Microenvironmental immune cell alterations across the spectrum of nodular lymphocyte predominant Hodgkin lymphoma and T-cell/histiocyte-rich large B-cell lymphoma.

Background: The clinicopathological spectrum of nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), also known as nodular lymphocyte predominant B-cell lymphoma, partially overlaps with T-cell/histiocyte-rich large B-cell lymphoma (THRLCBL). NLPHL histology may vary in architecture and B-cell/T-cell composition of the tumour microenvironment. However, the immune cell phenotypes accompanying different histological patterns remain poorly characterised. Methods: We applied a multiplexed immunofluorescence workflow to identify differential expansion/depletion of multiple microenvironmental immune cell phenotypes between cases of NLPHL showing different histological patterns (as described by Fan et al, 2003) and cases of THRLBCL. Results: FOXP3-expressing T-regulatory cells were conspicuously depleted across all NLPHL cases. As histology progressed to variant Fan patterns C and E of NLPHL and to THRLBCL, there were progressive expansions of cytotoxic granzyme-B-expressing natural killer and CD8-positive T-cells, PD1-expressing CD8-positive T-cells, and CD163-positive macrophages including a PDL1-expressing subset. These occurred in parallel to depletion of NKG2A-expressing natural killer and CD8-positive T-cells. Discussion: These findings provide new insights on the immunoregulatory mechanisms involved in NLPHL and THLRBCL pathogenesis, and are supportive of an increasingly proposed biological continuum between these two lymphomas. Additionally, the findings may help establish new biomarkers of high-risk disease, which could support a novel therapeutic program of immune checkpoint interruption targeting the PD1:PDL1 and/or NKG2A:HLA-E axes in the management of high-risk NLPHL and THRLBCL.

Response-adapted omission of radiotherapy in children and adolescents with early-stage classical Hodgkin lymphoma and an adequate response to vincristine, etoposide, prednisone, and doxorubicin (EuroNet-PHL-C1): a titration study.

BACKGROUND: Children and adolescents with early-stage classical Hodgkin lymphoma have a 5-year event-free survival of 90% or more with vincristine, etoposide, prednisone, and doxorubicin (OEPA) plus radiotherapy, but late complications of treatment affect survival and quality of life. We investigated whether radiotherapy can be omitted in patients with adequate morphological and metabolic responses to OEPA. METHODS: The EuroNet-PHL-C1 trial was designed as a titration study and recruited patients at 186 hospital sites across 16 European countries. Children and adolescents with newly diagnosed stage IA, IB, and IIA classical Hodgkin lymphoma younger than 18 years of age were assigned to treatment group 1 to be treated with two cycles of OEPA (vincristine 1·5 mg/m2 intravenously, capped at 2 mg, on days 1, 8, and 15; etoposide 125 mg/m2 intravenously, on days 1-5; prednisone 60 mg/m2 orally on days 1-15; and doxorubicin 40 mg/m2 intravenously on days 1 and 15). If no adequate response (a partial morphological remission or greater and PET negativity) had been achieved after two cycles of OEPA, involved-field radiotherapy was administered at a total dose of 19·8 Gy (usually in 11 fractions of 1·8 Gy per day). The primary endpoint was event-free survival. The primary objective was maintaining a 5-year event-free survival rate of 90% in patients with an adequate response to OEPA without radiotherapy. We performed intention-to-treat and per-protocol analyses. The trial was registered at ClinicalTrials.gov (NCT00433459) and with EUDRACT, (2006-000995-33) and is completed. FINDINGS: Between Jan 31, 2007, and Jan 30, 2013, 2131 patients were registered and 2102 patients were enrolled onto EuroNet-PHL-C1. Of these 2102 patients, 738 with early-stage disease were allocated to treatment group 1. Median follow-up was 63·3 months (IQR 60·1-69·8). We report on 714 patients assigned to and treated on treatment group 1; the intention-to-treat population comprised 713 patients with 323 (45%) male and 390 (55%) female patients. In 440 of 713 patients in the intention-to-treat group who had an adequate response and did not receive radiotherapy, 5-year event-free survival was 86·5% (95% CI 83·3-89·8), which was less than the 90% target rate. In 273 patients with an inadequate response who received radiotherapy, 5-year event-free survival was 88·6% (95% CI 84·8-92·5), for which the 95% CI included the 90% target rate. The most common grade 3-4 adverse events were neutropenia (in 597 [88%] of 680 patients) and leukopenia (437 [61%] of 712). There were no treatment-related deaths. INTERPRETATION: On the basis of all the evidence, radiotherapy could be omitted in patients with early-stage classical Hodgkin lymphoma and an adequate response to OEPA, but patients with risk factors might need more intensive treatment. FUNDING: Deutsche Krebshilfe, Elternverein für Krebs-und leukämiekranke Kinder, Gießen, Kinderkrebsstiftung Mainz of the Journal Oldtimer Markt, Tour der Hoffnung, Menschen für Kinder, Mitteldeutsche Kinderkrebsforschung, Programme Hospitalier de Recherche Clinique, and Cancer Research UK.

Response-adapted omission of radiotherapy and comparison of consolidation chemotherapy in children and adolescents with intermediate-stage and advanced-stage classical Hodgkin lymphoma (EuroNet-PHL-C1): a titration study with an open-label, embedded, multinational, non-inferiority, randomised controlled trial.

BACKGROUND: Children and adolescents with intermediate-stage and advanced-stage classical Hodgkin lymphoma achieve an event-free survival at 5 years of about 90% after treatment with vincristine, etoposide, prednisone, and doxorubicin (OEPA) followed by cyclophosphamide, vincristine, prednisone, and procarbazine (COPP) and radiotherapy, but long-term treatment effects affect survival and quality of life. We aimed to investigate whether radiotherapy can be omitted in patients with morphological and metabolic adequate response to OEPA and whether modified consolidation chemotherapy reduces gonadotoxicity. METHODS: Our study was designed as a titration study with an open-label, embedded, multinational, non-inferiority, randomised controlled trial, and was carried out at 186 hospital sites across 16 European countries. Children and adolescents with newly diagnosed intermediate-stage (treatment group 2) and advanced-stage (treatment group 3) classical Hodgkin lymphoma who were younger than 18 years and stratified according to risk using Ann Arbor disease stages IIAE, IIB, IIBE, IIIA, IIIAE, IIIB, IIIBE, and all stages IV (A, B, AE, and BE) were included in the study. Patients with early disease (treatment group 1) were excluded from this analysis. All patients were treated with two cycles of OEPA (1·5 mg/m2 vincristine taken intravenously capped at 2 mg, on days 1, 8, and 15; 125 mg/m2 etoposide taken intravenously on days 1-5; 60 mg/m2 prednisone taken orally on days 1-15; and 40 mg/m2 doxorubicin taken intravenously on days 1 and 15). Patients were randomly assigned to two (treatment group 2) or four (treatment group 3) cycles of COPP (500 mg/m2 cyclophosphamide taken intravenously on days 1 and 8; 1·5 mg/m2 vincristine taken intravenously capped at 2 mg, on days 1 and 8; 40 mg/m2 prednisone taken orally on days 1 to 15; and 100 mg/m2 procarbazine taken orally on days 1 to 15) or COPDAC, which was identical to COPP except that 250 mg/m2 dacarbazine administered intravenously on days 1 to 3 replaced procarbazine. The method of randomisation (1:1) was minimisation with stochastic component and was centrally stratified by treatment group, country, trial sites, and sex. The primary endpoint was event-free survival, defined as time from treatment start until the first of the following events: death from any cause, progression or relapse of classical Hodgkin lymphoma, or occurrence of secondary malignancy. The primary objectives were maintaining 90% event-free survival at 5 years in patients with adequate response to OEPA treated without radiotherapy and to exclude a decrease of 8% in event-free survival at 5 years in the embedded COPDAC versus COPP randomisation to show non-inferiority of COPDAC. Efficacy analyses are reported per protocol and safety in the intention-to-treat population. The trial is registered with ClinicalTrials.gov (trial number NCT00433459) and EUDRACT (trial number 2006-000995-33), and is closed to recruitment. FINDINGS: Between Jan 31, 2007, and Jan 30, 2013, 2102 patients were recruited. 737 (35%) of the 2102 recruited patients were in treatment group 1 (early-stage disease) and were not included in our analysis. 1365 (65%) of the 2102 patients were in treatment group 2 (intermediate-stage disease; n=455) and treatment group 3 (advanced-stage disease; n=910). Of these 1365, 1287 (94%) patients (435 [34%] of 1287 in treatment group 2 and 852 [66%] of 1287 in treatment group 3) were included in the titration trial per-protocol analysis. 937 (69%) of 1365 patients were randomly assigned to COPP (n=471) or COPDAC (n=466) in the embedded trial. Median follow-up was 66·5 months (IQR 62·7-71·7). Of 1287 patients in the per-protocol group, 514 (40%) had an adequate response to treatment and were not treated with radiotherapy (215 [49%] of 435 in treatment group 2 and 299 [35%] of 852 in treatment group 3). 773 (60%) of 1287 patients with inadequate response were scheduled for radiotherapy (220 [51%] of 435 in the treatment group 2 and 553 [65%] of 852 in treatment group 3. In patients who responded adequately, event-free survival rates at 5 years were 90·1% (95% CI 87·5-92·7). event-free survival rates at 5 years in 892 patients who were randomly assigned to treatment and analysed per protocol were 89·9% (95% CI 87·1-92·8) for COPP (n=444) versus 86·1% (82·9-89·4) for COPDAC (n=448). The COPDAC minus COPP difference in event-free survival at 5 years was -3·7% (-8·0 to 0·6). The most common grade 3-4 adverse events (intention-to-treat population) were decreased haemoglobin (205 [15%] of 1365 patients during OEPA vs 37 [7%] of 528 treated with COPP vs 20 [2%] of 819 treated with COPDAC), decreased white blood cells (815 [60%] vs 231 [44%] vs 84 [10%]), and decreased neutrophils (1160 [85%] vs 223 [42%] vs 174 [21%]). One patient in treatment group 2 died of sepsis after the first cycle of OEPA; no other treatment-related deaths occurred. INTERPRETATION: Our results show that radiotherapy can be omitted in patients who adequately respond to treatment, when consolidated with COPP or COPDAC. COPDAC might be less effective, but is substantially less gonadotoxic than COPP. A high proportion of patients could therefore be spared radiotherapy, eventually reducing the late effects of treatment. With more refined criteria for response assessment, the number of patients who receive radiotherapy will be further decreased. FUNDING: Deutsche Krebshilfe, Elternverein für Krebs-und leukämiekranke Kinder Gießen, Kinderkrebsstiftung Mainz, Tour der Hoffnung, Menschen für Kinder, Programme Hospitalier de Recherche Clinique, and Cancer Research UK.

Peripheral nerve neurolymphomatosis: Clinical features, treatment, and outcomes.

This series characterises nine patients with neurohistopathologically proven peripheral nerve neurolymphomatosis. A search of the hospital neuropathology database from 2002 to 2019 identified biopsy proven cases. Clinical data, investigation modalities, treatments, and outcomes were collated. Median age at neuropathy onset was 47 y, the neuropathy commonly as the initial lymphoma disease manifestation. Most (8/9) presented with painful asymmetrical sensory disturbance, with additional cranial nerve involvement in three. Neurophysiology typically demonstrated multiple axonal mononeuropathies. Cerebrospinal fluid protein was often raised (6/8). Magnetic resonance imaging suggested peripheral nerve infiltration in 6/9 and positron emission tomography CT in 4/9. Bone marrow biopsy was abnormal in 6/8. Treatment involved systemic or intrathecal chemotherapy and radiotherapy. Median survival was 23 mo. Neurolymphomatosis is a rare but important cause of neuropathy, particularly in those lacking systemic evidence of lymphoma as correct aggressive treatment can prolong survival. Nerve biopsy is essential to classify lymphoma type and rule out alternatives.

Advanced stage nodular lymphocyte predominant Hodgkin lymphoma in children and adolescents: clinical characteristics and treatment outcome - a report from the SFCE & CCLG groups.

Advanced stage nodular lymphocyte predominant Hodgkin lymphoma (nLPHL) is extremely rare in children and as a consequence, optimal treatment for this group of patients has not been established. Here we retrospectively evaluated the treatments and treatment outcomes of 41 of our patients from the UK and France with advanced stage nLPHL. Most patients received chemotherapy, some with the addition of the anti CD20 antibody rituximab or radiotherapy. Chemotherapy regimens were diverse and followed either classical Hodgkin lymphoma or B non-Hodgkin lymphoma protocols. All 41 patients achieved a complete remission with first line treatment and 40 patients are alive and well in remission. Eight patients subsequently relapsed and 1 patient died of secondary cancer (9 progression-free survival events). The median time to progression for those who progressed was 21 months (5·9-73·8). The median time since last diagnosis is 87·3 months (8·44-179·20). Thirty-six (90%), 30 (75%) and 27 (68%) patients have been in remission for more than 12, 24 and 36 months, respectively. Overall, the use of rituximab combined with multi-agent chemotherapy as first line treatment seems to be a reasonable therapeutic option.

Relapsed or poorly responsive nodular lymphocyte predominant Hodgkin lymphoma in children and adolescents - a report from the United Kingdom's Children's Cancer and Leukaemia Study Group.

There is a paucity of data on the treatment outcome in children with relapsed or poorly responsive nodular lymphocyte predominant Hodgkin lymphoma (nLPHL). This retrospective report evaluates the treatment outcome in a national cohort of children with relapsed or poorly responsive nLPHL. A total of 37 patients, 22 with relapsed and 15 with poorly responding disease, are the subjects of this report. Of the 22 patients with relapsed nLPHL, 11 had relapsed after primary excision biopsy, 10 after chemotherapy and 1 after chemotherapy and involved field radiotherapy. The majority had localized disease at relapse. The median time to relapse was 8 months after chemotherapy and 11 months after excision biopsy. Seven of the 15 patients with poorly responding nLPHL had variant histology. Three patients with initial poor response did not receive any further treatment and have had no disease progression. Transformation to diffuse large B cell lymphoma, in addition to evolution from typical to variant nLPHL occurred in one patient each. Thirty-four patients have been successfully re-treated with second chemotherapy or radiotherapy. Multiple relapses were uncommon but treatable. Relapse or poorly responsive nLPHL is fully salvageable with either additional chemotherapy and or radiotherapy.

Childhood and Adolescent nodular lymphocyte predominant Hodgkin lymphoma - A review of clinical outcome based on the histological variants.

Nodular lymphocyte predominant Hodgkin lymphoma (nLPHL) comprises approximately 10-12% of all childhood Hodgkin lymphoma. As the majority have low stage disease recent years have seen a de-escalation of treatment intensity to avoid treatment-related morbidity. This report evaluates treatment outcome in children with histopathological variants of nLPHL after therapy de-escalation. Biopsies from 60 patients were reviewed and histology categorized as typical (n = 47; 78%) or variant nLPHL (n = 13; 22%). Furthermore, presence of immunoglobulin D (IgD) expression by the lymphocyte predominant (LP) cells was assessed in 41 patients. Treatment outcomes were compared according to treatment received and histopathology of nLPHL. Compared to typical nLPHL, children with variant nLPHL had higher stage disease at diagnosis (stage III: 3/13; 23% vs. 3/47; 6%, P = 0·11), lower complete response rates (6/13; 46% vs. 38/47; 81%, P = 0·029) and higher relapse rates (2/13; 15% vs. 2/47; 4%, P = 0·20). Additionally, IgD expression by LP cells was associated with poorer treatment response and was more commonly seen in patients with variant nLPHL. (11/13; 85% vs. 15/28; 54%, P = 0·08). Variant histology appears to be indicative of a poorer prognosis in patients with early stage disease, and may be an important factor to take into account when moving towards reduced intensity treatment for nLPHL.

Chronic lymphocytic leukaemia--the role of the microenvironment pathogenesis and therapy.

Chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL) is one of the more common forms of B cell malignancy. Although the condition has a variable clinical course, the trend is towards eventual relapse and the disease is considered incurable. Whilst the majority of the circulating CD5-positive neoplastic B cells are arrested in the G0 phase of the cell cycle, those in the bone marrow and lymphoid tissues proliferate at a rate of 0·1-1% of the entire clone per day. This proliferation is supported by the tissue microenvironment, which has been shown to induce upregulation of anti-apoptotic proteins and enhance the survival of the neoplastic cells. Microenvironmental factors are also thought to be important in tumour relapse and resistance to therapy. This review outlines the main signalling pathways involved in these tumour cell-stromal interactions, and includes potential therapeutic strategies based on the manipulation of key components within the CLL microenvironment.

Another look at follicular lymphoma: immunophenotypic and molecular analyses identify distinct follicular lymphoma subgroups.

AIMS: The aim of this study was to analyse the immunophenotypic and molecular features of a large series of follicular lymphomas, focusing in particular on atypical cases that fail to express CD10 and/or bcl-2. Such cases present diagnostic pitfalls, especially with regard to the differential diagnosis from follicular hyperplasia and marginal zone B-cell lymphoma. Therefore, we also included an immunohistochemical evaluation of stathmin, which is strongly expressed by germinal centre B cells, as a putative new marker for follicular lymphomas, particularly those with an atypical phenotype. METHODS AND RESULTS: Two hundred and five follicular lymphomas were investigated with immunohistochemistry and fluorescence in-situ hybridization (FISH). The use of three distinct anti-bcl-2 antibodies together with CD10 expression data and FISH analysis for bcl-2 and bcl-6 rearrangements allowed subclassification of follicular lymphoma into four distinct subgroups: (i) CD10-positive/bcl-2-positive, (ii) CD10-positive/bcl-2-negative, (iii) CD10-negative/bcl-2-positive, and (iv) CD10-negative/bcl-2-negative. All cases were bcl-6-positive. STMN1 (stathmin) was shown to be helpful in diagnosing bcl-2-negative and/or CD10-negative follicular lymphomas, and in their distinction from marginal zone B-cell lymphoma. CONCLUSIONS: Combined immunohistological and molecular analyses reveal that follicular lymphomas showing an atypical immunophenotypic and molecular profile exist, and we demonstrate that STMN1 represents a novel useful diagnostic marker for these.

30 years of lymph node pathology: biomarkers and other advances.

Over the last 30 years there has been a massive change in both the clinical and pathologic aspects of malignant lymphomas. Pathologists are now able to evaluate cellular phenotypes and lineages of tumor cells using a wide variety of biomarkers and molecular techniques. The ability to identify tumor cell phenotypes has revolutionized the classification of lymphomas, leading to an internationally agreed system based on the reliable recognition of specific clinico-pathologic entities. The World Health Organization classification combines clinical features, histomorphology, immunohistochemistry, and molecular and genetic marker data to precisely categorize lymphomas. On the clinical front the increasing use of needle core biopsies has made it easier and quicker to obtain tissue samples, and the development of (18)F-fluorodeoxyglucose positron emission tomography has revolutionized the assessment of patients both at presentation and after treatment. To improve overall outcomes for lymphoma patients there have been advances in the UK organization of cancer services. Cancer networks have been established, often with network multidisciplinary team meetings, and new diagnoses of lymphoma are reviewed on a network basis by pathologists specializing in the field. National and supranational quality control systems are in place for immunohistochemistry and for molecular techniques and multicenter clinical trials provide information about the efficacy of treatment regimens. The outcome of these advances is that a patient presenting in 2012 with suspected lymphoma can expect to be biopsied rapidly, to receive an accurate pathologic diagnosis by an expert hematopathologist, which will include prognostic marker information, and to have comprehensive disease assessment and discussion by a multidisciplinary team before embarking on the most appropriate treatment for his or her clinical situation.

Primary follicular lymphoma of the testis in children and adolescents.

This study reports 6 cases of primary follicular lymphoma of the testis (PFLT) in children and adolescents correlated with clinical presentation, pathologic features, treatment, and outcome. All 6 patients (age, 3 to 16 y; median, 4 y) had PFLT grade 3 with disease limited to the testis, completely resected and treated with 2 courses of chemotherapy (cyclophosphamide, vincristine, prednisone, doxorubicin). Event-free survival was 100% (follow-up: median, 73 mo; mean, 53 mo; range, 6 to 96 mo). In conclusion, clinical outcome in children and adolescents with PFLT is excellent with treatment including complete surgical resection and 2 courses of cyclophosphamide, vincristine, prednisone, doxorubicin.

Variable antigen expression in hepatoblastomas.

Hepatoblastoma is a malignant tumor that typically presents as a mass in the liver of a child less than 5 years of age. The diagnosis is usually established by means of a needle core biopsy before the treatment is commenced. The pathologic diagnosis of hepatoblastoma relies on the microscopic identification of typical morphologic features, but these may not be present in a needle core biopsy, and in this setting immunohistochemical staining has an important role in the exclusion of other childhood malignancies. We have studied 12 needle core biopsies from cases of hepatoblastoma, all of which had the diagnosis confirmed by subsequent resection of the tumor, to determine if these tumors show a diagnostic phenotype. The needle biopsies were immunostained with a standard panel of antibodies normally used in the characterization of childhood small round blue cell tumors, with the addition of antibodies directed against alpha-fetoprotein and alpha-1-antitrypsin. Our results indicate that the majority of hepatoblastomas expressed cytokeratins (10/12) and that alpha-1-antitrypsin and alpha-fetoprotein staining were positive in approximately half the cases (5/12 and 7/12, respectively). We also observed frequent expression of antigens normally expressed on other childhood tumors. A significant number of hepatoblastomas (8/12) expressed MIC-2 (CD99) an antigen normally associated with primitive neuroectodermal tumor, 4 cases showed positive staining with the neural-associated antigen NCAM (CD56), and 3 were positive with the neuroblastoma marker NB84. Occasional cases showed expression of the muscle marker desmin (2/12) and 2 cases stained with BCL2. Vimentin expression was seen in 1 case, and a single case also expressed the neural markers PGP9.5 and neurone-specific enolase. In all cases, the tumor cells were negative with CD45, WT1, and S-100. These findings indicate that the primitive cells in hepatoblastoma have a variable immunophenotype and can express antigens normally seen in other childhood malignancies. In the clinical setting of the differential diagnosis of childhood abdominal mass, hepatoblastoma shows no distinct immunohistochemical profile, and the diagnosis requires a combination of the clinical, imaging, and pathologic findings.

Long-term outcome of intractable ulcerating enterocolitis of infancy.

BACKGROUND: Chronic enterocolitis is rare in infancy and accounts for less than 0.5% of all newly diagnosed inflammatory bowel disease (IBD) in the UK. Presentation at this young age is usually indicative of underlying immunodeficiency/immunodysregulation. A group of such infants suffer intractable ulcerating enterocolitis of infancy (IE) in which there is a pan-enteritis with marked oro-anal involvement and deep flask like mucosal ulcers throughout the colon. METHODS: Retrospective review of presenting features, treatment and long-term outcome in a series of 8 children with typical IE. RESULTS: The 8 children were aged between 1 and 4 weeks at onset (median 2 weeks, mean 2.3 weeks), of which 7 were followed up for 2-22 years (median 7.5 years, mean 11 years). All 8 children had an intractable disease course requiring a colectomy for control of symptoms. The median age at colectomy was 1.7 years (range 4 months-4 years). Three children developed a generalised lymphadenopathy due to uncontrolled EBV-related lymphoid proliferations (ages 4, 12, 18). These comprised a monomorphous B-lymphoycte lympho-proliferative disorder, a large pleomorphic follicular lymphoma, and a high grade pleomorphic B cell non-Hodgkin's lymphoma. CONCLUSIONS: Infants with IE have a high risk of developing lymphomatous proliferations that appears to be related to the underlying immunodysregulation. Use of aggressive immunosuppression and acquisition of EBV infection appears to accelerate this process; hence we advocate early colectomy in confirmed cases. In children with IE screening for EBV and vigilance for abnormal lymphoid proliferations is paramount.

Ectopic thymus presenting as a subglottic mass: diagnostic and management dilemmas.

The commonest subglottic mass in infants is a congenital haemangioma, which is usually managed conservatively without a histological diagnosis. Ectopic cervical thymus is rare and usually presents as a cervical mass, with only one case of subglottic ectopic thymus reported to date. Due to its rarity, the diagnosis in most cases relies on surgical excision and histological examination. However, histological diagnosis may not always be easily reached, as is demonstrated in this case report. In this article, an infant with congenital stridor secondary to a subglottic mass is described and the clinical and diagnostic difficulties in its management are discussed.

Immunohistochemical findings in embryonal small round cell tumors with molecular diagnostic confirmation.

The diagnosis of pediatric tumors relies heavily on immunohistochemical staining of small tissue biopsies, since many entities share a "small blue cell" phenotype. More recently, molecular genetic analysis for detection of specific gene fusion products has become available. With the increased use of such molecular techniques, the authors have noted that tumors with proven molecular diagnoses can exhibit unusual patterns of immunohistochemical staining. This study examines pediatric tumors with a "small blue cell" phenotype in which molecular diagnoses were available where applicable. A panel of immunohistochemical stains was performed (S100, CD56, NB84, CD99 [MIC2], Bcl-2, CD117, CD34, desmin, MNF116, and WT1). In the 370 sections from 37 cases, all primitive neuroectodermal tumors, with and without the presence of t(11;22), demonstrated uniform membranous membrane staining with CD99 (MIC2) and focal staining with CD56, NB84, MNF116, and WT1. All rhabdomyosarcomas, both alveolar and embryonal, demonstrated uniform desmin, CD56, and cytoplasmic WT1 immunostaining. Desmoplastic small round cell tumors showed positive cytokeratin staining, with half having "dot-like" cytoplasmic desmin and WT1 positivity; some showed focal positivity for NB84, CD99, and Bcl-2. The "undifferentiated" sarcomas showed the widest range of staining, with no marker staining all cases. Neuroblastomas exhibited uniform strong staining for CD56 and NB84 and marked cytoplasmic Bcl-2 positivity, and some cases showed cytoplasmic WT1 expression. Blastematous Wilms' tumors showed uniform strong membranous staining for CD56, uniform cytoplasmic staining for Bcl-2, and nuclear expression of WT1. Embryonal pediatric malignancies can demonstrate apparently nonspecific expression patterns for several antigens, which may reflect developmental immaturity rather than specific differentiation pathways.

Posttransplant lymphoproliferative disorder presenting as CD30+, ALK+, anaplastic large cell lymphoma in a child.

We report a 15-year-old cardiac transplant recipient who developed a monomorphic posttransplant lymphoproliferative disorder (PTLPD) which demonstrated morphological and immunohistochemical features of anaplastic large cell lymphoma including CD30 and anaplastic lymphoma kinase (ALK) immunopositivity but lacking the commonly associated t(2;5) translocation. The neoplastic cells were Epstein-Barr Virus (EBV)-negative. T-cell PTLPD is an uncommon but recognized late complication in solid organ transplant recipients. This is the first reported case, to our knowledge, of PTLPD occurring in childhood with an ALK+, CD30+ anaplastic large cell lymphoma phenotype.

Reactive lymph nodes in pediatric practice.

A variety of unusual reactive conditions may be seen in lymph nodes from the pediatric age group. Some of these, such as the autoimmune lymphoproliferative syndrome, reflect underlying abnormalities of the immune system and cellular control processes, while others are related to viral infections or are of unknown cause. Many of these conditions can mimic malignant neoplasms, so it is important that pathologists recognize these unusual reactive patterns.