KSHV G-protein coupled receptor vGPCR oncogenic signaling upregulation of Cyclooxygenase-2 expression mediates angiogenesis and tumorigenesis in Kaposi's sarcoma.

Kaposi's sarcoma-associated herpesvirus (KSHV) vGPCR is a constitutively active G protein-coupled receptor that subverts proliferative and inflammatory signaling pathways to induce cell transformation in Kaposi's sarcoma. Cyclooxygenase-2 (COX-2) is an inflammatory mediator that plays a key regulatory role in the activation of tumor angiogenesis. Using two different transformed mouse models and tumorigenic full KSHV genome-bearing cells, including KSHV-Bac16 based mutant system with a vGPCR deletion, we demostrate that vGPCR upregulates COX-2 expression and activity, signaling through selective MAPK cascades. We show that vGPCR expression triggers signaling pathways that upregulate COX-2 levels due to a dual effect upon both its gene promoter region and, in mature mRNA, the 3'UTR region that control mRNA stability. Both events are mediated by signaling through ERK1/2 MAPK pathway. Inhibition of COX-2 in vGPCR-transformed cells impairs vGPCR-driven angiogenesis and treatment with the COX-2-selective inhibitory drug Celecoxib produces a significant decrease in tumor growth, pointing to COX-2 activity as critical for vGPCR oncogenicity in vivo and indicating that COX-2-mediated angiogenesis could play a role in KS tumorigenesis. These results, along with the overexpression of COX-2 in KS lesions, define COX-2 as a potential target for the prevention and treatment of KSHV-oncogenesis.

Cooperation of genes in HPV16 E6/E7-dependent cervicovaginal carcinogenesis trackable by endoscopy and independent of exogenous estrogens or carcinogens.

Human papillomavirus (HPV) infection is necessary but insufficient for progression of epithelial cells from dysplasia to carcinoma-in situ (CIS) to invasive cancer. The combination of mutant cellular and viral oncogenes that regulate progression of cervical cancer (CC) remains unclear. Using combinations of HPV16 E6/E7 (E+), mutant Kras (mKras) (K+) and/or loss of Pten (P-/-), we generated autochthonous models of CC without exogenous estrogen, carcinogen or promoters. Furthermore, intravaginal instillation of adenoCre virus enabled focal activation of the oncogenes/inactivation of the tumor suppressor gene. In P+/+ mice, E6/E7 alone (P+/+E+K-) failed to cause premalignant changes, while mKras alone (P+/+E-K+) caused persistent mucosal abnormalities in about one-third of mice, but no cancers. To develop cancer, P+/+ mice needed both E6/E7 and mKras expression. Longitudinal endoscopies of P+/+E+K+ mice predicted carcinoma development by detection of mucosal lesions, found on an average of 23 weeks prior to death, unlike longitudinal quantitative PCRs of vaginal lavage samples from the same mice. Endoscopy revealed that individual mice differed widely in the time required for mucosal lesions to appear after adenoCre and in the time required for these lesions to progress to cancer. These cancers developed in the transition zone that extends, unlike in women, from the murine cervix to the distal vagina. The P-/-E+K+ genotype led to precipitous cancer development within a few weeks and E6/E7-independent cancer development occurred in the P-/-E-K+ genotype. In the P-/-E+K- genotype, mice only developed CIS. Thus, distinct combinations of viral and cellular oncogenes are involved in distinct steps in cervical carcinogenesis.

Pembrolizumab, pomalidomide, and low-dose dexamethasone for relapsed/refractory multiple myeloma.

Programmed death 1 (PD-1) receptor and its ligand (PD-L1) facilitate immune evasion in multiple myeloma (MM). We hypothesized that pembrolizumab, PD-1-antibody, can enhance antimyeloma cellular immunity generated by pomalidomide, leading to improved clinical responses. In this single-center, phase 2 study, 48 patients with relapsed/refractory MM (RRMM) received 28-day cycles of pembrolizumab, 200 mg IV every 2 weeks, pomalidomide 4 mg daily for 21 days, and dexamethasone 40 mg weekly. Patients had a median of 3 (range: 2-5) lines of therapy, median age 64 (range: 35-83) years, and had received both an immune modulatory drug (IMiD) and proteasome inhibitor: (35 [73%] of 48) were refractory to both; (31 [70%]) had received an autologous transplant, and (30 [62%]) had high-risk cytogenetics. Adverse events grade 3 to 4 occurred in (19 [40%] of 48 patients), including hematologic toxicities (19 [40%]), hyperglycemia (12 [25%]), and pneumonia (7 [15%]). Autoimmune events included pneumonitis (6 [13%]) and hypothyroidism (5 [10%]), mostly ≤ grade 2. Objective responses occurred in (29 [60%] of 48) patients, including stringent complete response/complete response (4 [8%]), very good partial response (9 [19%]), and partial response (16 [33%]); median duration of response was 14.7 months. At median follow-up of 15.6 months, progression-free survival (PFS) was 17.4 months and overall survival was not reached. Analyses of pretreatment marrow samples revealed a trend for increased expression of PD-L1 in responding patients and longer PFS with increased T-lymphocyte infiltrates, irrespective of PD-1 expression. Pembrolizumab, pomalidomide, and low-dose dexamethasone have acceptable safety and durable responses in RRMM patients. This trial was registered at www.clincialtrials.gov as #NCT02289222.

Tumor-associated fibroblasts predominantly come from local and not circulating precursors.

Fibroblasts are common cell types in cancer stroma and lay down collagen required for survival and growth of cancer cells. Although some cancer therapy strategies target tumor fibroblasts, their origin remains controversial. Multiple publications suggest circulating mesenchymal precursors as a source of tumor-associated fibroblasts. However, we show by three independent approaches that tumor fibroblasts derive primarily from local, sessile precursors. First, transplantable tumors developing in a mouse expressing green fluorescent reporter protein (EGFP) under control of the type I collagen (Col-I) promoter (COL-EGFP) had green stroma, whereas we could not find COL-EGFP(+) cells in tumors developing in the parabiotic partner lacking the fluorescent reporter. Lack of incorporation of COL-EGFP(+) cells from the circulation into tumors was confirmed in parabiotic pairs of COL-EGFP mice and transgenic mice developing autochthonous intestinal adenomas. Second, transplantable tumors developing in chimeric mice reconstituted with bone marrow cells from COL-EGFP mice very rarely showed stromal fibroblasts expressing EGFP. Finally, cancer cells injected under full-thickness COL-EGFP skin grafts transplanted in nonreporter mice developed into tumors containing green stromal cells. Using multicolor in vivo confocal microscopy, we found that Col-I-expressing fibroblasts constituted approximately one-third of the stromal mass and formed a continuous sheet wrapping the tumor vessels. In summary, tumors form their fibroblastic stroma predominantly from precursors present in the local tumor microenvironment, whereas the contribution of bone marrow-derived circulating precursors is rare.

High prevalence of MiTF staining in undifferentiated pleomorphic sarcoma: caution in the use of melanocytic markers in sarcoma.

AIMS: The diagnosis of undifferentiated pleomorphic sarcoma (UPS) may be challenging, as other lesions with undifferentiated spindle cell morphology must be excluded, including melanoma. Microphthalmia-associated transcription factor (MiTF) stains naevi and epithelioid melanomas, as well as some mesenchymal neoplasms. The aim of this study was to evaluate the prevalence of MiTF and melanocytic markers in UPS and a subset of atypical fibroxanthoma (AFX). METHODS AND RESULTS: MiTF, SOX10, Melan-A, HMB45 and S100 immunostaining was performed on resection specimens from 19 UPSs and five AFXs. Next-generation sequencing of 50 genes was performed in UPSs to exclude dedifferentiated melanoma. In 17 of 19 UPSs (89%), tumour cells showed nuclear positivity for MiTF that was not eliminated by casein block. Three showed focal nuclear staining for HMB45, which was eliminated by casein block. One showed focal nuclear vacuole staining for S100 with red but not brown chromogen. None expressed SOX10 or Melan-A. Mutational analysis of 15 UPSs with adequate DNA showed no mutations within hotspot regions of BRAF, KIT, or NRAS. Four of five AFXs (80%) stained with MiTF; other markers were negative. CONCLUSION: There is a high prevalence of nuclear MiTF expression in UPSs (89%) and AFXs (80%). Rare UPSs showed non-specific nuclear HMB45 or S100 staining. These findings argue against using MiTF in isolation to differentiate between UPS or AFX and melanoma, and caution in interpreting focal staining for a single additional melanocytic marker. Casein block may eliminate non-specific staining. MiTF should be used to support a diagnosis of melanoma only if multiple melanocytic markers are positive.

Blastic plasmacytoid dendritic cell neoplasm with leukemic presentation: 10-Color flow cytometry diagnosis and HyperCVAD therapy.

Few studies describe the comprehensive immunophenotypic pattern of blastic plasmacytoid dendritic cell neoplasm (BPDCN) in the bone marrow and its treatment. This retrospective analysis evaluates the diagnostic flow cytometry (FCM) pattern and outcome of nine patients diagnosed with BPDCN. A four-tube 10-color FCM panel used for diagnosis of acute leukemia (AL), showed cells in the blast gate (CD45dim/low SSC) and were positive for CD4(bright), CD33(dim), CD56(heterogenous), CD123(bright), CD36, CD38, HLA-DR, CD71. Seven patients received front-line induction therapy with HyperCVAD with an overall response rate of 86%. Five of six responders underwent planned allogeneic hematopoietic cell transplantation (allo-HCT). For a median follow up of 13.3 months, the 1-year disease free survival and overall survival were 56 and 67%, respectively. An accurate diagnosis of BPDCN can be made by 10-color FCM using a four-tube AL panel demonstrating a characteristic pattern of antigen expression. Front-line induction chemotherapy with HyperCVAD can yield high remission rates, but allo-HCT is required for long-term durable remissions.

Adhesion to osteopontin in the bone marrow niche regulates lymphoblastic leukemia cell dormancy.

Malignant cells may evade death from cytotoxic agents if they are in a dormant state. The host microenvironment plays important roles in cancer progression, but how niches might control cancer cell dormancy is little understood. Here we show that osteopontin (OPN), an extracellular matrix molecule secreted by osteoblasts, can function to anchor leukemic blasts in anatomic locations supporting tumor dormancy. We demonstrate that acute lymphoblastic leukemia (ALL) cells specifically adhere to OPN in vitro and secrete OPN when localized to the endosteal niche in vivo. Using intravital microscopy to perform imaging studies of the calvarial bone marrow (BM) of xenografted mice, we show that OPN is highly expressed adjacent to dormant tumor cells within the marrow. Inhibition of the OPN-signaling axis significantly increases the leukemic cell Ki-67 proliferative index and leads to a twofold increase in tumor burden in treated mice. Moreover, using cell-cycle-dependent Ara-C chemotherapy to produce minimal residual disease (MRD) in leukemic mice, we show that OPN neutralization synergizes with Ara-C to reduce detectable BM MRD. Taken together, these data suggest that ALL interacts with extracellular OPN within the malignant BM, and that this interaction induces cell cycle exit in leukemic blasts, protecting them from cytotoxic chemotherapy.

PIM1 gene cooperates with human BCL6 gene to promote the development of lymphomas.

Diffuse large B-cell lymphomas in humans are associated with chromosomal rearrangements (∼40%) and/or mutations disrupting autoregulation (∼16%) involving the BCL6 gene. Studies of lymphoma development in humans and mouse models have indicated that lymphomagenesis evolves through the accumulation of multiple genetic alterations. Based on our prior studies, which indicated that carcinogen-induced DNA mutations enhance the incidence of lymphomas in our mouse model expressing a human BCL6 transgene, we hypothesized that mutated genes are likely to play an important cooperative role in BCL6-associated lymphoma development. We used retroviral insertional mutagenesis in an effort to identify which genes cooperate with BCL6 in lymphomagenesis in our BCL6 transgenic mice. We identified PIM1 as the most frequently recurring cooperating gene in our murine BCL6-associated lymphomas (T- and B-cell types), and we observed elevated levels of PIM1 mRNA and protein expression in these neoplasms. Further, immunohistochemical staining, which was performed in 20 randomly selected BCL6-positive human B- and T-cell lymphomas, revealed concurrent expression of BCL6 and PIM1 in these neoplasms. As PIM1 encodes a serine/threonine kinase, PIM1 kinase inhibition may be a promising therapy for BCL6/PIM1-positive human lymphomas.

Trisomy 8 Defines a Distinct Subtype of Myeloproliferative Neoplasms Driven by the MYC-Alarmin Axis.

Despite advances in understanding the genetic abnormalities in myeloproliferative neoplasms (MPNs) and the development of JAK2 inhibitors, there is an urgent need to devise new treatment strategies, particularly for triple negative myelofibrosis (MF) patients who lack mutations in the JAK2 kinase pathway and have very poor clinical outcomes. Here we report that MYC copy number gain and increased MYC expression frequently occur in triple negative MF, and that MYC-directed activation of S100A9, an alarmin protein that plays pivotal roles in inflammation and innate immunity, is necessary and sufficient to drive development and progression of MF. Notably, the MYC-S100A9 circuit provokes a complex network of inflammatory signaling that involves numerous hematopoietic cell types in the bone marrow microenvironment. Accordingly, genetic ablation of S100A9 or treatment with small molecules targeting the MYC-S100A9 pathway effectively ameliorates MF phenotypes, highlighting the MYC-alarmin axis as a novel therapeutic vulnerability for this subgroup of MPNs.

Review and Updates on Systemic Mastocytosis and Related Entities.

Mast cell disorders range from benign proliferations to systemic diseases that cause anaphylaxis and other diverse symptoms to mast cell neoplasms with varied clinical outcomes. Mastocytosis is the pathologic process of the accumulation of abnormal mast cells in different organs, mostly driven by KIT mutations, and can present as cutaneous mastocytosis, systemic mastocytosis (SM), and mast cell sarcoma. The WHO 5th edition classification divides systemic mastocytosis into bone marrow mastocytosis, indolent systemic mastocytosis, smoldering systemic mastocytosis, aggressive systemic mastocytosis, systemic mastocytosis with an associated hematologic neoplasm, and mast cell leukemia. The new ICC classifies SM slightly differently. The diagnosis of SM requires the integration of bone marrow morphologic, immunophenotypic, and molecular findings, as well as clinical signs and symptoms. Moreover, understanding the wide range of clinical presentations for patients with mast cell disorders is necessary for accurate and timely diagnosis. This review provides an updated overview of mast cell disorders, with a special emphasis on SM, including the latest approaches to diagnosis, prognostic stratification, and management of this rare disease.

BAP1 cancer syndrome: malignant mesothelioma, uveal and cutaneous melanoma, and MBAITs.

BACKGROUND: BRCA1-associated protein 1 (BAP1) is a tumor suppressor gene located on chromosome 3p21. Germline BAP1 mutations have been recently associated with an increased risk of malignant mesothelioma, atypical melanocytic tumors and other neoplasms. To answer the question if different germline BAP1 mutations may predispose to a single syndrome with a wide phenotypic range or to distinct syndromes, we investigated the presence of melanocytic tumors in two unrelated families (L and W) with germline BAP1 mutations and increased risk of malignant mesothelioma. METHODS: Suspicious cutaneous lesions were clinically and pathologically characterized and compared to those present in other families carrying BAP1 mutations. We then conducted a meta-analysis of all the studies reporting BAP1-mutated families to survey cancer risk related to the germline BAP1 mutation (means were compared using t-test and proportions were compared with Pearson χ2 test or two-tailed Fisher's exact test). RESULTS: Melanocytic tumors: of the five members of the L family studied, four (80%) carried a germline BAP1 mutation (p.Gln684*) and also presented one or more atypical melanocytic tumors; of the seven members of W family studied, all carried a germline BAP1 mutation (p.Pro147fs*48) and four of them (57%) presented one or more atypical melanocytic tumors, that we propose to call "melanocytic BAP1-mutated atypical intradermal tumors" (MBAITs). Meta-analysis: 118 individuals from seven unrelated families were selected and divided into a BAP1-mutated cohort and a BAP1-non-mutated cohort. Malignant mesothelioma, uveal melanoma, cutaneous melanoma, and MBAITs prevalence was significantly higher in the BAP1-mutated cohort (p ≤ 0.001). CONCLUSIONS: Germline BAP1 mutations are associated with a novel cancer syndrome characterized by malignant mesothelioma, uveal melanoma, cutaneous melanoma and MBAITs, and possibly by other cancers. MBAITs provide physicians with a marker to identify individuals who may carry germline BAP1 mutations and thus are at high risk of developing associated cancers.

Myelodysplastic/myeloproliferative neoplasms.

The myelodysplastic/myeloproliferative neoplasms (MDS/MPN) include clonal myeloid neoplasms that overlap the MDS and MPN categories and at the time of initial diagnosis exhibit some clinical, laboratory, or morphologic features supporting the diagnosis of myelodysplastic syndrome (MDS) and at the same time show proliferative features in keeping with the diagnosis of a myeloproliferative neoplasm (MPN). Although the clinical, morphologic, and laboratory findings vary along a continuum from MDS to MPN, distinctive features are usually present that allow assignment of most of the cases to 1 of 3 distinct subtypes recognized by the 2008 World Health Organization (WHO) classification: chronic myelomonocytic leukemia (CMML), atypical chronic myeloid leukemia, BCR-ABL(-)(aCML, BCR-ABL1(-)), and juvenile myelomonocytic leukemia (JMML). The WHO classification also recognizes a provisional category of the MDS/MPN, unclassifiable (MDS/MPN, U), including the provisional entity of refractory anemia with ring sideroblasts and thrombocytosis (RARS-T). In the past 2 to 3 years since the publication of the WHO classification in 2008, dynamic progress in array technologies and next-generation amplicon deep sequencing has provided new insights into the molecular pathogenesis of MDS/MPN, especially CMML and JMML. In this review we will give an overview of these neoplasms and focus on adult MDS/MPN, especially CMML. We will give only brief updates for aCML and RARS-T; JMML will be discussed in a separate article.

Radar plots facilitate differential diagnosis of acute promyelocytic leukemia and NPM1+ acute myeloid leukemia by flow cytometry.

BACKGROUND: Acute promyelocytic leukemia (APL) is one of the most life-threatening hematological emergencies and requires a prompt correct diagnosis by cytomorphology and flow cytometry (FCM) with later confirmation by cytogenetics/molecular genetics. However, nucleophosmin 1 muted acute myeloid leukemia (NPM1+ AML) can mimic APL, especially the hypogranular variant of APL. Our study aimed to develop a novel, Radar plot-based FCM strategy to distinguish APLs and NPM1+ AMLs quickly and accurately. METHOD: Diagnostic samples from 52 APL and 32 NPM1+ AMLs patients were analyzed by a 3-tube panel of 10-color FCM. Radar plots combining all markers were constructed for each tube. Percentages of positive leukemic cells and mean fluorescence intensity were calculated for all the markers. RESULTS: APL showed significantly higher expression of CD64, CD2, and CD13, whereas more leukemic cells were positive for CD11b, CD11c, CD15, CD36, and HLA-DR in NPM1+ AMLs. Radar plots featured CD2 expression, a lack of a monocytic component, lack of expression of HLA-DR and CD15, and a lack of a prominent CD11c+ population as recurring characteristics of APL. The presence of blasts with low SSC, presence of at least some monocytes, some expression of HLA-DR and/or CD15, and a prominent CD11c population were recurrent characteristics of NPM1+ AMLs. Radar plot analysis could confidently separate all hypergranular APL cases from any NPM1+ AML and in 90% of cases between variant APL and blastic NPM1+ AML. CONCLUSION: Radar plots can potentially add to differential diagnostics as they exhibit characteristic patterns distinguishing APL and different types of NPM1+ AMLs.

PDCD2, a protein whose expression is repressed by BCL6, induces apoptosis in human cells by activation of the caspase cascade.

We have previously reported that the human programmed cell death-2 gene (PDCD2), a target of BCL6 repression, is likely to be important in the pathogenesis of certain human lymphomas. We now demonstrate that transfection of a construct expressing PDCD2 induces apoptosis in human cell lines, that this occurs, at least in part, through activation of the caspase cascade, and, furthermore, that caspase inhibitors block this effect. Immunohistochemical studies in human benign lymphoid and lymphoma tissues support these findings. In addition, transfection of a VP16-BCL6 zinc fingers fusion protein, which competes with the binding of endogenous BCL6 in a Burkitt lymphoma cell line, increases PDCD2 protein expression and apoptosis, and knockdown of the PDCD2 protein in this cell line by PDCD2-specific small interfering RNA duplexes inhibits apoptosis. These studies indicate that one function of PDCD2 is to promote apoptosis in several human and mammalian cell lines and tissues, including lymphoma. Although the pathways involved in lymphomagenesis are likely to be multiple and complex, it is plausible that repression of PDCD2 expression by BCL6, which, in turn, leads to downregulation of apoptosis, is one mechanism involved in BCL6-associated lymphomatous transformation. The usefulness of increasing PDCD2 expression in the treatment of certain lymphomas merits further investigation.

Role of defective Oct-2 and OCA-B expression in immunoglobulin production and Kaposi's sarcoma-associated herpesvirus lytic reactivation in primary effusion lymphoma.

Primary effusion lymphoma (PEL) is a distinct type of B-cell non-Hodgkin lymphoma characterized by the presence of Kaposi's sarcoma-associated herpesvirus (KSHV/human herpesvirus 8). Despite having a genotype and gene expression signature of highly differentiated B cells, PEL does not usually express surface or cytoplasmic immunoglobulin (Ig). We show the lack of Oct-2 and OCA-B transcription factors to be responsible, at least in part, for this defect in Ig production. Like Ig genes, ORF50, the key regulator of the switch from latency to lytic reactivation, contains an octamer motif within its promoter. We therefore examined the impact of Oct-2 and OCA-B on ORF50 activation. The binding of Oct-1 to the ORF50 promoter has been shown to significantly enhance ORF50 transactivation. We found that Oct-2, on the other hand, inhibited ORF50 expression and consequently lytic reactivation by competing with Oct-1 for the octamer motif in the ORF50 promoter. Our data suggest that Oct-2 downregulation in infected cells would be favorable to KSHV in allowing for efficient viral reactivation.

The Utility of MDM2 and CDK4 Immunohistochemistry and MDM2 FISH in Craniofacial Osteosarcoma.

Craniofacial osteosarcoma is rare (2-10% of all osteosarcomas). Most low grade fibroblastic osteosarcomas of the long bones are characterized by amplification of chromosome12q including MDM2 and CDK4 genes. This study aims to investigate the utility of MDM2 and CDK4 immunostains as well as MDM2 FISH in craniofacial osteosarcomas as a means of distinguishing them from benign fibro-osseous lesions. Cases of primary osteosarcoma and benign fibro-osseous lesions of the craniofacial bones were identified in the diagnostic pathology archives. MDM2 (SMP14 and/or IF2) and CDK4 (D9G3E and/or DCS-31) immunostains were performed on a representative block from each osteosarcoma and benign case. Fluorescence in situ hybridization (FISH) for MDM2 was performed on non-decalcified osteosarcomas. In osteosarcomas, the rate of expression of either MDM2 IF2, MDM2 SMP14, CDK4 DCS-31, or CDK4 D9G3E was 72.7% (8/11 cases), usually focal and weak. Using the MDM2 IF2 clone and the CDK4 DCS-31 clone, MDM2 and CDK4 were negative in lesional cells in all 14 benign fibro-osseous lesions. Using the IF2 and SMP14 clones, MDM2 nuclear expression was present in associated osteoclast-like giant cells in both benign and malignant cases. Of 4 successful cases, 1 high grade osteosarcoma was positive for MDM2 amplification. MDM2 or CDK4 expression or MDM2 amplification may aid in a diagnosis of head and neck osteosarcoma. However, when absent, sarcoma is not excluded. Due to focal weak expression of MDM2 in tumor cells in conjunction with nuclear expression in associated giant cells, caution should be exercised when interpreting positive stains.

Diffuse blastoid B-cell lymphoma: a histologically aggressive variant of t(14;18)-negative follicular lymphoma.

Among the diffuse lymphomas of B-cell origin, we have encountered one variant displaying blastoid features that morphologically mimic lymphoblastic lymphoma, the blastoid variant of mantle cell lymphoma, and the so-called blastoid transformation of follicular lymphoma. To better characterize this entity, we studied eight cases morphologically, immunohistochemically, and by fluorescence in situ hybridization (FISH) for cytogenetic abnormalities commonly associated with follicular lymphoma and B-cell lymphomas exhibiting high-grade histological features. All eight cases were presented as de novo neoplasms, and displayed an entirely diffuse (five cases) or only minimal follicular (three cases) growth pattern. The neoplastic lymphoid cells were of medium size with round nuclei, fine chromatin, inconspicuous nucleoli, and high mitotic rate; they expressed CD10, BCL6, and BCL2-a phenotype consistent with follicle center cell origin. A proportion of cases expressed MUM1. Their lack of TdT and CYCLIN D1 distinguished them from lymphoblastic lymphoma and the blastoid mantle cell lymphoma, respectively. The neoplastic lymphoid cells consistently expressed CD43 (seven of eight cases) and occasionally other T-cell-associated antigens, including CD5, CD7, CD8, and CD57. Although all cases overexpressed BCL2, t(14;18) was not detected in any of the five cases examined by FISH; instead, extra copies of chromosome 18 were found in four of five cases. Finally, other cytogenetic abnormalities, including structural abnormalities of BCL6 (allelic loss/gain, rearrangement), monosomy 7, del(13)(q14), and MYC allelic loss, were frequently detected. The combination of a B-cell CD10+ BCL6+ BCL2+ phenotype in the presence of structural abnormalities of BCL6 is consistent with a follicular center cell derivation for our cases. The lack of t(14;18) seen in our cases, although rare in most cases of follicular lymphoma, has been nevertheless reported in cases of follicular lymphoma with a predominantly diffuse growth pattern. The molecular pathogenesis, clinical manifestations, and prognostic significance of these lesions remain to be elucidated.

PAX-5 expression in pulmonary neuroendocrine neoplasms: its usefulness in surgical and fine-needle aspiration biopsy specimens.

The World Health Organization classification of lung tumors recognizes 4 histologic subtypes of pulmonary neuroendocrine carcinomas (NECs), which include typical carcinoids (TCs), atypical carcinoids (ACs), small cell carcinomas (SCCs), and large cell NECs (LCNECs). These tumors can be misclassified owing to morphologic parallels, indicating the necessity for adjunctive tests for correct classification. We evaluated immunohistochemical expression of PAX-5 in histologic and fine-needle aspiration (FNA) specimens of pulmonary NECs. Staining was stratified by intensity (0 to 3+) and percentage of cells stained as focal (<10%) or diffuse (=10%). PAX-5 expression was present in 29/37 (78%) of high-grade NECs (22/26 SCCs, 1/2 LCNECs, and 6/9 combined tumors) and none of 51 TCs and ACs; FNA specimens showed concordant staining. This study confirmed that PAX-5 is a useful marker in FNA and surgical specimens for the discrimination of low- to intermediate-grade NECs from high-grade NECs with 100% specificity and 79% sensitivity in surgical specimens.