Soluble CD89 is a critical factor for mesangial proliferation in childhood IgA nephropathy.

Childhood IgA nephropathy (IgAN) includes a wide spectrum of clinical presentations, from isolated hematuria to acute nephritis with rapid loss of kidney function. In adults, IgAN is an autoimmune disease and its pathogenesis involves galactose deficient (Gd) IgA1, IgG anti-Gd-IgA1 autoantibodies and the soluble IgA Fc receptor (CD89). However, implication of such factors, notably soluble CD89, in childhood IgAN pathogenesis remains unclear. Here, we studied these biomarkers in a cohort of 67 patients with childhood IgAN and 42 pediatric controls. While Gd-IgA1 was only moderately increased in patient plasma, levels of circulating IgA complexes (soluble CD89-IgA and IgG-IgA) and free soluble CD89 were markedly increased in childhood IgAN. Soluble CD89-IgA1 complexes and free soluble CD89 correlated with proteinuria, as well as histological markers of disease activity: mesangial, endocapillary hypercellularity and cellular crescents. Soluble CD89 was found in patient's urine but not in urine from pediatric controls. Mesangial deposits of soluble CD89 were detected in biopsies from patients with childhood IgAN. Serum chromatographic fractions containing covalently linked soluble CD89-IgA1 complexes or free soluble CD89 from patients induced mesangial cell proliferation in vitro in a soluble CD89-dependent manner. Recombinant soluble CD89 induced mesangial cell proliferation in vitro which was inhibited by free soluble recombinant CD71 (also a mesangial IgA receptor) or mTOR blockers. Interestingly, injection of recombinant soluble CD89 induced marked glomerular proliferation and proteinuria in mice expressing human IgA1. Thus, free and IgA1-complexed soluble CD89 are key players in mesangial proliferation. Hence, our findings suggest that soluble CD89 plays an essential role in childhood IgAN pathogenesis making it a potential biomarker and therapeutic target.

SRY-negative 46,XX testicular/ovotesticular DSD: Long-term outcomes and early blockade of gonadotropic axis.

OBJECTIVE: SRY-negative 46,XX testicular and ovotesticular disorders/differences of sex development (T/OTDSD) represent a very rare and unique DSD condition where testicular tissue develops in the absence of a Y chromosome. To date, very few studies have described the phenotype, clinical and surgical management and long-term outcomes of these patients. Particularly, early blockade of the gonadotropic axis in patients raised in the female gender to minimize postnatal androgenization has never been reported. DESIGN: Retrospective description of sixteen 46,XX T/OTDSD patients. RESULTS: Sixteen 46,XX SRY-negative T/OTDSD were included. Most (12/16) were diagnosed in the neonatal period. Sex of rearing was male for six patients and female for ten, while the clinical presentation varied, with an external masculinization score from 1 to 10. Five patients raised as girl were successfully treated with GnRH analog to avoid virilization during minipuberty. Ovotestes/testes were found bilaterally for 54% of the patients and unilaterally for the others (with a contralateral ovary). Gonadal surgery preserved appropriate tissue in the majority of cases. Spontaneous puberty occurred in two girls and one boy, while two boys required hormonal induction of puberty. One of the girls conceived spontaneously and had an uneventful pregnancy. DNA analyses (SNP-array, next-generation sequencing and whole-exome sequencing) were performed. A heterozygous frameshit mutation in the NR2F2 gene was identified in one patient. CONCLUSIONS: This study presents a population of patients with 46,XX SRY-negative T/OTDSD. Early blockade of gonadotropic axis appears efficient to reduce and avoid further androgenization in patients raised as girls.

Clinical and histological differences between adults and children in new onset IgA nephropathy.

BACKGROUND: Previous reports suggest initial presentation of IgA nephropathy (IgAN) in children is different from adults. No systematic comparison of clinical, biological, and histological childhood- and adult-onset IgAN is currently available. METHODS: We compared pediatric and adult clinical and histological characteristics at IgAN diagnosis. Data on 211 consecutive patients from two different centers in Paris (82 children, 129 adults) were reviewed. Kidney biopsies were scored for Oxford classification and podocytopathic (P1) features. RESULTS: We report higher eGFR at diagnosis in children compared to adults (89.5 vs. 64 ml/min/1.73 m2; p = 0.0001) but no difference in proteinuria. Histological analysis of kidney biopsy found higher proportions of mesangial (M1) and endocapillary (E1) hypercellularity in children compared with adults (M1 [80.7% vs. 27.9%, p = 0.0001]; E1 [71.3% vs. 30%, p = 0.0001]). Focal glomerulosclerosis (S1), tubular atrophy/interstitial fibrosis ≥ 25% (T1), and P1 were more frequent in adults (S1 [81.5% vs. 61.3%, p = 0.0012], T1 [49.5% vs. 1.35%, p = 0.0001], P1 [33.8% vs. 16.4%, p = 0.008). Proteinuria associated with M1, E1, and C1 in children (M1, p = 0.0001; E1, p = 0.0005; C1, p = 0.0014) but S1, P1, and T1 in adults (S1, p = 0.0001; P1, p = 0.0001; T1, p = 0.001). After steroid treatment (41 children and 28 adults), proteinuria decreased in children (p < 0.001, follow-up 38 months) and adults (p < 0.001, follow-up 76.9 months), whereas eGFR remained stable in adults but increased significantly in children (90.6 to 110 ml/min/1.73m2). CONCLUSION: Proteinuria in children with IgAN is a marker of glomerular proliferative lesions whereas its presence in adults often reflects the presence of chronic lesions. This suggests the need for histological assessment.

Histological prognostic factors in children with Henoch-Schönlein purpura nephritis.

BACKGROUND: The management of IgA vasculitis with nephritis (IgAVN) remains controversial because of the difficulty to identify prognostic factors. This study reports the prognosis of children with IgAVN in relation to histological parameters. METHODS: All children with IgAVN diagnosed between 2000 and 2015 in three pediatric nephrology centers were included. The following histological parameters were analyzed: mesangial proliferation (MP), endocapillary proliferation (EP), crescents, active, or chronic tubular and interstitial lesions (TIa lesions/TIc lesions), and segmental glomerulosclerosis (GS). Clinical and biological data were collected at the time of renal biopsy. The primary endpoint was IgAVN remission defined as a proteinuria < 200 mg/l without renal failure. RESULTS: One hundred fifty-nine children were included with a median age of 7.6 years. Acute glomerular or TI lesions including MP, EP, crescents, and TIa lesions were observed, respectively, in 81%, 86%, 49%, and 21% of patients. Chronic glomerular lesions including GS and TIc lesions were observed in 6 and 7% of patients. Median initial proteinuria was 330 mg/mmol, albuminemia 32 g/l, and eGFR 110 ml/min/1.73 m2. One hundred twelve (70%) patients were in remission at the end of a median follow-up of 37.4 months. Chronic lesions were significantly associated with the absence of remission in multivariate analysis, whereas EP, crescents and TIa were not associated with a poor prognosis. CONCLUSIONS: Of children with IgAVN, 30% present a persistent renal disease at the end of a 3-year follow-up. Chronic histological lesions, but not EP or crescents, are associated with a bad prognosis and must be evaluated in IgAVN histological classification.

Remission of proteinuria in multidrug-resistant idiopathic nephrotic syndrome following immunoglobulin immunoadsorption.

AIM: Complete or partial resistance to prednisone and calcineurin inhibitors in children with idiopathic nephrotic syndrome often leads to end-stage renal disease. The aim of the study was to report the outcome of patients with multidrug-resistant nephrotic syndrome treated with an association of immunoglobulin immunoadsorption, intravenous immunoglobulins and B-cell depletion. METHODS: At treatment initiation, patients received ten sessions of immunoglobulin immunoadsorption and intravenous immunoglobulins in two weeks followed by one rituximab in case of remission. RESULTS: A remission of proteinuria was obtained in nine out of 14 patients at the end of the initial phase and in two additional patients after an extended period. The remission was stable in three patients and after additional IgIA and heavy immunosuppression in six. Two patients that initially responded relapsed after IgIA withdrawal and remained with an uncontrolled disease at last follow-up. Three patients did not respond to the treatment including two who were found to have a genetic podocytopathy. CONCLUSION: Patients with multidrug-resistant idiopathic nephrotic syndrome can be successfully led into remission by IgIA prior to reaching end-stage renal disease. However, IgIA does not suppress the need for heavy additional immunosuppression to control INS in most cases.

[Pulmonary glial heterotopia: Unique lesion in an infant with anencephalic twin]. / Hétérotopie gliale pulmonaire : une lésion exceptionnelle chez un nourrisson avec un jumeau anencéphale.

Pulmonary glial heterotopia is an extremely rare entity whose pathophysiology remains unclear. We report for the first time one case of pulmonary glial heterotopia occured in a one-month baby free from any malformation. She has the particularity of being born from monozygotic monochorionic twin pregnancy where her anencephalic exencephalic sister suffered a medical termination of pregnancy. She presented neonatal respiratory distress, which recurred one month later. Chest X-ray revealed bilateral cystic pulmonary lesions mainly located in the right lung. Given the suspicion of congenital cystic adenomatoid malformation (CCAM), she underwent an upper and a lower right lung lobectomy at four months old. The pathological study found a multi-cystic lesion consisted of well-differentiated and poorly cellular glial tissue sometimes lined by bronchic epithelium. There was no pathological evidence for a CCAM. The evolution was favorable after surgery with an infant who was well five months later. This is one of the very few cases where the disease did not lead to rapid death in utero or during the perinatal period. This suggests that effective management by surgery could be a decisive factor in the survival of these patients.

Renal parenchyma impairment characterization in partial unilateral ureteral obstruction in mice with intravoxel incoherent motion-MRI.

Ureteropelvic junction obstruction constitutes a major cause of progressive pediatric renal disease. The biological mechanisms underlying the renal response to obstruction can be investigated using a clinically relevant mouse model of partial unilateral ureteral obstruction (pUUO). Renal function and kidney morphology data can be evaluated using renal ultrasound, scintigraphy and uro-magnetic resonance imaging (uro-MRI), but these methods are poorly linked to histological change and not all are quantitative. Here, we propose to investigate pUUO for the first time using an intravoxel incoherent motion diffusion sequence. The aim of this study was to quantitatively characterize impairment of the kidney parenchyma in the pUUO model. This quantitative MRI method was able to assess the perfusion and microstructure of the kidney without requiring the injection of a contrast agent. The results suggest that a perfusion fraction (f) reduction is associated with a decrease in the volume of the renal parenchyma, which could be related to decreased renal vascularization. The latter may occur before impairment by fibrosis and the findings are in accordance with the literature using the UUO mice model and, more specifically, on pUUO. Further investigation is required before this technique can be made available for the diagnosis and management of children with antenatal hydronephrosis and to select the optimal timing of surgery if required.

[Results of the Massive Open Online Course (MOOC) on cancer diagnosis and evaluation of its impact on the perception of the pathology specialty]. / Massive open online course (MOOC) sur le diagnostic des cancers : bilan et évaluation de l'impact sur la perception de l'anatomie et cytologie pathologiques.

The Massive Open Online Course (or MOOC) "Diagnostic Strategies Cancers", was hosted in autumn 2016 on the platform "France Université Numérique" and had two levels of learners: students in the field of health and biology and the general public. Of the 5285 learners in 81 different countries, 1237 (23%) were successfully certified. This MOOC was also integrated into the teaching program of medical students of Paris Diderot University and Paris 13 University. Using anonymous questionnaires before and after MOOC, it has been shown that pathology is less known than other medical specialties. Participation in this MOOC led to a marked improvement in participants' knowledge of the place and role of the pathologist in the diagnosis of cancers. Regarding the students who have followed the MOOC as part of their university course, their comments were very positive, but it is necessary to make substantial adjustments in the amounts and contents of the campus-based courses.

Oncologic Phenotype of Peripheral Neuroblastic Tumors Associated With PHOX2B Non-Polyalanine Repeat Expansion Mutations.

BACKGROUND: Germline non-polyalanine repeat expansion mutations in PHOX2B (PHOX2B NPARM) predispose to peripheral neuroblastic tumors (PNT), frequently in association with other neurocristopathies: Hirschsprung disease (HSCR) or congenital central hypoventilation syndrome (CCHS). Although PHOX2B polyalanine repeat expansions predispose to a low incidence of benign PNTs, the oncologic phenotype associated with PHOX2B NPARM is still not known in detail. METHODS: We analyzed prognostic factors, treatment toxicity, and outcome of patients with PNT and PHOX2B NPARM. RESULTS: Thirteen patients were identified, six of whom also had CCHS and/or HSCR, one also had late-onset hypoventilation with hypothalamic dysfunction (LO-CHS/HD), and six had no other neurocristopathy. Four tumours were "poorly differentiated," and nine were differentiated, including five ganglioneuromas, three ganglioneuroblastomas, and one differentiating neuroblastoma, hence illustrating that PHOX2B NPARM are predominantly associated with differentiating tumors. Nevertheless, three patients had stage 4 and one patient had stage 3 disease. Segmental chromosomal alterations, correlating with poor prognosis, were found in all the six tumors analyzed by array-comparative genomic hybridization. One patient died of tumor progression, one is on palliative care, one died of hypoventilation, and 10 patients are still alive, with median follow-up of 5 years. CONCLUSIONS: Based on histological phenotype, our series suggests that heterozygous PHOX2B NPARM do not fully preclude ganglion cell differentiation in tumors. However, this tumor predisposition syndrome may also be associated with poorly differentiated tumors with unfavorable genomic profiles and clinically aggressive behaviors. The intrafamilial variability and the unpredictable tumor prognosis should be considered in genetic counseling.

CCR1 inhibition ameliorates the progression of lupus nephritis in NZB/W mice.

Systemic lupus erythematosus is a chronic inflammatory autoimmune disease, the development of which is characterized by a progressive loss of renal function. Such dysfunction is associated with leukocyte infiltration in the glomerular and tubulointerstitial compartments in both human and experimental lupus nephritis. In this study, we investigated the role of the Ccr1 chemokine receptor in this infiltration process during the progression of nephritis in the lupus-prone New Zealand Black/New Zealand White (NZB/W) mouse model. We found that peripheral T cells, mononuclear phagocytes, and neutrophils, but not B cells, from nephritic NZB/W mice were more responsive to Ccr1 ligands than the leukocytes from younger prenephritic NZB/W mice. Short-term treatment of nephritic NZB/W mice with the orally available Ccr1 antagonist BL5923 decreased renal infiltration by T cells and macrophages. Longer Ccr1 blockade decreased kidney accumulation of effector/memory CD4(+) T cells, Ly6C(+) monocytes, and both M1 and M2 macrophages; reduced tubulointerstitial and glomerular injuries; delayed fatal proteinuria; and prolonged animal lifespan. In contrast, renal humoral immunity was unaffected in BL5923-treated mice, which reflected the unchanged numbers of infiltrated B cells in the kidneys. Altogether, these findings define a pivotal role for Ccr1 in the recruitment of T and mononuclear phagocyte cells to inflamed kidneys of NZB/W mice, which in turn contribute to the progression of renal injury.

Fanconi anemia and solid malignancies in childhood: a national retrospective study.

BACKGROUND: Fanconi anemia (FA) predisposes to hematologic disorders and myeloid neoplasia in childhood and to solid cancers, mainly oral carcinomas, in early adulthood. Few cases of solid cancers have been reported in childhood. PROCEDURES: We conducted a national retrospective study of solid tumors occurring in patients registered with or determined to have FA during childhood in France. Phenotypic features, tumor type, cancer treatment, and outcome were analyzed. Whenever available, fresh-frozen tumors were analyzed by microarray-based comparative genomics hybridization. RESULTS: We identified eight patients with FA with solid tumor from 1986 to 2012. For two patients, the diagnosis of FA was unknown at the time of cancer diagnosis. Moreover, we identified one fetus with a brain tumor. All patients showed failure to thrive and had dysmorphic features and abnormal skin pigmentation. Seven patients had BRCA2/FANCD1 mutations; five of these featured more than one malignancy and the median age at the time of cancer diagnosis was 11 months (range 0.4-3 years). Solid tumor types included five nephroblastomas, two rhabdomyosarcomas, two neuroblastomas, and three brain tumors. Two children died from the toxic effects of chemotherapy, two patients from the cancer, and one patient from secondary leukemia. Only one BRCA2 patient was alive more than 3 years after diagnosis, after tailored chemotherapy. CONCLUSION: Solid tumors are rare in FA during childhood, except in patients with BRCA2/FANCD1 mutations. The proper genetic diagnosis is mandatory to tailor the treatment.

Cytomegalovirus infection can mimic genetic nephrotic syndrome: a case report.

BACKGROUND: Nephrotic syndrome is a relatively rare but serious condition in children. Infantile nephrotic syndrome often has a genetic origin; the treatment is then symptomatic, with a poor prognosis, and a rapid evolution to chronic kidney disease. However, non-genetic infantile nephrotic syndrome has been identified. Here we report for the first time in a child a nephrotic syndrome as the sole clinical expression of a cytomegalovirus infection. CASE PRESENTATION: The patient was 5 months old when he presented with a nephrotic syndrome. An exhaustive genetic testing was conducted and came back negative. A viral work-up only showed a positive cytomegalovirus PCR. Antiviral treatment lead to a complete remission of the nephrotic syndrome, with no requirement for steroid therapy. Renal function remained normal throughout follow-up. CONCLUSION: Nephrotic syndrome should always be carefully investigated in children. This observation reinforces the connection between viral infections and pediatric nephrotic syndrome, sparking more controversy about an infectious origin to childhood nephrotic disease.

Toxocara canis infection: Unusual trigger of systemic lupus erythematosus.

Infection by Toxocara canis can cause systemic vasculitis. We report here a unique case of systemic lupus erythematosus (SLE) triggered by T. canis infection. An 8-year-old girl was treated with albendazole therapy for common toxocariasis, but she developed two weeks later, asthenia, fever, infiltrated maculopapular eruption of the face, peripheral vascular disease with necrosis of the fingers and inflammatory anemia with proteinuria. Anti-nuclear, anti-DNA and anti-Sm antibodies positivity, together with minimal change nephritis with mesangial exclusive IgM deposit on renal biopsy and clinical relapse after initially successful steroid therapy, led to the diagnosis of SLE. T. canis infection can trigger systemic lupus but must also be ruled out of the differential diagnosis given its association with autoimmunity.

Intestinal congenital/infantile fibrosarcoma: a new clinico-pathological entity?

Congenital/infantile fibrosarcoma (IFS) is a relatively rare form of fibrosarcoma diagnosed at birth or during early years of life and that differs from its adult counterpart because of a more favorable behavior. IFS is also known as cellular congenital mesoblastic nephroma, when it affects the kidney and is often but not always characterized by the ETV6-NTRK3 fusion transcript. We report herein the first series of an exceptional tumor of the small intestine occurring in newborns. The four patients shared a stereotyped clinico-pathological presentation with early and acute onset, intestinal perforation, and an infiltration by a highly cellular spindle cell tumor within the dilated intestinal wall exhibiting pathologic features typical of IFS. Molecular studies for the ETV6-NTRK3 translocation were negative in the three cases tested. Patients were treated by surgical wide resection alone and are alive and well (follow-up: 36 months-25 years). Thus, this new clinico-pathological entity, even with lack of documented evidence of the ETV6-NTRK3 translocation, should be included in the differential diagnosis of congenital bowel perforation or obstruction and may represent an intestinal counterpart of IFS.

A variant pattern of calretinin immunohistochemistry on rectal suction-biopsies is fully specific of short-segment Hirschsprung's disease.

BACKGROUND/PURPOSE: Calretinin immunohistochemistry is now widely used to diagnose Hirschsprung's disease (HD), since loss of calretinin expression within the mucosa and muscularis mucosae of rectal suction-biopsy is pathognomonic of HD. However, a stippled staining may be observed within hypertrophic nerves in the submucosae in some HD patients. The aim of the study was to test the hypothesis that such findings may announce the beginning of the transitional zone. METHODS: We retrieved 44 consecutive patients (10 girls and 34 boys; median age 6.5 days), diagnosed with aganglionosis on rectal suction biopsies, followed by surgery. According to calretinin immunohistochemistry performed on all paraffin-embedded rectal biopsies, we defined two HD groups: P- showing an absence of any staining within mucosa, muscularis mucosae and submucosa et P+ showing an absence of staining within the mucosa and muscularis mucosae, but a positivity of some submucosal hypertrophic nerves. These data were correlated to the length of total pathological segment (aganglionic and transitional zones) obtained from the original surgery reports. RESULTS: 18/44 patients (40.9 %) belonged to the P+ group and 26/44 (59 %) patients were within the P- group. In the P+ group, the maximal length of the aganglionic zone was 9 cm [mean 4 (1-9)] and the total pathological zone never exceeded 14 cm [mean 8 (3.8-14)]. In the P- group, the maximal length of aganglionic zone was 55.5 cm [mean 11.3 (2.5; 55.5)] and the total pathological zone extended to 59.5 cm [mean 17.75 (4.5; 59.5)]. Aganglionic segment was significantly shorter in the P+ group (p < 0.0001). CONCLUSION: Staining of some hypertrophic nerves in the submucosa in suction rectal biopsy of HD patients using calretinin immunohistochemistry is only encountered in short-segment aganglionosis with a pathological zone always restricted to rectal and sigmoid colon. This information could be crucial for the surgeons in the decision to choose a transanal procedure.

Neonatal cancer.

Neonatal cancer is rare and comprises a heterogeneous group of neoplasms with substantial histological diversity. Almost all types of paediatric cancer can occur in fetuses and neonates; however, the presentation and behaviour of neonatal tumours often differs from that in older children, leading to differences in diagnosis and management. The causes of neonatal cancer are unclear, but genetic factors probably have a key role. Other congenital abnormalities are frequently present. Teratoma and neuroblastoma are the most common histological types of neonatal cancer, with soft-tissue sarcoma, leukaemia, renal tumours, and brain tumours also among the more frequent types. Prenatal detection, most often on routine ultrasound or in the context of a known predisposition syndrome, is becoming more common. Treatment options pose challenges because of the particular vulnerability of the population. Neonatal cancer raises diagnostic, therapeutic, and ethical issues, and management requires a multidisciplinary approach.

Abnormal activation of autophagy-induced crinophagy in Paneth cells from patients with Crohn's disease.

Autophagy-related 16 like-1 (ATG16L-1), immunity-related GTPase-M (IRGM), and nucleotide-binding oligomerization domain-containing 2 (NOD2) regulate autophagy, and variants in these genes have been associated with predisposition to Crohn's disease (CD). However, little is known about the role of autophagy in CD. Intestinal biopsies from untreated pediatric patients with CD, celiac disease, or ulcerative colitis were analyzed by immunohistochemistry and electron microscopy. We observed that autophagy was specifically activated in Paneth cells from patients with CD, independently of mucosal inflammation or disease-associated variants of ATG16L1 or IRGM. In these cells, activation of autophagy was associated with a significant decrease in number of secretory granules and features of crinophagy. These observations might account for the disorganization of secretory granules previously reported in Paneth cells from patients with CD.

Peripheral neuroblastic tumors with genotype-phenotype discordance: a report from the Children's Oncology Group and the International Neuroblastoma Pathology Committee.

BACKGROUND: Of 4,706 peripheral neuroblastic tumors (pNTs) registered on the Children's Cancer Group and Children's Oncology Group Neuroblastoma Study between 1989 and 2010, 51 cases (1.1%) had genotype-phenotype discordance characterized by MYCN amplification (indicating poor prognosis) and Favorable Histology (indicating better prognosis). PROCEDURE: To distinguish prognostic subgroups in the genotype-phenotype discordant pNTs, two subgroups, "conventional" and "bull's eye," were identified based on the nuclear morphology. The "conventional" tumors (35 cases) included: Neuroblastoma, poorly differentiated subtype (NB-PD, 26 cases) with "salt-and-pepper" nuclei; neuroblastoma, differentiating subtype (4 cases); ganglioneuroblastoma, intermixed (3 cases); and ganglioneuroma, maturing subtype (2 cases). The "bull's eye" tumors included NB-PD with prominent nucleoli (16 cases). Clinicopathologic characteristics of these two subgroups were analyzed. N-myc protein expression was tested immunohistochemically on available tumors. RESULTS: No significant difference was found between these two subgroups in the distribution of prognostic factors such as age at diagnosis, clinical stage, histopathology category/subtype, mitosis-karyorrhexis index, ploidy, 1p LOH, and unbalanced 11q LOH. However, prognosis of the patients with "conventional" tumors (5-year EFS 85.7 ± 12.2%; OS 89.3 ± 10.3%) was significantly better than those with "bull's eye" tumors (EFS 31.3 ± 13.0%; OS 42.9 ± 16.2%; P = 0.0010 and 0.0008, respectively). Immunohistochemically all (11/11) tested "conventional" tumors were negative, and 10/11 tested "bull's eye" tumors were positive for N-myc protein expression. CONCLUSIONS: Based on the presence or absence of prominent nucleoli (the putative site of RNA synthesis/accumulation leading to N-myc protein expression), two prognostic subgroups, "conventional" with a better prognosis and "bull's eye" with a poor prognosis, were distinguished among the genotype-phenotype discordant pNTs.