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Background Multiparameter flow cytometry allows the detection of minor monoclonal B-cell populations. Using this technique combined with morphology, we were struck by the presence of minor populations of small monoclonal B cells in bone marrows of patients with diffuse large B-cell lymphoma in routine diagnostic samples and performed a systematic retrospective study.Design and Methods Bone marrows of 165 patients with primary diffuse large B-cell lymphoma without histological evidence of concurrent non-Hodgkin’s lymphoma were studied by routine microscopy of trephines and smears, immunohistochemistry and multiparameter flow cytometry.Results Diffuse large B-cell lymphoma infiltration in marrows was documented in 11 of 165 patients. Morphological examination consistently revealed a higher tumor load than evidenced by flow cytometry. Of interest, only 3 of 119 patients with diffuse large B-cell lymphoma not otherwise specified, the largest subtype, showed marrow infiltration. By contrast, flow cytometry revealed a minor monoclonal B-cell population in 24 of 165 patients, none of whom showed diffuse large B-cell lymphoma infiltration by morphology. Of interest, morphological examination revealed the presence of small B cells in the marrows of those patients. Moreover, 11 of 39 (28.2%) of patients with diffuse large B-cell lymphoma not otherwise specified of ABC subtype and only 3 of 80 (3.7%) with the GCB subtype showed these monoclonal small B cells (P=0.0002). In addition 4 of 8 (50%), 4 of 15 (26.7%) and 2 of 3 (66.7%) patients with primary testicular, primary central nervous system and leg-type diffuse large B-cell lymphoma, respectively, showed monoclonal small B cells.Conclusions Bone marrow infiltration with diffuse large B-cell lymphoma in patients with diffuse large B-cell lymphoma not otherwise specified is rare at diagnosis. By contrast, a high number of diffuse large B-cell lymphoma not otherwise specified of the ABC subtype but not of GCB subtype is associated with monoclonal small B cells in the marrow. Whether these monoclonal small B cells are precursors of diffuse large B-cell lymphoma of the ABC type or arise in a common background that favors clonal B-cell expansion remains to be demonstrated.

Transdifferentiation of B cell lymphoma of germinal center cell origin to histiocytic sarcoma has recently been described but is a rare occurrence. The cause for loss of B cell differentiation in these lymphomas is unknown. We investigated whether somatic hypermutation of the PAX-5 gene, a transcription factor that is important for maintaining B cell identity and is frequently mutated in B cell lymphomas of germinal center cell origin, might be a cause for loss of PAX-5 expression and thus B cell phenotype. However, no somatic hypermutation of the PAX-5 gene was detected in the two cases we studied. The molecular basis for transdifferentiation of B cell lymphoma to histiocytic sarcoma remains therefore unresolved.

Granulomatous slack skin is a rare cutaneous T-lymphoproliferative disease characterized by pendulous skin folds. Histology typically reveals a dermal infiltrate of T cells and multinucleated giant cells showing elastophagocytosis. Specific genetic abnormalities have not yet been identified. Currently, granulomatous slack skin is classified according to the World Health Organization classification as a variant of mycosis fungoides although supporting genetic evidence is yet lacking. We present a well-documented case of a 46-year-old man with the typical histologic and clinical findings of granulomatous slack skin. Cytogenetic analysis of a skin biopsy revealed a t(3;9)(q12;p24) as the sole chromosomal abnormality. Fluorescence in situ hybridization analysis did not reveal involvement of the JAK2 gene, located at chromosome band 9p24, and previously shown to be amplified in Hodgkin lymphoma and primary mediastinal diffuse large B-cell lymphoma. Although more cases have to be reported and the putative oncogene involved in the translocation has yet to be identified, the cytogenetic findings are unlike those described for mycosis fungoides and suggests that granulomatous slack skin is a distinct primary cutaneous T-cell lymphoma.

Peripheral T-cell lymphoma (PTCL) with a nodular architecture is rare. Recently, two variants have been described with infiltration of the B-cell follicle, one variant that localizes to the marginal zone with a so-called perifollicular growth pattern, and a variant that localizes to the germinal center. These lymphomas have a CD4+ phenotype and may express Bcl-6. We have studied five similar cases of PTCL with involvement of the B-cell follicle. However, our cases differ from the cases previously described by their predominant and frequently patchy involvement of the expanded mantle zone of the B-cell follicle at onset. Later biopsies in three of the cases show diffuse infiltration of the lymph node, without features of angioimmunoblastic TCL (AILT). All cases expressed Bcl-6 in addition to CD4. Cytogenetics was available in four of the cases but revealed no recurrent chromosomal aberrations or changes associated with other types of PTCL. No mutations of the BCL-6 gene were observed. Together, the cases seem to have an intermediately aggressive clinical behavior. Whether our cases are part of a spectrum of PTCLs that encompasses previously described variants with predominant marginal zone or germinal center infiltration or they represent a separate T-cell lymphoma type remains to be demonstrated by a study of more of such cases.

Summary Previously, we have shown that patients with diffuse large B-cell lymphoma (DLBCL) transplanted with contaminated bone marrow (BM) generally have a poor outcome. Whether this is also the case when peripheral blood progenitor cell (PBPC) grafts are used is not known. Forty-three patients with chemosensitive DLBCL or follicular lymphoma grade 3 (FLgr3) were treated with high-dose therapy (HDT) and autologous stem cell support. Nine patients received purged grafts. Quantitative real-time polymerase chain reaction (QRT-PCR) for either the BCL2/IgH translocation or allele specific oligonucleotide (ASO) QRT-PCR for the immunoglobulin heavy chain (IgH) complementarity-determining region 3 were used. Nine of 25 (36%) PBPC grafts contained tumour cells as tested by QRT-PCR, including two grafts purged by CD34 + cell enrichment combined with B-cell depletion. The level of contamination of the PBPC/CD34 + cells ranged from 0 to 8AE28%. No relationship could be shown between the total number of tumour cells infused and relapse. Patients receiving PCR-positive or PCR-negative PBPC grafts had similar progression-free survival (PFS) (P ¼ 0AE49). However, a significant difference was seen in PFS and overall survival (OS) for the patients given ‡6AE1 · 10 6 CD34 + cells/kg compared with those given