Robin D. LeGallo

DICER1 mutations in childhood cystic nephroma and its relationship to DICER1-renal sarcoma.

The pathogenesis of cystic nephroma of the kidney has interested pathologists for over 50 years. Emerging from its initial designation as a type of unilateral multilocular cyst, cystic nephroma has been considered as either a developmental abnormality or a neoplasm or both. Many have viewed cystic nephroma as the benign end of the pathologic spectrum with cystic partially differentiated nephroblastoma and Wilms tumor, whereas others have considered it a mixed epithelial and stromal tumor. We hypothesize that cystic nephroma, like the pleuropulmonary blastoma in the lung, represents a spectrum of abnormal renal organogenesis with risk for malignant transformation. Here we studied DICER1 mutations in a cohort of 20 cystic nephromas and 6 cystic partially differentiated nephroblastomas, selected independently of a familial association with pleuropulmonary blastoma and describe four cases of sarcoma arising in cystic nephroma, which have a similarity to the solid areas of type II or III pleuropulmonary blastoma. The genetic analyses presented here confirm that DICER1 mutations are the major genetic event in the development of cystic nephroma. Further, cystic nephroma and pleuropulmonary blastoma have similar DICER1 loss of function and ‘hotspot’ missense mutation rates, which involve specific amino acids in the RNase IIIb domain. We propose an alternative pathway with the genetic pathogenesis of cystic nephroma and DICER1-renal sarcoma paralleling that of type I to type II/III malignant progression of pleuropulmonary blastoma.

PDGFR-A is a therapeutic target in alveolar rhabdomyosarcoma

Alveolar rhabdomyosarcoma is an aggressive skeletal muscle cancer of childhood. Our initial studies of rhabdomyosarcoma gene expression for patients enrolled in a national clinical trial suggested that platelet-derived growth factor receptor A (PDGFR-A) may be a mediator of disease progression and metastasis. Using our conditional mouse tumor models that authentically recapitulate the primary mutations and metastatic progression of alveolar rhabdomyosarcomas in humans, we found by immunoblotting and immunokinase assays that PDGFR-A and its downstream effectors, mitogen-activated protein kinase and Akt, were highly activated in both primary and metastatic tumors. Inhibition of PDGFR-A by RNA interference, small molecule inhibitor or neutralizing antibody had a dramatic effect on tumor cell growth both in vitro and in vivo, although resistance evolved in one-third of tumors. These results establish proof-of-principal for PDGFR-A as a therapeutic target in alveolar rhabdomyosarcoma.

Evasion Mechanisms to Igf1r Inhibition in Rhabdomyosarcoma

Inhibition of the insulin-like growth factor 1 receptor (Igf1r) is an approach being taken in clinical trials to overcome the dismal outcome for metastatic alveolar rhabdomyosarcoma (ARMS), an aggressive muscle cancer of children and young adults. In our study, we address the potential mechanism(s) of Igf1r inhibitor resistance that might be anticipated for patients. Using a genetically engineered mouse model of ARMS, validated for active Igf1r signaling, we show that the prototypic Igf1r inhibitor NVP-AEW541 can inhibit cell growth and induce apoptosis in vitro in association with decreased Akt and Mapk phosphorylation. However, drug resistance in vivo is more common and is accompanied by Igf1r overexpression, Mapk reactivation, and Her2 overexpression. Her2 is found to form heterodimers with Igf1r in resistant primary tumor cell cultures, and stimulation with Igf2 leads to Her2 phosphorylation. The Her2 inhibitor lapatinib cooperates with NVP-AEW541 to reduce Igf1r phosphorylation and to inhibit cell growth even though lapatinib alone has little effect on growth. These results point to the potential therapeutic importance of simultaneous targeting of Igf1r and Her2 to abrogate resistance. Mol Cancer Ther; 10(4); 697–707. ©2011 AACR.

Lineage of origin in rhabdomyosarcoma informs pharmacological response

Lineage or cell of origin of cancers is often unknown and thus is not a consideration in therapeutic approaches. Alveolar rhabdomyosarcoma (aRMS) is an aggressive childhood cancer for which the cell of origin remains debated. We used conditional genetic mouse models of aRMS to activate the pathognomonic Pax3:Foxo1 fusion oncogene and inactivate p53 in several stages of prenatal and postnatal muscle development. We reveal that lineage of origin significantly influences tumor histomorphology and sensitivity to targeted therapeutics. Furthermore, we uncovered differential transcriptional regulation of the Pax3:Foxo1 locus by tumor lineage of origin, which led us to identify the histone deacetylase inhibitor entinostat as a pharmacological agent for the potential conversion of Pax3:Foxo1-positive aRMS to a state akin to fusion-negative RMS through direct transcriptional suppression of Pax3:Foxo1.

DIAGNOSIS OF HYDATIDIFORM MOLES USING P57 IMMUNOHISTOCHEMISTRY AND HER2 FLUORESCENT IN SITU HYBRIDIZATION

Fluorescent in situ hybridization (FISH) for HER2 performed on paraffin-embedded tissue samples and immunohistochemical analysis for p57 may be useful ancillary studies to aid in the diagnosis and classification of hydatidiform moles (HMs). HER2 FISH was validated against 24 paraffin-embedded sections of HMs and hydropic abortions and showed an 85% concordance rate. A morphologic assessment based on 44 cases showed 25% disagreement between original and consensus diagnosis based on H&E-stained slides, all of which involved the differential diagnosis of partial mole and hydropic abortion. Immunohistochemical analysis for p57 and HER2 FISH were performed, and a final diagnosis was assigned by using the results from all ancillary studies. p57 staining was absent in 11 of 13 complete moles, and HER2 was triploid in 8 of 10 partial moles .HER2 FISH and immunohistochemical analysis for p57 are useful ancillary techniques in the evaluation of HM, especially when triploid content is seen.

B Cell Infiltration and Lymphonodular Hyperplasia in Bladder Submucosa of Patients With Persistent Bacteriuria and Recurrent Urinary Tract Infections

PURPOSEnWe defined chronic inflammatory cell types in bladder submucosa and the presence of umbrella cells on the surface of bladder epithelium in patients 5 to 21 years old with persistent bacteriuria due to neurogenic bladder and recurrent urinary tract infections associated with vesicoureteral reflux.nnnMATERIALS AND METHODSnBladder mucosa biopsies from 12 patients and 6 controls were fixed in Carnoys solution and examined for T cells (CD3, CD4, CD8), B cells (CD79) and plasma cells (CD138). The number of cells in a defined area of submucosa was determined by counting all nuclei in the area. A contiguous section was also stained for uroplakin expression with a monoclonal antibody against uroplakin III to ascertain the integrity of bladder umbrella cells.nnnRESULTSnB cells, plasma cells and lymphoid nodules were found only in patient biopsies. T cell expression was evident in patient and control biopsies. Uroplakin staining of surface epithelium was uniform from control biopsies but spotty or entirely absent from patient biopsies.nnnCONCLUSIONSnPatients with persistent bacteriuria or recurrent urinary tract infections had significant B cell infiltration in the submucosa, including lymphoid nodules. These inflammatory changes are likely due to antigenic stimulation from repeated exposure to bacteria. These changes are associated with frequent absence of uroplakin on surface epithelium.

Imaging characteristics of angiomatoid fibrous histiocytoma of bone

We present the first report of a patient with angiomatoid fibrous histiocytoma of bone in the radiology literature. This tumor initially eluded diagnosis due to its similarities with chronic hematoma and aneurysmal bone cyst. Only two cases of angiomatoid fibrous histiocytoma have been reported in the radiology literature and both of these lesions were in the soft tissues. The fairly distinctive findings in our patient of multiple large cystic chambers with fluid-fluid levels are similar to the findings in the two soft tissue case reports, suggesting that imaging may be used to suggest this specific diagnosis regardless of location, especially in the clinical setting of unexplained hematoma or anemia. Mention of this diagnosis in the radiology report may aid in the final diagnosis at pathology, because special techniques, including fluorescent in situ hybridization, must be applied in order to fully evaluate for the diagnosis.

Small patients, complex challenging cases: a reappraisal of the professional efforts in perinatal autopsies.

We, representing the Society for Pediatric Pathology (SPP), commend Dr Sinard and members of the Autopsy Committee of the College of American Pathologists (CAP) for writing the article ‘‘Accounting for the Professional Work of Pathologists Performing Autopsies’’ that was published in the February 2013 issue of Archives of Pathology & Laboratory Medicine. As compensation for pathologists’ services becomes more closely tied to productivity, the application of workload units to the performance of autopsies becomes vitally important for pathologists performing these critical, but nonreimbursed medical procedures. It is to the benefit of pathologists, hospitals, and patients to fairly and accurately quantify the time, work, and professional expertise required for autopsy performance and reporting. Determination of appropriate workload values is especially crucial for pathologists performing large numbers of autopsies, such as those who staff children’s hospitals or medical centers serving obstetric patients. The national hospital autopsy rate hovers around 5% and adult hospital autopsy rates range from around 10% to from 15% to 25% in some specialized medical centers; however, pediatric and maternity hospitals show significantly higher autopsy rates, ranging from 25% to 66%. The rates of postmortem examination of stillbirth and perinatal deaths range from 47% to 94% in academic settings, and from 53% to 77% in some special stillbirth programs. Moreover, as efforts to elucidate the causes and decrease the incidence of stillbirth remain prioritized clinical objectives, fetal autopsy rates will likely increase. Finally, the improved resolution of prenatal imaging techniques has not negated the need to evaluate anatomy and assess for acquired pathology in nonsurvivors through a competent postmortem examination.

Epiphyseal presentation of non-Hodgkin’s lymphoma of bone in two pediatric patients—one with primary lymphoma of bone

We report two children with lymphoma of bone centered in the distal femoral epiphysis who presented with knee pain. Radiographs, magnetic resonance imaging (MRI) and computed tomography (CT) were performed on both patients prior to biopsy. Following biopsy, both patients had fluorodeoxyglucose (18u2009F-FDG) positron emission tomography/CT (PET/CT) and whole-body technetium-99m (Tc-99m) scintigraphy performed for staging. One patient met the criteria for primary lymphoma of bone. One patient did not meet the criteria for primary lymphoma of bone because of PET uptake in a popliteal, external iliac and possibly lower abdominal node. Both patients responded well to chemotherapy and are disease free more than 7xa0years after diagnosis. While an epiphyseal presentation of lymphoma of bone is rare, the efficacy of treatment and the compromised outcome associated with diffuse spread of the disease make early recognition by clinicians important. We present these two cases to increase awareness of the disease and to have clinicians consider it in the differential diagnosis of adolescent epiphyseal lesions.

Relationships between preclinical course grades and standardized exam performance

AbstractnSuccess in residency matching is largely contingent upon standardized exam scores. Identifying predictors of standardized exam performance could promote primary intervention and lead to design insights for preclinical courses. We hypothesized that clinically relevant courses with an emphasis on higher-order cognitive understanding are most strongly associated with performance on United States Medical Licensing Examination Step exams and National Board of Medical Examiners clinical subject exams. Academic data from students between 2007 and 2012 were collected. Preclinical course scores and standardized exam scores were used for statistical modeling with multiple linear regression. Preclinical courses were categorized as having either a basic science or a clinical knowledge focus. Medical College Admissions Test scores were included as an additional predictive variable. The study sample comprised 795 graduating medical students. Median score on Step 1 was 234 (interquartile range 219–245.5), and 10.2xa0% (81/795) scored lower than one standard deviation below the national average (205). Pathology course score was the strongest predictor of performance on all clinical subject exams and Step exams, outperforming the Medical College Admissions Test in strength of association. Using Pathology score <75 as a screening metric for Step 1 score <205 results in sensitivity and specificity of 37 and 97xa0%, respectively, and a likelihood ratio of 11.9. Performance in Pathology, a clinically relevant course with case-based learning, is significantly related to subsequent performance on standardized exams. Multiple linear regression is useful for identifying courses that have potential as risk stratifiers.