Ad Ramsay

PAX3-FKHR Induces Morphological Change and Enhances Cellular Proliferation and Invasion in Rhabdomyosarcoma

Alveolar rhabdomyosarcoma (ARMS) is consistently associated with the characteristic translocations t(2;13)(q35;q14) and t(1;13)(p36;q14), which encode for the PAX3-FKHR and PAX7-FKHR fusion oncoproteins respectively. We have investigated the relationship between PAX3-FKHR expression and ARMS histogenesis in primary tumors and cell culture systems. In a blinded histological review of discrepant primary tumors in which there was PAX3-FKHR expression but embryonal histology, we found small areas of alveolar histology in 6 of 11 cases. This suggests that histology alone may under-represent the association between PAX3-FKHR and ARMS, and we investigated this link by examining the effect of ectopic PAX3-FKHR expression on RMS cells. Two cell lines, RD and HX170C, were stably transfected with a PAX3-FKHR expression construct. In cloned transfectants derived from both lines, PAX3-FKHR expression resulted in increased proliferative rate in vitro and promoted cell growth in the absence of added growth factors. Tumors that formed as xenografts in immunodeficient mice were faster growing, more locally invasive, and had a denser, more pleomorphic architecture than untransfected or empty vector transfected tumors. The characteristic clefts and alveolar spaces of ARMS, however, were not seen. In contrast, tumors grown as xenografts from individual clones derived from ARMS cell lines showed all of the classical morphological features of ARMS suggesting divergence in vivo from precursor cells propagated in culture.

Isolated EBV lymphoproliferative disease in a child with Wiskott-Aldrich syndrome manifesting as cutaneous lymphomatoid granulomatosis and responsive to anti-CD20 immunotherapy

Patients with primary immunodeficiencies such as the Wiskott-Aldrich syndrome (WAS) are prone to develop Epstein-Barr virus (EBV) related lymphoproliferative disorders (LPDs). EBV LPD is most frequently seen in patients receiving immunosuppressive treatment after organ transplantation (post-transplant lymphoproliferative disorder), but can also arise in the primary immunodeficiencies. Typically, EBV LPD presents as a diffuse systemic disease with lymphadenopathy and organ involvement. A rare angiocentric and angiodestructive form of EBV associated B cell LPD, lymphomatoid granulomatosis (LyG), has also been reported in association with WAS. LyG most commonly involves the lung, but can also be seen in brain, kidney, liver, and skin. This report describes the case of a 16 year old boy with WAS who presented with an isolated non-healing ulcerating skin lesion. Biopsy revealed an EBV related LPD with the histological features of LyG. This cutaneous lesion responded dramatically to treatment with specific anti-CD20 immunotherapy and the patient remains clinically free of LPD at 18 months.

Beta-catenin expression in pediatric fibroblastic and myofibroblastic lesions: A study of 100 cases

Nuclear immunoreactivity for β-catenin is a useful adjunct for diagnosis of adult desmoid-type fibromatoses, many of which exhibit mutations within the APC/β-catenin (Wnt) pathway. Pediatric fibromatoses represent a heterogeneous group of lesions that are diagnostically challenging, especially on biopsy. We studied β-catenin expression in a variety of pediatric fibroblastic and myofibroblastic lesions. Immunohistochemical nuclear expression of β-catenin was assessed in 100 tumors. High-level expression of β-catenin was found in 42% of usual-type or deep fibromatoses (21 of 50). Such expression was not seen in any of the other lesions, including fibrous hamartoma of infancy (0 of 18), juvenile hyaline fibromatosis (0 of 7), infantile digital fibromatosis (0 of 6), myofibromatosis (0 of 5), lipofibromatosis (0 of 4), calcifying aponeurotic fibroma (0 of 3), palmar-plantar fibromatosis (0 of 2), fibromatosis colli (0 of 1), or torticollis (0 of 1). High-level β-catenin staining is seen in deep “adult-type” fibromatoses occurring in children, although to a lesser frequency than in adult fibromatoses. This indicates that a subset of deep fibromatoses in childhood shares similar mechanisms of tumorigenesis with those in adults. β-catenin is not expressed in other common pediatric fibroblastic and myofibroblastic lesions, and the Wnt pathway does not appear to play a role in their pathogenesis.

Aberrant immunohistochemical expression in nonrhabdomyosarcoma soft tissue sarcomas of infancy: retrospective review of clinical material.

Malignant soft tissue tumors other than rhabdomyosarcoma (RMS) are uncommon in infancy, representing approximately 5% of pediatric sarcomas. The pathological categorization of non-RMS soft tissue malignancies from these young patients is complicated by variation in both morphologic and immunohistochemical features. A search covering an 11-year period identified 19 patients presenting at birth or in infancy with a clinical or referral diagnosis of soft tissue sarcoma. After histologic and immunohistochemical review, nine of these tumors were classified as primitive neuroectodermal tumor (PNET), three as infantile hemangiopericytoma (HPC), two as infantile fibrosarcoma (FS), and five as undifferentiated sarcoma. Those identified as undifferentiated sarcomas showed an atypical spindle and ovoid cell morphology, with cellular pleomorphism and high mitotic rate, but lacking the fascicular growth pattern of classic infantile fibrosarcoma. Immunohistochemical staining in this group showed variable weak positivity for a range of markers (desmin, smooth muscle actin, Myo-D1, PGP, NSE, S100, CO56, cytokeratin, and CD99), and did not fit readily into any distinct diagnostic category. In this series, tumors classified as soft tissue PNETs had a poor prognosis despite aggressive treatment. However, once RMS, PNET, and other rare specific lesions are excluded, the remaining undifferentiated sarcomas, despite their unusual morphology and immunohistochemistry, appear to behave in a similar favorable manner to infantile fibrosarcoma.

SACROCOCCYGEAL TUMORS IN INFANCY AND CHILDHOOD; A RETROSPECTIVE HISTOPATHOLOGICAL REVIEW OF 85 CASES

This study retrospectively examines the spectrum of sacrococcygeal tumors reported in a tertiary paediatric pathology department during a 15-year period. There were 85 sacrococcygeal tumors identified in total, including 79 (93%) sacrococcygeal germ cell tumors, of which 62 (78%) were benign, whereas 17 (22%) contained malignant yolk sac tumor elements. The median age at examination in cases with malignant elements present was significantly greater than in those with benign sacrococcygeal teratoma only (median 2 years, range birth—3 years versus median 1 week, range birth—10 years, respectively; p < .01). Of the 85 cases of total sacrococcygeal lesions 6 (7%) represented pathologies other than sacrococcygeal teratoma, including one case each of neuroblastoma, ganglioneuroma, myxopapillary ependymoma, primitive neuroectodermal tumor, lipomatous tumor, and unclassifiable inflammatory tumor. Of these 6 cases 3 were malignant (50%) compared with 17 of the 79 cases of sacrococcygeal germ cell tumors (22%; Z = 1.59, p = .08). The median age in the group of non-germ-cell sacrococcygeal masses was 3 years (range 5 months to 13 years).

Sclerosing Rhabdomyosarcoma in Childhood: Case Report and Review of the Literature

Rhabdomyosarcoma is the most common soft tissue malignancy in children but is rare in adults. The latest World Health Organization classification of soft tissue tumors recognizes embryonal, alveolar, and pleomorphic rhabdomyosarcomas. More recently, a sclerosing variant of rhabdomyosarcoma has been recognized and reported in seven adult patients. We describe a pediatric case of sclerosing rhabdomyosarcoma presenting as a sacral mass in a 3-year-old girl. Morphologically, the tumor showed a prominent sclerosing hyaline matrix and demonstrated pseudovascular and microalveolar architectural foci. Focal positivity was seen with desmin, smooth muscle actin, and myogenin. MyoD1 showed uniform diffuse nuclear staining. Fusion transcripts were not demonstrated by reverse transcriptase-polymerase chain reaction analysis. The histology, immunohistochemistry, and molecular genetics matched those reported in the seven adult cases of sclerosing rhabdomyosarcoma. This is the first case report, to our knowledge, of this rare tumor arising in the pediatric age group, and we compare the features with those reported in adult sclerosing rhabdomyosarcoma.

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 α-fetoprotein and α-1-antitrypsin. Our results indicate that the majority of hepatoblastomas expressed cytokeratins (10/12) and that α-1-antitrypsin and α-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.

Gains of Chromosome 8 in Pleuropulmonary Blastomas of Childhood

Vargas et al. [1] recently reported their experience with two cases of childhood pleuropulmonary blastomas (PPB), in addition to several further cases from the literature, with regard to the presence of chromosome 8 gains detected by fluorescence in situ hybridization (FISH) and karyotyping. We wish to add further information from an additional four unreported cases of childhood PPB in which paraffin-embedded and freshfrozen tissues were available for study. In each case, tissue sections stained with hematoxylin & eosin were assessed to examine the morphological features and interphase FISH was carried out using a chromosome 7/8 probe cocktail. The clinical details and FISH results are summarized in Table 1. In all cases, sections demonstrated the predominant appearance of sheets of blastema composed of small round blue cells, with a variably pleomorphic spindle cell component and cystic areas. In three of the four cases, trisomy 8 was detected by FISH. The other case demonstrated apparent tetraploidy, with four copies present per cell of the markers examined. In combination with the results presented by Vargas et al. [1], all 15 cases of PPB appear to show chromosome 8 gains, however, several additional chromosomal abnormalities may be present, including apparent tetraploidy. Our results further support the hypothesis that childhood PPB demonstrate characteristic clinicopathological diagnostic features. The finding that chromosome 8 gains are present in the majority, if not all, cases raises the issue of the diagnostic use of interphase FISH in such cases. Although the finding of trisomy 8 is not specific for this tumor, being found in several other pediatric solid malignancies, as stated in the previous report [1], in clinical practice, the finding of trisomy 8 in a childhood thoracic tumor with compatible morphological features lends considerable support to the diagnosis of PPB. Interphase FISH for precisely this purpose has been employed by us and may be particularly useful in the context of biopsy interpretation in which the architectural features and biphasic nature of the lesion may not be immediately apparent on routine morphological sections.

Intravascular inflammatory myofibroblastic tumors in infancy.

Inflammatory myofibroblastic tumor (IMT), previously described as inflammatory pseudotumor, can occur at any age but is a recognized soft tissue tumor of childhood. Less than 10 previous cases have been described of IMT affecting the heart, in patients ranging from 5 months to 17 years of age. We present three unusual, but similar, cases of IMT in infants, which were all predominantly intravascular in location, one of which was associated with death due to angiodestructive lesions of the coronary and cerebral arteries. These cases demonstrate an apparently distinct phenotype, with a predominant intravascular location of the tumor. Furthermore, this series highlights the difficulty in categorizing such lesions as benign versus malignant on histological grounds alone. IMT should be considered in the differential diagnosis of unusual pediatric intravascular spindle cell lesions.

Extensive Posttreatment Ganglioneuromatous Differentiation of Rhabdomyosarcoma: Malignant Ectomesenchymoma in an Infant

An 18-month-old boy presented initially with a 4-month history of gradually increasing swelling of the upper lip. The swelling was noted by the parents but appeared nontender and there were no associated local or systemic symptoms. Past medical history was unremarkable and there was no significant family history. On examination, there was a firm, nontender, nonfluctuant swelling affecting the soft tissue beneath the skin of the upper lip, approximately 2 cm in diameter. There was no significant cervical lymphadenopathy or other abnormal findings on physical examination. An incisional biopsy (1.0 0.5 cm) was performed, which demonstrated fibroadipose tissue and striated muscle with infiltration by sheets of tumor composed of small ovoid cells, some with a small amount of eosinophilic cytoplasm, with moderate nuclear pleomorphism and hyperchromasia, within a loose stromal background (Fig. 1). The tumor cells showed intense desmin expression (Fig. 2) and also stained strongly with Myogenin and MyoD1. No tumor cells stained positively with epithelial markers or NB84. A diagnosis of embryonal rhabdomyosarcoma was made and chemotherapeutic treatment administered in accordance with local rhabdomyosarcoma protocol (MMT95). The mass initially reduced in size to become almost impalpable but, 1 year later, a firm, nontender, slowgrowing mass, approximately 1 cm in diameter, had recurred at the site of the initial lesion. A further biopsy was carried out which now demonstrated the lesion to be composed of spindle cell stroma with intermixed clusters of differentiated ganglion cells (Fig. 3). No immature neuroblasts or rhabdomyoblasts could be identified. Immunohistochemical staining revealed strong expression of NCAM/CD56, neurofilaments, and S100 protein, but no cells stained positively with NB84 or desmin. The diagnosis was therefore that of infantile malignant ectomesenchymoma. Retrospective review and immunostaining of the original biopsy revealed scattered neurofilament-positive cells among the rhabdomyosarcomatous elements.