Pediatric extra-renal rhabdoid tumors with unusual morphology: A diagnostic pitfall for small biopsies

WT1 and Cyclin D1 Immunohistochemistry: A Useful Adjunct for Diagnosis of Pediatric Small Round Blue Cell Tumors on Small Biopsies

Pediatric small round blue cell tumors (SRBCTs) are a heterogeneous group of neoplasms with overlapping morphological appearance. Accordingly, their diagnosis is one of the most difficult in the field of surgical pathology. The most common tumors include rhabdomyosarcoma, Ewing’s sarcoma, neuroblastoma, lymphoblastic lymphoma and Wilms’ tumor (the blastemal component). Over time their diagnosis has become more difficult due to the increasing use of small biopsies. However, the advent of immunohistochemistry has improved the quality of diagnosis in most cases by the application of an adequate panel of immunomarkers. Recently, WT1 and Cyclin D1 have been shown to be useful in the differential diagnosis of SRBCTs on surgically-resected specimens, showing a diffuse cytoplasmic positivity of the former in all RMSs and a diffuse nuclear staining of the latter in both EWS and NB. The aim of the present study was to investigate the expression of WT1 and Cyclin D1 on small biopsies from a series of 105 pediatric SRBCTs to evaluate their diagnostic utility. Both immunomarkers were differentially expressed, with a diffuse and strong cytoplasmic staining for WT1 limited to all cases of RMS, and a diffuse nuclear staining for cyclin D1 restricted to all cases of EWS and NB. Notably, the expression of WT1 and cyclin D1 was also retained in those cases in which the conventional tumor markers (myogenin, desmin and MyoD1 for RMS; CD99 for EWS; NB84 for NB) were focally expressed or more rarely absent. The present study shows that WT1 and Cyclin D1 are helpful immunomarkers exploitable in the differential diagnosis of pediatric SRBCTs on small biopsies, suggesting their applicability in routine practice.

SMARCB1-deficient Tumors of Childhood: A Practical Guide

The SMARCB1 gene ( INI1, BAF47) is a member of the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex, involved in the epigenetic regulation of gene transcription. SMARCB1 acts as a tumor suppressor gene, and loss of function of both alleles gives rise to SMARCB1-deficient tumors. The prototypical SMARCB1-deficient tumor is the malignant rhabdoid tumor (MRT) which was first described in the kidney but also occurs in soft tissue, viscera, and the brain (where it is referred to as atypical teratoid rhabdoid tumor or AT/RT). These are overwhelmingly tumors of the very young, and most follow an aggressive and ultimately lethal course. Morphologically, most but not all contain a population of "rhabdoid" cells, which are large cells with abundant cytoplasm, perinuclear spherical inclusions, and eccentric vesicular nuclei with large inclusion-like nucleoli. MRT immunohistochemistry reveals complete loss of SMARCB1 nuclear expression, and molecular analysis confirms biallelic SMARCB1 inactivation in the vast majority. Rare AT/RTs have loss of SMARCA4, another SWI/SNF member, rather than SMARCB1. With the widespread adoption of SMARCB1 immunohistochemistry, an increasing number of SMARCB1-deficient tumors outside of the MRT-AT/RT spectrum have been described. In addition to MRT and AT/RT, pediatric tumors with complete loss of SMARCB1 expression include cribriform neuroepithelial tumor, renal medullary carcinoma, and epithelioid sarcoma. Tumors with variable loss of SMARCB1 expression include subsets of epithelioid malignant peripheral nerve sheath tumor, schwannomas arising in schwannomatosis, subsets of chordomas, myoepithelial carcinomas, and sinonasal carcinomas. Variable and reduced expression of SMARCB1 is characteristic of synovial sarcoma. In this review, the historical background, clinical characteristics, morphology, immunohistochemical features, and molecular genetics most germane to these tumors are summarized. In addition, familial occurrence of these tumors (the rhabdoid tumor predisposition syndrome) is discussed. It is hoped that this review may provide practical guidance to pathologists encountering tumors that have altered expression of SMARCB1.

Primary Osteosarcoma of the Bone with Rhabdoid Features: A Rare, Previously Undescribed Primary Malignant Tumor of Bone

Primary osteosarcoma of the bone with rhabdoid features is a rare malignant tumor of bone, not previously described in the literature. Here we report a 69-year-old female who originally presented with a right femur pathologic fracture. Radiographs of the injury showed an aggressive-appearing lesion of the distal femur. Initial biopsy was done, which was not diagnostic; additional advanced imaging studies were performed, which failed to show any other site within the body with detectable disease process. Accordingly, the patient underwent radical resection of the distal femur and reconstruction with endoprosthesis. Histopathology obtained from the operative specimen showed osteosarcoma with rhabdoid features. Two months after surgery, the patient is symptom-free and doing well; she is currently pending adjuvant chemotherapy. Although rhabdoid features have been described in extraskeletal osteosarcoma, this appears to be the first mention of osteosarcoma of bone with rhabdoid features in the literature.

Diagnostic utility of cyclin D1 in the diagnosis of small round blue cell tumors in children and adolescents

Small round blue cell tumors (SRBCTs) of children and adolescents are often diagnostically challenging lesions. With the increasing diagnostic approach based on small biopsies, there is the need of specific immunomarkers that can help in the differential diagnosis among the different tumor histotypes to assure the patient a correct diagnosis for proper treatment. Based on our recent studies showing cyclin D1 overexpression in both Ewing sarcoma/primitive peripheral neuroectodermal tumor (EWS/pPNET) and peripheral neuroblastic tumors (neuroblastoma and ganglioneuroblastoma), we immunohistochemically assessed cyclin D1 immunoreactivity in 128 cases of SRBCTs in children and adolescents to establish its potential utility in the differential diagnosis. All cases of EWS/pPNET and the undifferentiated/poorly differentiated neuroblastomatous component of all peripheral neuroblastic tumors exhibited strong and diffuse nuclear staining (>50% of neoplastic cells) for cyclin D1. In contrast, this marker was absent from rhabdomyosarcoma (regardless of subtype) and lymphoblastic lymphoma (either B- or T-cell precursors), whereas it was only focally detected (<5% of neoplastic cells) in some cases of Wilms tumor (blastemal component) and desmoplastic small round cell tumor. Our findings suggest that cyclin D1 can be exploitable as a diagnostic adjunct to conventional markers in confirming the diagnosis of EWS/pPNET or neuroblastoma/ganglioneuroblastoma. Its use in routine practice may also be helpful for those cases of SRBCT with undifferentiated morphology that are difficult to diagnose after application of the conventional markers.

Cyclin D1 and Ewing's sarcoma/PNET: A microarray analysis

Recent immunohistochemical analyses have showed that cyclin D1 is expressed in soft tissue Ewing's sarcoma/peripheral neuroectodermal tumor (PNET) of childhood and adolescents, while it is undetectable in both embryonal and alveolar rhabdomyosarcoma. In the present paper, microarray analysis provided evidence of a significant upregulation of cyclin D1 in Ewing's sarcoma as compared to normal tissues. In addition, we confirmed our previous findings of a significant over-expression of cyclin D1 in Ewing sarcoma as compared to rhabdomyosarcoma. Bioinformatic analysis also allowed to identify some other genes, strongly correlated to cyclin D1, which, although not previously studied in pediatric tumors, could represent novel markers for the diagnosis and prognosis of Ewing's sarcoma/PNET. The data herein provided support not only the use of cyclin D1 as a diagnostic marker of Ewing sarcoma/PNET but also the possibility of using drugs targeting cyclin D1 as potential therapeutic strategies.

Atypical teratoid/ rhabdoid tumor, an immunohistochemical study of potential diagnostic and prognostic markers

Atypical teratoid/rhabdoid tumor (AT/RT) is a rare tumor of the CNS mostly seen in infants and is often associated with a dismal outcome. Despite the heterogeneous morphology and/or immunoprofile, its diagnosis nowadays relies on the negative INI-1/BAF47 nuclear immunostain in tumor cells. We aim to investigate a number of immunohistochemical antibodies as potential diagnostic and prognostic markers. All AT/RT cases in patients younger than 18 years of age were included. Demographics, clinical features and outcome were collected. Immunostains tested included SALL-4, OCT3/4, CD99, FLI-1, cyclin-D1, β-catenin, P53, P16, CDX2 and WT-1. Nineteen cases (10 males) were identified at our center between 2004-2013 with a median age of 24 months. Ten (52.6%) cases were supratentorial. Six (42.9%) cases showed metastasis at time of presentation. Chemotherapy was administered to 10 (62.5%) and radiotherapy to seven (43.8%). The median overall survival was 11 months. A single long-term survival of 104 months was identified. Pathologically, most cases showed an admixture of rhabdoid cells and/or small cells and/or pale cells in variable proportions. Of all tested antibodies, only positivity for FLI-1 was associated with improved survival (P = 0.0012), while positivity for cyclin-D1 showed a trend toward improved survival (P = 0.0547). CDX2 was positive only in the single long-term survival. Interestingly, two cases showed co-expression of CD99 and FLI-1, and some were positive for SALL-4. In conclusion, FLI-1 and cyclin-D1 are potential prognostic markers associated with better outcome. Occasional AT/RT cases might co-express CD99 and FLI-1 as well as SALL-4, a potential diagnostic pitfall with Ewing sarcoma/ primitive neuroectodermal tumors and germ cell tumors, respectively.

Immunohistochemistry as potential diagnostic pitfall in the most common solid tumors of children and adolescents

Making a correct diagnosis when dealing with a small round blue cell tumor (SRBCT) of children and adolescents may be relatively straightforward if the tumor arises in the typical clinical setting and the classic pathologic features are all recognizable. However it is widely known that diagnostic difficulties may arise because of: (i) many tumors share overlapping morphological and/or immunohistochemical features; (ii) considerable clinical, pathologic, and immunohistochemical variations do exist; (iii) the increasing use of small biopsies in daily practice makes the diagnosis of these neoplasms more challenging. Accordingly, immunohistochemical analyses are currently mandatory in establishing the correct diagnosis. In this regard there is the need to identify more sensitive and specific immunomarkers useful in the distinction of the several tumor entities. Over the last decades, several markers, such as CD99, WT1 protein, desmin, myogenin, NB84, and INI1 have been identified, providing a considerable help in recognition of the most common solid tumors (ESW/pPNET, rhabdomyosarcoma, neuroblastoma, Wilms' tumor, desmoplastic small round cell tumor; malignant rhabdoid tumor) in children and adolescents. However, at the same time, their unusual, unexpected expression can result in a misinterpretation of the immunohistochemical results, especially by pathologists who are not familiar with oncologic pediatric pathology. Therefore the present review focuses on the potential immunohistochemical pitfalls which should be kept in mind by pathologists to prevent diagnostic errors when dealing with SRBCTs.

Cyclin D1 is a useful marker for soft tissue Ewing's sarcoma/peripheral Primitive Neuroectodermal Tumor in children and adolescents: A comparative immunohistochemical study with rhabdomyosarcoma

Cyclin D1 amplification and/or overexpression contribute to the loss of the regulatory circuits that govern G1-S transition phase of the cell cycle, playing pivotal roles in different human malignant tumors, including breast, colon, prostate cancer, lymphoma, melanoma and neuroblastoma. In vitro studies have shown that cyclin D1 is overexpressed in Ewing's sarcoma (EWS)/peripheral Primitive Neuroectodermal Tumor (pPNET), but not in rhabdomyosarcoma cell lines. Only a few immunohistochemical studies are available on cyclin D1 expression in EWS/pPNET, which confirmed its expression only in a limited number of cases. The aim of the present study was a comparative immunohistochemical analysis of the expression and distribution of cyclin D1 in a large series of pediatric/adolescent soft tissue EWS/pPNETs and rhabdomyosarcomas (both embryonal and alveolar subtypes) to assess its potential usefulness in their differential diagnosis. Notably cyclin D1 was strongly and diffusely expressed in all cases (20/20) of EWS/pPNET, while it was lacked in all cases (15/15) of rhabdomyosarcomas. Immunohistochemical overexpression of cyclin D1 in EWS/pPNET is a novel finding which could be exploitable as a diagnostic immunomarker for this tumor. Although highly sensitive, cyclin D1 is not specific for EWS/pPNET, and thus it should not be evaluated alone but in the context of a wide immunohistochemical panel. Accordingly, we first emphasize that when pathologists are dealing with a small round blue cell tumor of soft tissues in pediatric/adolescent patients, a strong and diffuse nuclear expression of cyclin D1 is of complementary diagnostic value to CD99 and FLI-1 in confirming diagnosis of EWS/pPNET and in ruling out rhabdomyosarcoma.

Oncofetal expression of Wilms' tumor 1 (WT1) protein in human fetal, adult and neoplastic skeletal muscle tissues

There is increasing evidence that WT1 protein expression is found not only at nuclear, but also at cytoplasmic, level in several developing and neoplastic tissues. In order to better understand the possible role of WT1 protein in human skeletal myogenesis and oncogenesis of rhabdomyosarcoma, we assessed immunohistochemically its comparative expression in a large series of human developing, adult and neoplastic skeletal muscle tissues. The present study shows that WT1 protein is developmentally expressed in the cytoplasm of human myoblasts from the 6 weeks of gestational age. This expression was maintained in the myotubes of developing muscles of the trunk, head, neck, and extremities, while it was down-regulated in fetal skeletal fibers from 20 weeks of gestational age as well as in adult normal skeletal muscle. Notably, WT1 immunostaining disappeared from rhabdomyomas, whereas it was strongly and diffusely re-expressed in all cases (27/27) of embryonal and alveolar rhabdomyosarcoma. The comparative evaluation of the immunohistochemical findings revealed that WT1 cytoplasmic expression in rhabdomyosarcoma may represent an ontogenetic reversal, and this nuclear transcription factor can also be considered an oncofetal protein which can be exploitable as an additional, highly sensitive immunomarker, together with desmin, myogenin and MyoD1, of this tumor. Moreover, our observations support the rationale for the use of WT1 protein-based target therapy in high risk rhabdomyosarcomas in children and adolescents.

Wilms tumor 1 (WT1) protein: Diagnostic utility in pediatric tumors

Despite Wilms tumor 1 (WT1) protein was originally considered as a specific immunomarker of Wilms tumor, with the increasing use of immunohistochemistry, there is evidence that other tumors may share WT1 protein expression. This review focuses on the immunohistochemical profile of WT1 protein in the most common malignant tumors of children and adolescents. The variable expression and distribution patterns (nuclear vs cytoplasmic) in the different tumors, dependent on the antibodies used (anti-C or N-terminus WT1 protein), will be emphasized by providing explicative illustrations. Potential diagnostic pitfalls from unexpected WT1 protein expression in some tumors will be discussed in order to avoid diagnostic errors, especially when dealing with small biopsies.

Towards an international pediatric liver tumor consensus classification: proceedings of the Los Angeles COG liver tumors symposium

Liver tumors are rare in children, and their diagnoses may be challenging particularly because of the lack of a current consensus classification system. Systematic central histopathological review of these tumors performed as part of the pediatric collaborative therapeutic protocols has allowed the identification of histologic subtypes with distinct clinical associations. As a result, histopathology has been incorporated within the Children's Oncology Group (COG) protocols, and only in the United States, as a risk-stratification parameter and for patient management. Therefore, the COG Liver Tumor Committee sponsored an International Pathology Symposium in March 2011 to discuss the histopathology and classification of pediatric liver tumors, and hepatoblastoma in particular, and work towards an International Pediatric Liver Tumors Consensus Classification that would be required for international collaborative projects. Twenty-two pathologists and experts in pediatric liver tumors, including those serving as central reviewers for the COG, European Société Internationale d'Oncologie Pédiatrique, Gesellschaft für Pädiatrische Onkologie und Hämatologie, and Japanese Study Group for Pediatric Liver Tumors protocols, as well as pediatric oncologists and surgeons specialized in this field, reviewed more than 50 pediatric liver tumor cases and discussed classic and newly reported entities, as well as criteria for their classification. This symposium represented the first collaborative step to develop a classification that may lead to a common treatment-stratification system incorporating tumor histopathology. A standardized, clinically meaningful classification will also be necessary to allow the integration of new biological parameters and to move towards clinical algorithms based on patient characteristics and tumor genetics, which should improve future patient management and outcome.

Soft tissue tumors of uncertain origin

Many soft tissue tumors of childhood lack obvious differentiation toward a defined mesenchymal tissue type or have a phenotype that does not correspond to any defined normal tissue. These challenging tumors are currently regarded as neoplasms of uncertain differentiation. Nonetheless, there have been great strides in the understanding of their pathologic and genetic features and biologic underpinnings. The application of new genetic information to the pathologic diagnosis among this group of tumors is an emerging area in diagnostic pediatric pathology. This article reviews the clinicopathologic features of tumors of uncertain and/or miscellaneous origin, with an emphasis on the unique aspects of these neoplasms in children and adolescents, use of diagnostic adjuncts, and differential diagnosis.

Renal primitive neuroectodermal tumor: does age at diagnosis impact outcomes?

Primitive neuroectodermal tumor (PNET) of the kidney is a rare and highly malignant neoplasm. The median age for renal PNET is 27 years but it can be seen also in a wide age range between 3 and 78 years. We performed a Medline search for the term renal PNET and identified 79 cases up till December of 2010. We report here a new case of renal PNET and a literature review for published data for evaluation of clinicopathological prognostic factors, with an emphasis on prognosis in two groups of adults and children-adolescents: 18 years of age or under and over 18 years.

Ewing sarcoma/peripheral primitive neuroectodermal tumor and related tumors

Ewing sarcoma/peripheral primitive neuroectodermal tumor (EWS/pPNET) and other tumors with EWS gene rearrangements encompass a malignant and intermediate neoplasm with a broad anatomic distribution and a wide age range but a predilection for soft tissue in children, adolescents, and young adults. The overlapping histologic, immunohistochemical and cytogenetic and molecular genetic features create diagnostic challenges despite significant clinical and prognostic differences. Ewing sarcoma is the 3rd most common sarcoma in children and adolescents, and desmoplastic small round cell tumor is a rare neoplasm that occurs more often in older children, adolescents, and young adults. Pathologic examination is complemented by immunohistochemistry, cytogenetics, and molecular genetics. This article reviews the clinicopathologic features of EWS/pPNET and desmoplastic small round cell tumor in the spectrum of tumors with EWS gene rearrangements. Other tumors with different histopathologic features and an EWS gene rearrangement are discussed elsewhere in this volume.

Extrarenal rhabdoid tumor mimicking a sacral peripheral nerve sheath tumor

Extrarenal rhabdoid tumor is a rare, highly aggressive tumor of childhood with a poor prognosis. It represents <1% of pediatric soft tissue malignancies, typically involving infants . Frequently involved extrarenal sites include deep locations of the neck, abdomen, and paraspinal regions. The presence of "rhabdoid" cells is the characteristic histologic feature. Recent discovery of a specific genetic mutation enables a more accurate diagnosis. We present a case in an adolescent of extrarenal rhabdoid tumor arising within the sacral canal. This appears to be the first reported case of an extrarenal rhabdoid tumor arising within the sacral canal and mimicking a peripheral nerve sheath tumor. While rare, this tumor can be included in the radiologic differential diagnosis of peripheral nerve sheath tumors in children.