Identification of CD5/SOX11 double-negative pleomorphic mantle cell lymphoma.

Cyclin D1 protein-positive diffuse large B cell lymphoma (DLBCL) has an immunophenotype of CD5(-) cyclin D1(+) SOX11(-), and most cases lack a CCND1 rearrangement and have a gene expression profile of DLBCL. Rarely, cyclin D1 protein-positive DLBCL harbors a CCND1 rearrangement, and some genetic copy number features typical of mantle cell lymphoma (MCL) have been detected. Since gene expression studies have not been performed, whether such CCND1-rearranged cases represent cyclin D1 protein-positive DLBCL or CD5/SOX11 double-negative pleomorphic MCL remains unclear. To date, no cases of CD5/SOX11 double-negative MCL have been reported. In this study, we collected eight cases initially diagnosed as cyclin D1 protein-positive DLBCL, including four with a CCND1 rearrangement and four without. Immunohistochemically, all four CCND1-rearranged cases had >50% of tumor cells positive for cyclin D1 protein, whereas only one (25%) non-rearranged case had >50% positive tumor cells. Analysis of genome-wide copy number, mutational, and gene expression profiles revealed that CCND1-rearranged cases were similar to MCL, whereas CCND1-non-rearranged cases resembled DLBCL. Despite the SOX11 negativity by immunohistochemistry, CCND1-rearranged cases had a notable trend (P = 0.064) of higher SOX11 mRNA levels compared to non-rearranged cases. Here, we show for the first time that CCND1 rearrangement could be useful for identifying CD5/SOX11 double-negative pleomorphic MCL in cases diagnosed as cyclin D1 protein-positive DLBCL. Cases with >50% cyclin D1 protein-positive tumor cells immunohistochemically and higher SOX11 mRNA levels are more likely to have a CCND1 rearrangement, and fluorescence in situ hybridization can be used to detect the rearrangement.

Spatially-resolved transcriptomics reveal macrophage heterogeneity and prognostic significance in diffuse large B-cell lymphoma.

Macrophages are abundant immune cells in the microenvironment of diffuse large B-cell lymphoma (DLBCL). Macrophage estimation by immunohistochemistry shows varying prognostic significance across studies in DLBCL, and does not provide a comprehensive analysis of macrophage subtypes. Here, using digital spatial profiling with whole transcriptome analysis of CD68+ cells, we characterize macrophages in distinct spatial niches of reactive lymphoid tissues (RLTs) and DLBCL. We reveal transcriptomic differences between macrophages within RLTs (light zone /dark zone, germinal center/ interfollicular), and between disease states (RLTs/ DLBCL), which we then use to generate six spatially-derived macrophage signatures (MacroSigs). We proceed to interrogate these MacroSigs in macrophage and DLBCL single-cell RNA-sequencing datasets, and in gene-expression data from multiple DLBCL cohorts. We show that specific MacroSigs are associated with cell-of-origin subtypes and overall survival in DLBCL. This study provides a spatially-resolved whole-transcriptome atlas of macrophages in reactive and malignant lymphoid tissues, showing biological and clinical significance.

Neutralizing IL-16 enhances the efficacy of targeting Aurora-A therapy in colorectal cancer with high lymphocyte infiltration through restoring anti-tumor immunity.

Cancer cells can evade immune elimination by activating immunosuppressive signaling pathways in the tumor microenvironment (TME). Targeting immunosuppressive signaling pathways to promote antitumor immunity has become an attractive strategy for cancer therapy. Aurora-A is a well-known oncoprotein that plays a critical role in tumor progression, and its inhibition is considered a promising strategy for treating cancers. However, targeting Aurora-A has not yet got a breakthrough in clinical trials. Recent reports have indicated that inhibition of oncoproteins may reduce antitumor immunity, but the role of tumor-intrinsic Aurora-A in regulating antitumor immunity remains unclear. In this study, we demonstrated that in tumors with high lymphocyte infiltration (hot tumors), higher tumor-intrinsic Aurora-A expression is associated with a better prognosis in CRC patients. Mechanically, tumor-intrinsic Aurora-A promotes the cytotoxic activity of CD8+ T cells in immune hot CRC via negatively regulating interleukin-16 (IL-16), and the upregulation of IL-16 may impair the therapeutic effect of Aurora-A inhibition. Consequently, combination treatment with IL-16 neutralization improves the therapeutic response to Aurora-A inhibitors in immune hot CRC tumors. Our study provides evidence that tumor-intrinsic Aurora-A contributes to anti-tumor immunity depending on the status of lymphocyte infiltration, highlighting the importance of considering this aspect in cancer therapy targeting Aurora-A. Importantly, our results suggest that combining Aurora-A inhibitors with IL-16-neutralizing antibodies may represent a novel and effective approach for cancer therapy, particularly in tumors with high levels of lymphocyte infiltration.

Patterns of Oncogene Coexpression at Single-Cell Resolution Influence Survival in Lymphoma.

Cancers often overexpress multiple clinically relevant oncogenes, but it is not known if combinations of oncogenes in cellular subpopulations within a cancer influence clinical outcomes. Using quantitative multispectral imaging of the prognostically relevant oncogenes MYC, BCL2, and BCL6 in diffuse large B-cell lymphoma (DLBCL), we show that the percentage of cells with a unique combination MYC+BCL2+BCL6- (M+2+6-) consistently predicts survival across four independent cohorts (n = 449), an effect not observed with other combinations including M+2+6+. We show that the M+2+6- percentage can be mathematically derived from quantitative measurements of the individual oncogenes and correlates with survival in IHC (n = 316) and gene expression (n = 2,521) datasets. Comparative bulk/single-cell transcriptomic analyses of DLBCL samples and MYC/BCL2/BCL6-transformed primary B cells identify molecular features, including cyclin D2 and PI3K/AKT as candidate regulators of M+2+6- unfavorable biology. Similar analyses evaluating oncogenic combinations at single-cell resolution in other cancers may facilitate an understanding of cancer evolution and therapy resistance. SIGNIFICANCE: Using single-cell-resolved multiplexed imaging, we show that selected subpopulations of cells expressing specific combinations of oncogenes influence clinical outcomes in lymphoma. We describe a probabilistic metric for the estimation of cellular oncogenic coexpression from IHC or bulk transcriptomes, with possible implications for prognostication and therapeutic target discovery in cancer. This article is highlighted in the In This Issue feature, p. 1027.

Diagnostic clues for differentiating Merkel cell carcinoma from lymphoma in fine-needle aspiration cytology.

Nodal fine needle aspiration (FNA) is usually the first procedure in the work-up of malignancy of unknown primary. Merkel cell carcinoma (MCC) is an aggressive cutaneous cancer more common in Caucasians but rare among Asians. It is a diagnostic challenge in evaluating FNA from a metastatic MCC without the knowledge of a current or prior history of skin cancer. We report the case of a Taiwanese male with cervical and axillary masses. The diagnosis of the FNA from the axillary lymph node was lymphoproliferative lesion suspicious for lymphoma. The histopathological evaluation of nodal biopsy revealed a metastatic neuroendocrine carcinoma and the subsequent excision of the right palm tumor confirmed MCC. Retrospective review of the FNA and imprint cytology smears of the nodal biopsy showed nuclear molding, Indian filing and rare cytoplasmic pale bodies, but no lymphoglandular bodies. Cytologically metastatic MCC may mimic small round cell tumor including lymphoma, we consider these three cytological features as additional diagnostic clues for metastatic MCC. In this report, we present the cytologic and pathological features of this metastatic MCC and discuss the differential diagnosis of the cytologic mimickers.

Primary nasopharyngeal papillary adenocarcinoma: A CARE-compliant case report.

RATIONALE: Primary nasopharyngeal papillary adenocarcinoma is a rare nasopharyngeal neoplasm with a good prognosis and a low propensity for regional recurrence. To date, only few cases of primary nasopharyngeal papillary adenocarcinoma have been reported in the literature. PATIENT CONCERNS: A 24-year-old female patient presented with intermittent hemoptysis and blood tinge nasal discharge. DIAGNOSIS: An exophytic and pedunculated mass over the roof of the nasopharynx was found on nasopharyngoscope. Biopsy was done and the pathology confirmed well-differentiated primary nasopharyngeal papillary adenocarcinoma, strongly positive for CK7, and transcription termination factor 1; but negative for thyroglobulin. The final diagnosis was primary nasopharyngeal papillary adenocarcinoma, well-differentiated, pT1N0M0, stage I. INTERVENTIONS: The patient underwent excision of nasopharyngeal tumor under sinuscopic assistance. OUTCOMES: : No local recurrence or distant metastasis was noted during the 6 months of follow-up. LESSONS: We aim at highlighting the importance of a thorough differential diagnosis of nasopharyngeal tumor. Further investigation is still needed for providing evidence to standardize the treatment protocol.

The Fibronectin Expression Determines the Distinct Progressions of Malignant Gliomas via Transforming Growth Factor-Beta Pathway.

Due to the increasing incidence of malignant gliomas, particularly glioblastoma multiforme (GBM), a simple and reliable GBM diagnosis is needed to screen early the death-threaten patients. This study aimed to identify a protein that can be used to discriminate GBM from low-grade astrocytoma and elucidate further that it has a functional role during malignant glioma progressions. To identify proteins that display low or no expression in low-grade astrocytoma but elevated levels in GBM, glycoprotein fibronectin (FN) was particularly examined according to the mining of the Human Protein Atlas. Web-based open megadata minings revealed that FN was mainly mutated in the cBio Cancer Genomic Portal but dominantly overexpressed in the ONCOMINE (a cancer microarray database and integrated data-mining platform) in distinct tumor types. Furthermore, numerous different cancer patients with high FN indeed exhibited a poor prognosis in the PrognoScan mining, indicating that FN involves in tumor malignancy. To investigate further the significance of FN expression in glioma progression, tumor specimens from five malignant gliomas with recurrences that received at least two surgeries were enrolled and examined. The immunohistochemical staining showed that FN expression indeed determined the distinct progressions of malignant gliomas. Furthermore, the expression of vimentin (VIM), a mesenchymal protein that is strongly expressed in malignant cancers, was similar to the FN pattern. Moreover, the level of epithelial-mesenchymal transition (EMT) inducer transforming growth factor-beta (TGF-ß) was almost recapitulated with the FN expression. Together, this study identifies a protein FN that can be used to diagnose GBM from low-grade astrocytoma; moreover, its expression functionally determines the malignant glioma progressions via TGF-ß-induced EMT pathway.

Aberrant TTF-1 Expression in Peripheral T-Cell Lymphomas: A Diagnostic Pitfall.

BACKGROUND: Thyroid transcription factor-1 (TTF-1) is a useful marker for identifying thyroid and lung cancers in diagnostic pathology, particularly for the investigation of unknown primary cancers. However, some other tumors such as colorectal cancer might aberrantly express TTF-1, particularly with the less specific clone SPT24. Occasional diffuse large B-cell lymphoma (DLBCL) cases have been reported to be TTF-1-positive, yet there is no information on TTF-1 expression in peripheral T-cell lymphoma (PTCL). METHODS: We investigated a series of PTCL and DLBCL by immunohistochemistry for TTF-1 expression using 2 commercially available clones. RESULTS: We found that 33% (5/15) adult T-cell leukemia/lymphomas (ATLLs) and 25% (2/8) angioimmunoblastic T-cell lymphomas (AITLs) were positive by clone SPT24 and only 2ATLL cases were positive by clone 8G7G3/1. Overall TTF-1 expression rates of PTCL by SPT24 and 8G7G3/1 were 16% (7/43) and 5% (2/43), respectively. All DLBCLs were negative. CONCLUSION: Although TTF-1 is a relatively specific marker for thyroid and lung cancers, it might be expressed in some lymphomas, particularly PTCL when using clone SPT24. Pathologist should be aware of this possible diagnostic pitfall when using TTF-1 in investigating tumors of unknown origin.

Density and size of lymphoid follicles are useful clues in differentiating primary intestinal follicular lymphoma from intestinal reactive lymphoid hyperplasia.

BACKGROUND: Primary intestinal follicular lymphoma (PI-FL) is a rare and indolent lymphoma and is challenging for diagnosis with endoscopic biopsy specimens. Whole slide imaging (WSI) has been increasingly used for assisting pathologic diagnosis, but not for lymphoma yet, probably because there are usually too many immunostained sections in a single case. In this study we attempted to identify morphological clues of PI-FL in the endoscopic biopsy specimens by measuring various parameters using WSI. METHODS: We retrospectively investigated 21 PI-FL cases, and scanned the HE sections from 17 of these cases with endoscopic biopsy specimens. Sections from 17 intestinal biopsies showing reactive lymphoid hyperplasia were scanned for comparison. The density and diameter of lymphoid follicles and the shortest distance of these follicles to the surface epithelia were measured on WSI. Comparisons of the aforementioned parameters were made between the neoplastic and reactive follicles. RESULTS: The density of follicles was significantly higher in PI-FL than that of reactive hyperplasia (median 0.5 vs. 0.2/mm2; p < 0.01). Furthermore, the neoplastic follicles were significantly larger (median diameter 756.9 vs. 479.7 µm; p < 0.01). The shortest distance of follicles to the surface epithelia tended to be closer in PI-FL (104.7 vs. 177.8 µm, p = 0.056), but not statistically significant. CONCLUSIONS: In this study we found that in PI-FL the density and diameter of lymphoid follicles as measured from WSI were significantly different from that of intestinal reactive lymphoid hyperplasia. When facing the diagnostic challenge between these two entities in routine practice, pathologists might be alerted by these morphological clues and request for immunohistochemistry for differential diagnosis.

Identification of CD5/Cyclin D1 Double-negative Pleomorphic Mantle Cell Lymphoma: A Clinicopathologic, Genetic, and Gene Expression Study.

Pleomorphic mantle cell lymphoma (PMCL) can closely mimic diffuse large B-cell lymphoma (DLBCL) morphologically, and expression of CD5 and cyclin D1 is helpful for differential diagnosis. To date, no cases of CD5/cyclin D1 double-negative PMCL have been reported. Four cases of B-cell lymphoma with an immunophenotype of CD5(-) cyclin D1(-) SOX11(+) and morphologic features compatible with DLBCL were included. Two were previously identified, and the other 2 were screened from 500 cases of B-cell lymphoma. We analyzed their clinicopathologic, immunophenotypic, genetic, and gene expression features. Cases of cyclin D1-positive PMCL, cyclin D1-negative PMCL, germinal center B-cell (GCB) DLBCL, and activated B cell (ABC) DLBCL were also studied for comparison. Similar to other PMCL cases, these 4 patients were mainly elderly male individuals with an aggressive clinical course. None of these tumors had detectable translocations involving CCND1, CCND2, CCND3, CCNE1, CCNE2, MYC, BCL2, or BCL6. The genome-wide copy number profile of these 4 cases was similar to that of cyclin D1-negative PMCL. None of these tumors had high expression of cyclin D1, cyclin D2, or cyclin D3. Similar to cyclin D1-negative PMCL, these cases had higher expression of cyclin E1 and cyclin E2 compared with cyclin D1-positive PMCL. The gene expression pattern of these tumors was also similar to that of cyclin D1-negative PMCL. Here we report for the first time 4 cases of CD5/cyclin D1 double-negative PMCL. SOX11 positivity is useful to identify these rare tumors, and further genetic and gene expression analysis can be used to confirm the diagnosis.

Mycosis fungoides in Taiwan shows a relatively high frequency of large cell transformation and CD56 expression.

Mycosis fungoides (MF) is an indolent cutaneous T-cell lymphoma and may transform into large cell lymphoma in the disease course. The incidence of MF in Taiwan is lower as compared to that in the West. In this study we aimed to characterise the clinicopathological, immunohistochemical, and genetic features of transformed MF (t-MF) in Taiwan. We retrospectively collected MF cases from April 2004 to April 2015 from four medical centres in Taiwan, reviewed the clinical history and histopathology, and performed immunohistochemistry, in situ hybridisation for EBV (EBER), and fluorescence in situ hybridisation (FISH) for DUSP22/MUM1 gene translocation. Fifty-one specimens from 32 patients with MF were identified with a male to female ratio of 1.5:1 and a median age of 50.5 (range 16-82). Tumours from 11 patients (34%) underwent large cell transformation, with the median age at 61 (range 26-82). The tumour cells of t-MF expressed CD30 and MUM1 in 82% and 100% cases, respectively. CD56 was expressed in two (10%) of 21 MF cases and two (18%) of 11 t-MF cases, respectively; and all four CD56-positive cases were of a helper T-cell phenotype. All CD56 expressing MF and t-MF tumours tested for EBER were negative. FISH study showed rearranged DUSP22/IRF4 in one (9%) of 11 t-MF cases, but not in any of the 19 non-transformed MF specimens. Four patients with t-MF died of disease and six were alive with disease in a median follow-up time of 25 months (mean 44.7 months). Large cell transformation and aberrant CD56 expression were more frequent in patients with MF in Taiwan compared to those in the West. Larger case series and/or national studies are needed to clarify the significance and impact of large cell transformation on the prognosis of patients with MF.

Lymphoma in Taiwan: Review of 1347 neoplasms from a single institution according to the 2016 Revision of the World Health Organization Classification.

BACKGROUND/PURPOSE: Lymphoid neoplasms are heterogeneous and types of lymphoma vary in different geographic regions. In this study, we aimed at classifying the lymphoid neoplasms at our institution in Taiwan and to compare the relative frequency of various types of lymphoma in different countries. METHODS: We retrospectively searched the files of patients diagnosed with lymphoma at our institution from 2000 to 2015 based on the 2016 Revision of the World Health Organization classification. RESULTS: We identified 1339 patients with lymphoid neoplasms; among them, eight had two distinct types of lymphoid neoplasms. Of the 1347 neoplasms, 6.09% were Hodgkin lymphomas (HLs) and 93.31%, non-HL (NHLs). Among the 1257 NHLs, 82.66% were of B-cell lineage and 17.34% of T-cell lineage. The most common B-cell lymphoma types were diffuse large B-cell lymphoma, follicular lymphoma, and mucosa-associated lymphoid tissue lymphoma. Among T-cell neoplasms, 37% cases were of nodal origin and 63% cases arose in extranodal sites. The most common nodal and extranodal T-cell neoplasms were angioimmunoblastic T-cell lymphoma and extranodal natural killer/T-cell lymphoma, nasal type, respectively. CONCLUSION: We analyzed the largest series of lymphomas to date from Taiwan and concluded that HL was rare and T-cell neoplasms comprised around 17% of all NHLs in Taiwan. The relative frequency of the major lymphoma types is similar in East Asian countries, with only a minor difference, but the overall pattern in the East is quite different from that in the West, with the latter showing a higher frequency of HL and a lower rate of T-cell neoplasms.

Immunophenotypic and genetic characteristics of diffuse large B-cell lymphoma in Taiwan.

BACKGROUND/PURPOSE: Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma type. The immunophenotypic and genetic features of DLBCL in Taiwan have not been characterized. METHODS: In this study, we performed immunohistochemical analysis and interphase fluorescence in situ hybridization (FISH) using tissue microarray sections to investigate a cohort of unselected DLBCL cases in a single institution in Taiwan from 1990 to 2010. RESULTS: Of the 153 cases investigated, CD10, bcl-6, and MUM1 were expressed in 16.3%, 71.2%, and 71.9% cases, respectively, with 27.5% (n = 42) of cases being classified as having a germinal center B-cell (GCB) origin by the Hans algorithm. By FISH analysis, 19.6%, 4.6%, 26.1%, and 3.9% cases showed rearrangement at IGH, BCL2, BCL6, and MYC loci, respectively, including three (2.0%) cases of double-hit lymphoma. As compared with the non-GCB tumors, GCB tumors more frequently expressed CD10 (p < 0.001) and bcl-6 (p = 0.001) with less frequent expression of MUM1 (p = 0.007). Moreover, GCB tumors more frequently exhibited rearrangement at the BCL2 (p = 0.024) and MYC (p = 0.038) loci than non-GCB tumors. However, there was no survival difference between these two groups. CONCLUSION: In this first series of DLBCL evaluation from Taiwan, we found that the relative frequency of GCB tumors among DLBCL was low in most East Asian countries. There is a wide range of BCL2 rearrangement rates, higher in the West and lower in East Asia. A larger and/or national study is warranted to better understand the immunophenotypic and molecular features of DLBCL in Taiwan and their respective impact on patient survival.

17ß-Estradiol Accelerated Renal Tubule Regeneration in Male Rats After Ischemia/Reperfusion-Induced Acute Kidney Injury.

Ischemic/reperfusion injury (IRI) is the most common cause of acute kidney injury (AKI). Murine studies report that pretreatment with 17ß-estradiol protects against AKI using multiple mechanisms, but how 17ß-estradiol is involved in regenerating tubular cells is unknown. To visualize the kidney injury and repair, we used 17ß-estradiol to treat rats with postischemic acute kidney injury. AKI was induced by clamping the renal pedicle for 90 minutes 2 weeks after a unilateral nephrectomy. Rats were treated with an intravenous injection of 17ß-estradiol or vehicle immediately after reperfusion. Kidney injury was assessed by measuring biochemical and histopathological changes. Immunohistochemical staining of vimentin, proliferating cell nuclear antigen (PCNA), and E-cadherin were used to assess dedifferentiation, proliferation, and redifferentiation. Rats treated with 17ß-estradiol had less kidney injury than did vehicle-treated rats post-IRI day 1. The number of PCNA-positive (PCNA) cells was significantly higher in post-IRI kidneys on day 1 in 17ß-estradiol-treated rats. Moreover, vimentin and E-cadherin cells, which were interpreted as regeneration markers, were expressed earlier and significantly more copiously in 17ß-estradiol-treated rats. We hypothesize that 17ß-estradiol attenuates IRI-induced AKI by reducing inflammation and accelerating injured tubular cell regeneration.

Primary Intestinal Diffuse Large B-cell Lymphoma in Taiwan Showed a Relative Higher Rate of Perforation and EBV Association.

We retrospectively investigated 59 surgically resected primary intestinal diffuse large B-cell lymphomas (PI-DLBCL) including 31 males and 28 females with a median age of 66. Eleven (19%) tumors were perforated at presentation; 8 (14%) were multicentric. Ileum (n=24; 43%) and ileocecum (n=17; 30%) were most frequently involved. Twenty-one (36%) patients did not receive chemotherapy or radiotherapy including 6 with perforation and died in 0.2 to 7 months. The 1-, 2-, and 5-year overall survival rates were 68.4%, 56.5%, and 50.0%, respectively. Seven (12%) of 59 cases were positive for Epstein-Barr virus (EBV) by in situ hybridization. IGH, BCL2, BCL6, and MYC foci were rearranged in 22%, 3%, 17%, and 7% cases, respectively, with 14% exhibiting gain/amplification at the MYC locus. Perforation (P=0.009), high ECOG PS (≥2) (P=0.018), and no adjuvant chemotherapy (P<0.001) were poor prognostic factors but not immunophenotype including co-expression of bcl-2 and myc, EBV status, or chromosomal aberrations. Perforation and chemotherapy remained significant by multivariate analysis. PI-DLBCL in Taiwan carried a relatively higher rate of perforation, lower frequency of germinal center B-cell phenotype, and higher EBV association as compared with studies from other geographic areas. Furthermore, perforation was a poor prognostic factor.

EBV-associated Burkitt lymphoma in Taiwan is not age-related.

This study retrospectively investigated 54 cases of sporadic Burkitt lymphoma in Taiwan with histopathology review, immunohistochemistry, Epstein-Barr virus (EBV) in situ hybridization (EBER) and fluorescence in situ hybridization (FISH). The great majority revealed typical immunophenotype and 89% (47/53) cases expressed myc protein. EBER was positive in 20% (11/54) of cases, more frequently with nodal presentation, but not significantly associated with age (pediatric vs. adult), abdominal vs. extra-abdominal presentation or overall survival (OS). MYC and IGH were rearranged in 94% (46/49) and 85% (41/48) of cases, respectively. The concordance rate between myc expression and MYC translocation was 83% (40/48). By univariate analysis, OS was statistically associated with age, with or without chemotherapy, central nervous system (CNS) involvement, CNS prophylaxis and leukemic transformation, but not gender, nodal vs. extranodal involvement, stage, immunohistochemistry, EBER, myc expression, MYC translocation or radiotherapy. By multivariate analysis, CNS involvement at presentation and administration of chemotherapy were statistically associated with OS.

Aggressive natural killer-cell neoplasm presenting in the marrow: a report of two cases including one with gains of chromosomes 4q and 9p.

Aggressive nature killer (NK)-cell neoplasm includes aggressive NK-cell leukemia (ANKL) and extranodal NK/T-cell lymphoma (ENKTL), nasal type. ANKL is rare and is characterized by a systemic neoplastic proliferation of NK-cells, usually with a leukemic presentation. ENKTL is a predominantly extranodal lymphoma, occurring mainly in the upper aerodigestive tract. Both are aggressive neoplasms strongly associated with Epstein-Barr virus (EBV). Here we report two patients with aggressive NK-cells neoplasms localized in the bone marrow (BM) who presented as prolonged fever, anemia, and thrombocytopenia. Both were treated initially as infectious disease. Imaging studies revealed splenomegaly without any nodular lesion or lymphadenopathy. BM examination revealed extensive involvement by EBV-positive NK-cells in both cases. Staging workup including nasal examination/biopsy was negative. Both patients passed away in a month. One case showed gains of chromosomes 4q and 9p by array comparative genomic hybridization. Both tumors were diagnostically challenging due to the unusual clinical presentation and absence of leukemic change, tumor mass or lymphadenopathy. Our cases demonstrate that lymphoma should be considered in patients with fever of unknown origin and bone marrow aspiration/biopsy should be performed as early diagnosis and novel therapeutic regimens may benefit these patients.