Neonatal necrotizing enterocolitis: clinical considerations and pathogenetic concepts.

Necrotizing enterocolitis (NEC), a disease affecting predominantly premature infants, is a leading cause of morbidity and mortality in neonatal intensive care units. Although several predisposing factors have been identified, such as prematurity, enteral feeding, and infection, its pathogenesis remains elusive. In the past 20 years, we have established several animal models of NEC in rats and found several endogenous mediators, especially platelet-activating factor (PAF), which may play a pivotal role in NEC. Injection of PAF induces intestinal necrosis, and PAF antagonists prevent the bowel injury induced by bacterial endotoxin, hypoxia, or challenge with tumor necrosis factor-a (TNF) plus endotoxin in adult rats. The same is true for lesions induced by hypoxia and enteral feeding in neonatal animals. Human patients with NEC show high levels of PAF and decreased plasma PAF-acetylhydrolase, the enzyme degrading PAF. The initial event in our experimental models of NEC is probably polymorphonuclear leukocyte (PMN) activation and adhesion to venules in the intestine, which initiates a local inflammatory reaction involving proinflammatory mediators including TNF, complement, prostaglandins, and leukotriene C4. Subsequent norepinephrine release and mesenteric vasoconstriction result in splanchnic ischemia and reperfusion. Bacterial products (e.g., endotoxin) enter the intestinal tissue during local mucosal barrier breakdown, and endotoxin synergizes with PAF to amplify the inflammation. Reactive oxygen species produced by the activated leukocytes and by intestinal epithelial xanthine oxidase may be the final pathway for tissue injury. Protective mechanisms include nitric oxide produced by the constitutive (mainly neuronal) nitric oxide synthase, and indigenous probiotics such as Bifidobacteria infantis. The former maintains intestinal perfusion and the integrity of the mucosal barrier, and the latter keep virulent bacteria in check. The development of tissue injury depends on the balance between injurious and protective mechanisms.

Calcifying fibrous pseudotumor versus inflammatory myofibroblastic tumor: a histological and immunohistochemical comparison.

Calcifying fibrous pseudotumor (CFP), a recently described lesion, is characterized by a predominantly lymphoplasmacytic infiltrate with abundant hyalinized collagen and psammomatous or dystrophic calcifications. The cause and pathogenesis are unclear, but it has been postulated that CFP may represent a sclerosing end stage of inflammatory myofibroblastic tumor (IMT). We compared the histological and immunohistochemical profiles of seven cases diagnosed as CFP and seven as IMT. Histologically, the CFP demonstrated varying degrees of calcifications in addition to fibroblastic proliferation admixed with inflammatory cells composed of lymphocytes, eosinophils, and mast cells. The IMTs rarely contain calcifications and had a myofibroblastic proliferation varying from hyalinized acellular collagen to florid fibroblastic proliferations simulating sarcoma. The inflammatory component was composed primarily of plasma cells and lymphocytes, sometimes arranged as lymphoid aggregates with germinal centers. All CFP cases were diffusely positive for factor XIIIa and negative for smooth muscle actin, muscle-specific actin, and CD34. All IMTs demonstrated diffuse positivity for actin, variable positivity for CD34, and focal positivity for Factor XIIIa. This study demonstrates certain distinct histologic, immunohistochemical, and electron microscopic features between IMTs and CFPs.

Nasal chondromesenchymal hamartoma in children: report of 2 cases with review of the literature.

Hamartoma in the nasal cavity of children is especially rare. Most documented cases occurred in infants, with characteristic histologic features of a mixture of various mesenchymal tissues. McDermott et al designated it nasal chondromesenchymal hamartoma in 1998, and it has since been considered a distinct clinicopathological entity. We report 2 such examples in a full-term male newborn and a 9-month-old boy, respectively. Histologically, both cases were characterized by a mixture of various mesenchymal elements, including spindle cells, collagen fibers, and irregular islands of osseous and chondroid tissue. Immunohistochemical study showed positivity to vimentin and S100 protein. Ultrastructural examination of case 1 demonstrated fibroblastic and myofibroblastic differentiation in tumor cells. There were 11 cases of nasal chondromesenchymal hamartoma in children published to date. The tumor has a benign biological behavior, and complete resection is the treatment of choice. It is apt to be misdiagnosed because of overlapping histologic features shared with a number of benign and malignant soft tissue tumors. Awareness of this entity is essential for correct diagnosis and adequate therapy.

Giant cell angioblastoma: three additional occurrences of a distinct pathologic entity.

Giant cell angioblastoma was described previously in a single case report as a congenital soft-tissue tumor with a unique morphology. In the current report, we describe three cases of giant cell angioblastoma found in three infants; one case was congenital and located in the hand, one appeared neonatally in the palate, and one on the scalp of an infant. Clinical findings and results of light microscopy, immunohistochemistry, and electron microscopy were evaluated. All tumors were ulcerated; the hand and palate tumors also infiltrated soft tissue and bone. They exhibited a solid, nodular, and plexiform proliferation of oval-to-spindle cells with a frequent striking, concentric aggregation around small vascular channels. These cells had characteristics of undifferentiated mesenchymal cells, fibroblasts, myofibroblasts, and pericytes. Co-mingled with these cells were large mononuclear and multinucleate giant cells with histiocytic features. The palatal giant cell angioblastoma, excised with positive margins, was managed with interferon-alpha and showed no progression after nearly 5 years. The hand tumor diminished in size after management with interferon-alpha, was subtotally excised, and did not progress after 27 months. Follow-up data are unavailable for the patient with the scalp lesion. Our findings validate the classification of giant cell angioblastoma as a distinct and rare entity that is locally infiltrative but slow growing. The morphology and diverse cellular differentiation are consistent with an unusual form of neoplastic angiogenesis.

Bizarre parosteal osteochondromatous proliferation: case report and review of the literature.

Bizarre parosteal osteochondromatous proliferation of bone (BPOP) is a benign lesion that is occasionally misinterpreted as a malignant process. The original reports described lesions exclusively in the hands and feet. However, subsequent reports have included additional sites in the long bones, skull, and maxilla. The differential diagnosis of BPOP includes numerous benign and malignant lesions. The benign differential diagnosis includes osteochondroma and reactive processes. The most important malignant differential diagnosis is parosteal osteosarcoma. We present a case of an 11-year-old boy with recurrent BPOP and review the literature. We discuss the differential diagnosis and pathogenesis of the lesion.

Fibrous tumors in children - a morphologic and interphase cytogenetic analysis of problematic cases.

We describe and discuss the findings by fluorescent in situ hybridization (FISH) for detection of non-random chromosomal gains, in a group of unusual fibrous lesions in children. Nuclear disaggregation was used to prepare slides from eight cases which were hybridized using alpha-satellite enumeration probes for chromosomes 8, 11 and 17. Trisomy 8 and 11 were detected in a high percentage of nuclei in cases of congenital/infantile fibrosarcomas (ranging from 45 to 80%), and in a low grade fibrosarcoma in an older child (23%). Only gains of chromosome 17 were detected in a case of infantile fibromatosis (22%). In this study we have found that given the unconventional histopathologic features, the detection of more than one non-random chromosomal gains by FISH, may aid in further defining fibrous tumors in children, and may be useful as an ancillary diagnostic test in the future.

Calcifying fibrous pseudotumor involving the neck of a five-week-old infant. Presence of factor XIIIa in the lesional cells.

Calcifying fibrous pseudotumor is an uncommon lesion characterized by hyalinized collagen, psammomatous or dystrophic calcifications, and a predominantly lymphoplasmacytic infiltrate. Although the pathogenesis is unclear, a possible relationship with other inflammatory "pseudotumors" has been proposed. We describe the pathology of two right neck calcifying fibrous pseudotumors present in a five-week-old female infant. The masses had many of the pathologic features of calcifying fibrous pseudotumor. The presence of a florid, mixed infiltrate, and the occurrence of more than one lesion in the same patient, favor the proposal that calcifying fibrous pseudotumor may be a sclerosing end stage of inflammatory myofibroblastic tumor. However, the presence of a previously undescribed participation of Factor XIIIa-positive cells suggests that the tumor may be of dermal dendrocyte origin.

Prostanoids mediate the protective effect of trefoil factor 3 in oxidant-induced intestinal epithelial cell injury: role of cyclooxygenase-2.

Trefoil factors are small peptides found in several mammalian tissues including gut, respiratory tract and brain. Their physiological function is not well understood. Among them, trefoil factor 3 (intestinal trefoil factor) is known to be cytoprotective in the gut. However, the molecular mechanism and secondary mediators of trefoil factor 3 action are not known. In the present study, we examined whether the cyclooxygenase pathway is involved in trefoil factor 3 action. We showed that trefoil factor 3 significantly induces the production of prostaglandin E(2) and prostaglandin I(2) in IEC-18 cells (an intestinal epithelial cell line) in a dose dependent manner. Western blot and immunohistochemistry revealed that trefoil factor 3 (2.5 microM) up-regulates the expression of cyclooxygenase-2 but not cyclooxygenase-1 in IEC-18 cells. Treating cells with trefoil factor 3 (10 microM) significantly attenuated reactive oxygen species-induced IEC-18 cell injury. This effect is blocked by NS-398 (10 microM), a selective cyclooxygenase-2 inhibitor. Moreover, we demonstrated that exogenously administered carbacyclin (1 microM, a stable analogue of prostaglandin I(2)) and/or prostaglandin E(2) (1 microM) caused a significant reduction of reactive oxygen species-induced cell injury, mimicking the effect of trefoil factor 3. In summary, our results indicate that trefoil factor 3 activates cyclooxygenase-2 in intestinal epithelium to produce prostaglandin I(2) and prostaglandin E(2), which function as survival factors and mediate the cytoprotective action of trefoil factor 3 against oxidant injury.

Platelet-activating factor receptor mRNA is localized in eosinophils and epithelial cells in rat small intestine: regulation by dexamethasone and gut flora.

Platelet-activating factor (PAF) is a potent mediator involved in bowel injury. We investigated PAF receptor transcription and its mRNA localization in the small intestine of normal (conventionally fed) and germ-free rats, by competitive polymerase chain reaction (PCR) and in situ hybridization. A dose of PAF (1.5 microg/kg, i.v.) insufficient to cause gross bowel injury was injected into rats. Some rats were pretreated with dexamethasone (1 mg/kg). We found: (1) PAF receptor (PAF-R) mRNA localized predominantly in lamina propria eosinophils and in epithelial cells; (2) PAF increased PAF-receptor signals in the epithelial cells; (3) Dexamethasone depleted eosinophils in the intestine and markedly decreased PAF-receptor transcripts; the response to PAF was also weaker than control rats; (4) Germ-free rats had less PAF-R mRNA than normal rats, and showed a weaker response to PAF than conventionally fed rats. Thus, we conclude: (1) PAF receptor mRNA is constitutively expressed in the epithelium and in lamina propria eosinophils in the intestine. (2) PAF-R transcription is up-regulated by PAF and gut flora, mostly in the epithelium. (3) PAF-R transcription is down-regulated by glucocorticoids, mainly as a result of eosinophil depletion. These results suggest a functional role for PAF receptors both in host defence and the inflammatory response in the small intestine.

Indeterminate-cell histiocytosis: immunophenotypic and cytogenetic findings in an infant.

BACKGROUND: The authors report the immunohistochemical, ultrastructural, and cytogenetic findings in a case of malignant histiocytic proliferation in an infant. PROCEDURE: The patient presented initially with bone lesions without skin or systemic involvement. Multiple biopsies were studied extensively by immunohistochemistry and electron microscopy. Cytogenetic studies of cell cultures supplemented with granulocyte-monocyte colony stimulating factor (GM-CSF) were also performed. RESULTS: Morphologically, the cells resembled Langerhans cells, although with greater pleomorphism, as evinced by cells with usual polylobated nuclei. These cells expressed markers for macrophages and antigen presenting cells and were CD1a- and S-100-positive, but lacked Birbeck granules. The cells grown in culture supplemented with GM-CSF showed a unique combination of numerical and structural abnormalities affecting chromosomes 1, 6, 8, and 10. The disease followed a malignant course leading to the patient's demise despite aggressive chemotherapy and bone marrow transplant. CONCLUSIONS: The findings suggest a malignant hematopoietic stem-cell neoplasm with a capacity for macrophage or dendritic-cell differentiation. Morphology and immunophenotypic features place this neoplasm within the group recently conceptualized as indeterminate-cell histiocytosis.

Intestinal trefoil factor binds to intestinal epithelial cells and induces nitric oxide production: priming and enhancing effects of mucin.

Intestinal trefoil factor (ITF or TFF3), NO and epithelium-associated mucin have important roles in sustaining mucosal integrity in the gastrointestinal tract. In the present study we examined ITF-binding molecules on IEC-18 cells (an intestinal epithelial cell line) with the use of flow cytometry and localized these molecules on the cell surface by confocal microscopy. Furthermore, we studied the interaction of mucin and ITF and their co-operative effect on NO production by the epithelium. Stimulation of cells with mucin (5 mg/ml) for 90 min resulted in a 5-fold increase in ITF binding. Treatment of IEC-18 cells with actinomycin D or cycloheximide attenuated mucin-enhanced ITF binding. Ligand blot analysis confirmed the induction of ITF-binding protein in IEC-18 cells by mucin. These results indicate that transcriptional and translational mechanisms are involved in the effect of mucin. Treatment with ITF overnight resulted in a low level of nitrite production by the cells, a 5-fold increase over control, in a concentration-dependent manner. ITF-induced NO production was attenuated by 1400W, a selective type II nitric oxide synthase (NOS2) inhibitor. By immunoblotting we found that NOS2 was up-regulated by ITF treatment. Priming IEC-18 cells with mucin for 90 min enhanced the effect of ITF on NO production, suggesting that the up-regulation of ITF-binding molecules by mucin might be physiologically relevant. Taken together, these observations indicate (1) that ITF-binding molecules that are up-regulated by mucin exist on the intestinal epithelial surface, and (2) that ITF modulates epithelial NO production via the NOS2 pathway, which is enhanced by mucin.

Rapid growth of cutaneous metastases after surgical resection of thrombospondin-secreting small blue round cell tumor of childhood.

In animal models, the importance of tumor-derived antiangiogenic factors in controlling metastases has been demonstrated by the growth acceleration of distant metastases after surgical excision of a primary tumor mass. We report the case of an infant who developed rapidly growing cutaneous metastases after surgical resection of a neoplasm of an upper extremity. The tumor was undifferentiated, with some morphological features of primitive neuroectodermal tumor. To test the possibility that the primary tumor was secreting an angiogenic inhibitor, cells from the primary tumor were grown in culture, and the culture medium was tested with an in vitro endothelial cell migration assay and Western blot. The cultured cells secreted sufficiently high levels of an angiogenic inhibitor to overcome the inducing ability of vascular endothelial growth factor and basic fibroblast growth factor. One of the secreted proteins was thrombospondin-1, a potent antiangiogenic glycoprotein. The rapid dissemination of distant metastases after resection of the primary tumor in this case suggests that tumor-derived angiogenic inhibitors are important in maintaining the local net balance of angiogenic mediators controlling the growth of micrometastasis.

Tracheal neoplasms in children.

Primary tracheal neoplasms are extremely rare lesions in the pediatric age group. This study reviews the English-language literature to better characterize these lesions in children and reports 2 additional patients. Reports of only 36 infants and children through adolescence with primary tracheal neoplasms were discovered after an exhaustive literature review of the last 30 years. The data are analyzed with regard to pathology, demographics, symptomatology, site, and percent luminal obstruction. We report 2 additional patients with photographic documentation, imaging studies, and histopathology. Of the 36 previously reported lesions, 64% were characterized as benign and 36% as malignant. Fifty-six percent of all lesions were initially misdiagnosed as asthma. The most common site was the posterior membranous wall of the cervical trachea. In 14 (39%) of the 36 patients, the lesions obstructed more than 50% of the lumen at the time of diagnosis. The timely diagnosis of tracheal masses depends upon maintaining a high index of suspicion and conducting an efficient workup, including definitive evaluation by bronchoscopy. The evaluation and the differential diagnosis of tracheal neoplasms in the pediatric population is discussed.

Hemangiopericytoma of the liver: immunohistochemical observations, expression of angiogenic factors, and review of the literature.

PURPOSE: We describe an unusual case of a hemangiopericytoma in the liver of a child, review the literature, and characterize the tumor by immunohistochemistry and electron microscopy. We study the expression of basic fibroblast growth factor (bFGF) and of vascular endothelial growth factor (VEGF) in the tumor. MATERIALS AND METHODS: Clinical history and pathology were reviewed; sections of the tumor were studied by histology, electron microscopy, and immunohistochemistry using antibodies directed towards factor-XIIIa, HAM-56, bFGF and VEGF, among others. RESULTS: The expression of VEGF resembled that of "proliferating" hemangiomas; however, despite being markedly elevated in the urine, bFGF could not be unequivocally detected in the tumor. A subpopulation of factor XIIIa positive cells was identified, similar to the "interstitial" cells of the cellular hemangiomas of infancy. The nature and function of these cells remains speculative. CONCLUSIONS: Hemangiopericytomas are rare in the liver. When arising in this location in a child, they may clinically resemble a hemangioma, may express angiogenic factors in a similar fashion, and should be considered in the differential diagnosis.

Histopathologic changes after pericardial patch tracheoplasty.

Pericardial patch tracheoplasty has been used for surgical correction of long-segment congenital tracheal stenosis caused by complete tracheal rings in infants. The case histories of 2 infants with descriptions of the histopathologic changes in their respective tracheas are presented. Complete reepithelialization of the graft site with ciliated pseudostratified columnar epithelium was found, suggesting the likelihood of normal mucociliary flow in the trachea. The pericardial patches were replaced by mature scar tissue in the graft site, establishing a functional tracheal lumen. Wound healing in the trachea is reviewed. Obstruction by exuberant granulation tissue is an ongoing concern. Pericardium continues to be an important option as graft material for tracheal reconstruction in infants with long-segment congenital tracheal stenosis.