Despite characteristics of aggressive lymphoma, very late-onset PTLDs after renal transplantation may respond to conventional chemotherapy. However, because a high rate of infectious complications occurred, new therapeutic strategies, such as combinations of anti-CD20 monoclonal antibodies and lower doses of chemotherapy, are warranted.

The aim of this study is to explore the expression of osteopontin (OPN) and its relationship with prognostic factors and survival in diffuse large B cell lymphoma (DLBCL). A tissue microarray was performed for immunohistochemical evaluation. Contingency tables were analyzed for trends; chi-square test was used to determine differences between groups. Univariate and multivariate Cox proportional hazards-regression analyses were performed to evaluate the impact of prognostic factors on survival. Expression of OPN was observed in 28%. It was different in non-germinal center DLBCL (P=0.04). The mean overall survival (OS) was lower in patients with positive OPN expression (19.762; CI 95% 14.269-25.255) it was not significant (P=0.123). It is not possible to establish a clear relationship between the expression by immunohistochemistry of osteopontin and a poor prognosis but it would be important to complement the analysis with other techniques as PCR or NGS that allow us to assess the influence of the isoforms and post-translational modifications of OPN on the biological behavior of DLBCL. Our findings indicate that OPN expression could be associated with a more aggressive variant of lymphoma: non-germinal center DLBCL.

Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) is a recently recognized highly aggressive malignant proliferation of plasmacytoid dendritic-cell (PDC) precursors which consistently express CD4, CD56 and CD123. Mortality is high despite transplant and the response to treatment is poor, except for preliminary results with conjugated anti-CD123. Clinically, cutaneous involvement is the most common feature with or without the presence of initial bone marrow infiltration, however patients may present with bone marrow-only disease. BPDCN is underdiagnosed, and can be confused with several entities, including acute myeloid leukemia. We describe our experience with 7 cases of BPDCN, their clinical and pathological presentation, and describe possible misdiagnosis and the antibodies that may help in corroborating BPDCN. See table for clinical characteristics at diagnosis. Diagnosis of BPDCN must take into account clinical, morphological and immunohistochemical analysis (IHC), since these tumors variably express markers that may be shared with other neoplasias including CD56 and TCL-1. When IHC is not categorical for BPDCN, the WHO recommends reporting the cases as AML of ambiguous lineage. The typical IHC includes CD4, CD43, CD45RA, CD56, CD123, TCL1, CLA and CD68. The absence of CD56 does not exclude the diagnosis. Markers shared with other hematological tumors include: CD7, CD33, CD2,CD36 and CD38 and TdT. Thus differential diagnosis should be done primarily with A) Skin infiltration by acute myeloid leukemia (myeloperoxidase +, 7- lysozyme +, CD34 +, CD117 +/-) B) Skin Infiltration by T / NK extra nodal lymphoma ( CD8 , cytotoxic cytoplasmic granules [CCG] , granzyme B, perforin, TIA1 and EBER) C) cutaneous peripheral T lymphoma ( +/- CD8, CD2 +/-, +/- CD5, CD7 +/- and variably positive CCG´s). D) Other histiocytic and dendritic cell-neoplasms may also be considered in the differential diagnosis however the histological appearance is usually characteristic. BPDCN is a poorly known entity that should be suspected by both clinician and pathologist in order to make a correct diagnosis. Table Table. Disclosures No relevant conflicts of interest to declare.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a rare condition in which granulomas form in tissues through the accumulation of abnormal histiocytes (Langerhans cells), granulocytes and lymphocytes. Prognosis in patients with disseminated disease has been associated with a chronic course, and a high morbidity and mortality rate. In terms of treatment, etoposide and vinblastine are considered to be the most effective agents in monochemotherapy. Here we report the case of an adult patient with LCH who has improved considerably after treatment with 2-CDA followed by IM. CLINICAL CASE: 37 year-old Hispanic female with history of burning epigastric pain, nausea and vomiting starting in 1998. In 1999 diarrhea and steatorrhea appeared. Whipple disease was diagnosed in another hospital but treatment was unsuccessful. She came to our hospital in 2003, complaining of the aforementioned symptoms plus severe malnutrition. Upper GI endoscopy and colonoscopy were performed and the biopsies showed infiltration with LCH. Bone marrow (BM) biopsy showed LCH infiltration too. CD117 (KIT) expression was investigated both in gastric and BM biopsies, turning out to be highly positive. Therapies and outcomes are shown in table 1. DATE DRUGS TREATMENT DURATION WEIGHT (Kg) ALBUMIN (g/dL) GI ENDOSCOPY BIOPSY Dec/03 VBL/VP-16/PDN 5 cycles 33.5 0.99 Polyps and pseudopolyps Infiltrated by LCH. Sep/05 MTX/PDN 18 mos. 39.5 3.18 Polyps and pseudopolyps Infiltrated. Jul/07 2-CDA 9 cycles 55.3 4.0 Polyps Infiltrated. May/08 IM 6 mos. 57 4.0 Nodular pattern. No polyps Decreased infiltration by LCH CONCLUSIONS: This case illustrates that multisystemic LCH can be successfully treated with, at least two more drug choices: 2-CDA and, in those patients with expression of KIT and/or PDGF, IM.

Background: Bone marrow necrosis (BMN) affects both stromal tissue and hematopoietic precursors and its prevalence ranges from 0.3–37%, being the hematologic malignancies the most frequent cause. Aim: To describe the clinical and pathological characteristics of 30 patients with BMN diagnosed and treated at our institution. Methodology: We included all adult patients diagnosed during the last 8 years (2000– 2007) via bone marrow aspiration and biopsy. Results: Median age was 44 years (range 14–78); 53.3% were females. 42.2% of the patients died within a month mainly due to adult respiratory distress syndrome (ARDS) and septic shock. Just 5 (16.7%) of them are still alive. In all cases, BMN was of coagulative type, and extense in 23 (76.6%) of the patients. The main symptoms were: bone pain (53%), anemia (53%) and fever (50%), whereas the main underlying diseases were: acute lymphoblastic leukemia (ALL) in 26.7%, non-Hodgkin lymphoma (NHL) in 13.3% and multiple myeloma (MM) in 10% of the patients. Conclusions: BMN is associated to a fatal course and to hematologic malignancies in most of our patients.

5132 There is a well- recognized correlation between cancer and aberrant hemostasis. Venous thromboembolism (VTE) in individuals with solid epithelial tumors has been associated with a poor prognosis, with more than three-fold higher risk of early death as compared to cancer patients without thrombosis. The expression of tissue factor (TF), a cell-surface membrane glycoprotein that triggers the activation of coagulation by cancer cells, is one of the main underlying mechanisms linking thrombosis and aggressive tumor behavior. TF is expressed in a variety of solid tumors in association with genetic events affecting oncogenes and tumor suppressor genes. However, the mechanisms of thrombosis in individuals with hematological malignancies may differ from those with solid tumors. We have previously shown that despite the high rate of thrombosis in multiple myeloma, malignant plasma cells only rarely express TF. We sought to determine TF gene (F3) and protein expression in hematological neoplasias. F3 expression profiling was studied on a variety of cell lines established from lymphoid and myeloid neoplasias available at Glaxo Smith Kline (GSK) Cancer Cell Line Genomic Profiling Dataset (https://array.nci.nih.gov/caarray/project/woost-00041). Interestingly, F3 expression was absent in all lymphoid neoplasias studied, in sharp contrast to acute myeloid leukemias (AML) and solid tumors, of which 30 and 90% expressed F3, respectively. Immunohistochemistry (IHC) confirmed the absence of TF protein expression in all indolent and high-grade B-cell lymphomas (99 patients, including germinal center and activated B-cell phenotype diffuse large B-cell lymphomas) and in all T-cell lymphomas/leukemias (20 patients) studied. IHC for TF was also negative in AML (11 patients) but positive in representative solid tumors (breast, pancreas, prostate), except for renal cell carcinoma which has been previously shown to lack TF. We propose that the pathogenesis of VTE associated with hematological neoplasias differs from that of solid tumors. Though TF from non-neoplastic cell sources may still be important for the prothrombotic state often seen in these patients, we show there is no evidence for a role of tumor-derived TF in the development of DVT, nor in neoplastic behavior. Thus, treatments directed against TF may not impact on prognosis in lymphoid, and non TF-expressing myeloid neoplasias. Disclosures: No relevant conflicts of interest to declare.

Lymphomatoid granulomatosis is a very rare B cell lymphoproliferative disease associated with Epstein-Barr virus infection. It is related to states of immunosuppression and affects the lung in more than 90% of cases, forcing the clinician to establish a differential diagnosis with other diseases such as infections, Wegener's granulomatosis, lymphoma, or lung metastases. There is no standard treatment for this disease. In this paper, we describe a rare case of a patient with grade 3 lymphomatoid granulomatosis with newly diagnosed HIV infection who started antiretroviral treatment with a gradual improvement of the lesions.

Background: Defining the extent of disease is essential for determining the prognosis and management of patients with Hodgkin (HL) and non-Hodgkin lymphoma (NHL) as the presence of advanced disease, including involvement of an extralymphatic site, is associated with inferior outcomes (Cheson et al, 2014). 18F-fluorodeoxyglucose positron emission tomography (FDG PET-CT) has an excellent diagnostic performance for evaluation of bone marrow infiltration (BMI) in patients with lymphoma but it is expensive and not always available at low and middle-income health care facilities. Unilateral bone marrow biopsy (BMB) is a more accessible test and has been the standard to identify lymphomatous BMI. Unfortunately, it is an unpleasant procedure for the patient and can be limited by technical constraints. The aim of this single-center retrospective cohort study was to evaluate the diagnostic performance of FDG PET-CT for BMI in lymphoma patients, comparing it with BMB as the gold standard. Also, we evaluated for discordant results between both studies along with its effect on patient treatment. Methods: Newly diagnosed lymphoma patients evaluated at the National Cancer Institute between July 2017 and December 2018 were identified from our institutional lymphoma data base. Five hundred patient files were reviewed for bone marrow evaluation at diagnosis by BMB and FDG PET-CT as well as for other clinical characteristics. Only 355 patients had both FDG PET-CT and BMB performed and adequately reported, so the rest were excluded from the analysis. Fisher's exact and Pearson Chi-square tests were used to compare categorical variables. Comparisons of continuous variables were performed using Mann-Whitney U test. Setting BMB as the gold standard, diagnostic performance of FDG PET-CT for detecting BMI was evaluated. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive and negative likelihood ratios (LR) and accuracy were calculated for the most common histological subtypes. Logistic regression model was used for univariate and multivariate analysis of predictors for positive BMB and positive FDG PET-CT for BMI. Results: The most common histologic type was diffuse large B-cell lymphoma (DLBCL) in 42.4% of cases, followed by HL in 20.4%, and follicular lymphoma (FL) in 11.2%. Median age was 53 years. B symptoms were present in 59.6% of cases and 71.4% debuted with advanced stage of disease (Ann Arbor III and IV). BMB was positive in 17% of all patients and 28% had a positive FDG PET-CT for BMI (Table 1). BMB was positive in 17.2% of HL, 12.3% of DLBCL, 29.8% of FL and 15.6% of other types of lymphoma patients. Overall, sensitivity of FDG PET-CT was 74.1%, specificity 80.1%, PPV 42.2%, NPV 94.1%, +LR 3.73, -LR 0.32 and accuracy 79.2%. The diagnostic performance of FDG PET-CT in patients with HL, DLBCL, FL and other types of lymphoma is shown in Table 2. As for predictors for BMB positivity, the presence of B symptoms, neutropenia and thrombocytopenia were independent factors for BMI with adjusted OR of 2.44, 95% CI (1.19, 4.99), 5.64, 95% CI (1.32, 24.08) and 4.12, 95% CI (1.66, 10.26), respectively. For positive FDG PET-CT, the presence of B symptoms, thrombocytopenia and advance stage remained significant with adjusted OR of 2.96, CI 95% (1.73, 5.05), 2.75, 95% CI (1.17, 6.48) and 19.22, 95% CI (5.90, 62.66), respectively. Seventy-four patients had discordant results between BMB and FDG PET-CT. The discrepancy in BMB and FDG PET-CT results did not have an effect on treatment. Conclusions: In addition to international clinical practice guidelines recommendations, in our center we recommend performing a BMB to those patients with HL and FDG PET-CT negative for BMI who present with cytopenias and B symptoms at the time of diagnosis. For patients with DLBCL our FDG PET-CT sensitivity was lower than expected, so we recommend a complementary BMB to all DLBCL patients with a positive FDG PET-CT for BMI (stage IV) that otherwise would be early stages (I and II) and would benefit from less aggressive therapy. In all other NHL including FL, we recommend performing a unilateral BMB with immunohistochemical analyses and flow cytometry, if available, for initial evaluation of BMI. Still in the absence of FDG PET-CT, a whole-body contrast-enhanced CT along with a unilateral posterior iliac crest BMB could adequately stage most types of lymphoma at low and middle-income health care facilities. Disclosures No relevant conflicts of interest to declare.