the current available information. Most patients that have followed an indolent clinical course have presented with absence of or limited nodal disease and most of them, but not all, had peripheral blood involvement. Some patients had splenomegaly and leukemic presentation. However, these clinical aspects may not be sufficient to suggest that the patient may follow an indolent clinical course since around 20% of patients with a non-nodal disease died in the first year after the diagnosis. [5]

Non-nodal MCL have hypermutated (less than 98% homology) IG genes more frequently than conventional MCL. [5] Contrary to CLL, the mutational status of the IG genes has not been of prognostic significance in most studies in MCL. [13, 14, 15] However, the patients with longer survival in the Orchard study [5] had IG genes with somatic hypermutations. The two indolent MCL described by Nodit et al [6] and Espinet et al [7] also had highly mutated IG genes. In our study the eight indolent MCL in which the IG status could be examined showed a high level of somatic mutations (<95% homology) whereas this number of mutations was only seen in three of the 15 conventional MCL.

Conventional MCL has complex chromosomal karyotypes whereas in the non-nodal MCL the t(11;14) translocation was the only genetic alteration in approximately 50% of the cases. In our study, we have examined the genomic alterations using the 500K Affymetrix SNP array. Only two of the seven indolent MCL had one single additional chromosomal aberration that also occurred in regions not commonly involved in these lymphomas whereas complex karyotypes (more than two aberrations in addition to the t(11;14)) occurred in 12 of the 15 conventional MCL.

Although these observations are still limited they suggest some cases of MCL may have a stable and indolent clinical course. These patients may present most commonly with absent or limited nodal disease, carry a high load of IG gene somatic hypermutations and have very simple karyotypes in which the t(11;14) translocation may be the only chromosomal aberration. More studies are needed to define the clinicopathological features of this MCL subtype to avoid overtreatment of patients that may not require aggressive polychemotherapy for a long period of time.

Take Home Points
  • Leukemic small B-cell neoplasms encompass a variety of tumors with overlapping morphological and phenotypic features. The differential diagnosis of these entities requires a thorough characterization of the morphology, phenotype, and genetic alterations.

  • Although most mantle cell lymphomas have an aggressive clinical evolution with a median survival of 3-5 years, some patients may follow an indolent clinical course with very stable disease without the need of polychemotherapy for many years.

  • MCL with an indolent clinical course usually presents with absence of or limited nodal disease, highly hypermutated IG genes and very simple karyotypes in which the t(11;14) translocation is frequently the only alteration.

References
  1. Liu Z, Dong HY, Gorczyca W et al. CD5- mantle cell lymphoma. Am J Clin Pathol 2002; 118:216-224.

  2. Campo E, Raffeld M, Jaffe ES. Mantel cell lymphoma. Sem Hematol 1999; 36:115-27.

  3. Swerdlow SH, Williams ME. From centrocytic to mantle cell lymphoma: a clinicopathologic and molecular review of 3 decades. Hum Pathol. 2002;33:7-20.

  4. Jares P, Campo E. Advances in the understanding of mantle cell lymphoma. Br J Haematol. 2008; 142: 149 – 165.

  5. Orchard J, Garand R, Davis Z, Babbage G, Sahota S, Matutes E et al. A subset of t(11;14) lymphoma with mantle cell features displays mutated IgVH genes and includes patients with good prognosis, nonnodal disease. Blood 2003; 101:4975-4981.

  6. Nodit L, Bahler DW, Jacobs SA, Locker J, Swerdlow SH. Indolent mantle cell lymphoma with nodal involvement and mutated immunoglobulin heavy chain genes. Hum Pathol 2003; 34:1030-1034

  7. Espinet B, Sole F, Pedro C, Garcia M, Bellosillo B, Salido M et al. Clonal proliferation of cyclin D1-positive mantle lymphocytes in an asymptomatic patient: an early-stage event in the development or an indolent form of a mantle cell lymphoma? Hum Pathol 2005; 36:1232-1237

  8. Richard P, Vassallo J, Valmary S, Missoury R, Delsol G, Brousset P. "In situ-like" mantel cell lymphoma: a report of two cases. J Clin Pathol 59:995-996.

  9. Bassarova A, Tierens A, Lauritzsen GF, Fossa A, Delabie J. Mantle cell lymphoma with partial involvement of the mantel zone: an early infiltration pattern of mantle cell lymphoma?. Virchows Arch 2008; 453: 407-411.

  10. Fernandez V, Salamero O, Jares P et al Hypermutation of Immunoglobulin Genes and a Low Genomic Instability Define a New Subtype of Mantle Cell Lymphoma with Very Indolent Outcome. Abstract LS18; J Hematopathol. 2008; 1:161-256.

  11. Ruchlemer R, Parry-Jones N, Brito-Babapulle V, Attolico I, Wotherspoon AC, Matutes E et al. B-prolymphocytic leukaemia with t(11;14) revisited: a splenomegalic form of mantle cell lymphoma evolving with leukaemia. Br J Haematol 2004; 125:330-336.

  12. Savilo E Campo E, Mollejo M et al. Absence of cyclin D1 protein expression in splenic marginal zone lymphoma. Mod Pathol 1998; 11:601-606.

  13. Thorselius,M., Walsh,S., Eriksson,I., Thunberg,U., Johnson,A., Backlin,C., Enblad,G., Sundstrom,C., Roos,G., & Rosenquist,RSomatic hypermutation and V(H) gene usage in mantle cell lymphoma. Eur.J.Haematol., 2002; 68: 217-224.

  14. Camacho,F.I., Algara,P., Rodriguez,A. et al Molecular heterogeneity in MCL defined by the use of specific VH genes and the frequency of somatic mutations. Blood 2003; 101: 4042-4046.

  15. Cogliatti,S.B., Bertoni,F., Zimmermann,D.R., Henz,S., Diss,T.C., Ghielmini,M., & Schmid,U. IgV H mutations in blastoid mantle cell lymphoma characterize a subgroup with a tendency to more favourable clinical outcome. J.Pathol. 2005; 206, 320-327.