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Summary. Biopsies from 319 haematopoietic neoplasms were immunostained for intracellular leucocyte-specific protein 1 (LSP1) to assess its distribution and to compare its diagnostic value with that of CD45 (leucocyte common antigen: LCA). Most small B-cell neoplasms expressed LSP1, but one third of diffuse large B-cell lymphomas (DLBCL) were LSP1 negative. Among the cases with DLBCL (76 samples) tested for both LSP1 and CD45, one fifth expressed only CD45, but five samples were LSP1-positive and negative for CD45. The latter pattern was also seen in four of nine myelomas. Five out of 14 T-lymphoblastic lymphomas co-expressed LSP1 and CD45, and three cases were LSP1 negative and CD45-positive. Most peripheral T-cell lymphomas co-expressed LSP1 and CD45. All anaplastic lymphoma kinase (ALK)-negative lymphomas of anaplastic large cell morphology (T and null phenotype) expressed LSP1 although the percentage of LSP1-positive tumour cells was variable, however, only seven out of 30 cases with ALK-positive lymphoma were LSP1 positive. LSP1 was expressed on Reed–Sternberg cells in 60 out of 66 cases with classic Hodgkin's disease but neoplastic cells were usually negative in lymphocyte predominant Hodgkin's. This study confirms the wide expression of LSP1 within haematopoietic neoplasms and its diagnostic value for a minority of lymphoid tumours that have lost CD45 expression. Furthermore, the strong expression of LSP1 in classic Hodgkin's disease, contrasting with its heterogeneous expression in ALK-negative anaplastic lymphomas, may help to distinguish the latter lymphomas from patients with tumour cell-rich Hodgkin's disease. [ABSTRACT FROM AUTHOR]

Tumour-associated macrophages (TAMs) have been associated with survival in classic Hodgkin lymphoma (cHL) and other lymphoma types. The maturation and differentiation of tissue macrophages depends upon interactions between colony-stimulating factor 1 receptor (CSF1R) and its ligands. There remains, however, a lack of consistent information on CSF1R expression in TAMs. A new monoclonal antibody, FER216, was generated to investigate CSF1R protein distribution in formalin fixed tissue samples from 24 reactive lymphoid tissues and 187 different lymphoma types. We also analysed the distribution of CSF1R+, CD68+ and CD163+ macrophages by double immunostaining, and studied the relationship between CSF1R expression and survival in an independent series of 249 cHL patients. CSF1R+ TAMs were less frequent in B-cell lymphocytic leukaemia and lymphoblastic B-cell lymphoma than in diffuse large B-cell lymphoma, peripheral T-cell lymphoma, angioimmunoblastic T-cell lymphoma and cHL. HRS cells in cHL and, with the exception of three cases of anaplastic large cell lymphoma, the neoplastic cells in NHLs, lacked detectable CSF1R protein. A CSF1R+ enriched microenvironment in cHL was associated with shorter survival in an independent series of 249 cHL patients. CSF1R pathway activation was evident in the cHL and inactivation of this pathway could be a potential therapeutic target in cHL cases. [ABSTRACT FROM AUTHOR]

The OX-TES-4 antigen originally elicited an antibody response in 50% of diffuse large B-cell lymphoma (DLBCL) patients but not in control subjects. OX-TES-4 is encoded by a novel gene, MORC4, located at chromosome Xq22.3. The MORC4 protein contains a HATPase-c domain, CW zinc finger motif, nuclear localisation signals and a nuclear matrix-binding domain, together with a coiled-coil region. MORC4 mRNA is widely expressed at low levels in normal tissues, showing highest expression levels in placenta and testis. mRNA levels were increased in non-germinal centre-derived DLBCL and Hodgkin lymphoma cell lines, compared with germinal centre-derived DLBCL cell lines and normal B cells. Nineteen DLBCL patients (66%) expressed significantly higher levels of MORC4 mRNA than normal B cells ( P = 0·0031). The differential expression of MORC4 identifies this molecule as a potential lymphoma biomarker, whose overexpression may contribute to the immunological recognition of MORC4 by a subgroup of DLBCL patients. [ABSTRACT FROM AUTHOR]