Malignant rhabdoid tumor is a highly aggressive pediatric neoplasm molecularly characterized by inactivating mutations of the SMARCB1 gene, a potent tumor suppressor and member of the SWI/SNF chromatin remodeling complex. It has been suggested that oncogenesis in SMARCB1-deficient cancers, such as malignant rhabdoid tumors, is driven not by the loss of SWI/SNF function but by an aberrant functioning of the BRG1-containing SWI/SNF complex. Since Brg1 is required for self-renewal and pluripotency of mouse embryonic stem cells, we hypothesized that the human malignant rhabdoid tumors may express pluripotency genes such as SALL4 , LIN28 , OCT3 and OCT4 (OCT3/4) , NANOG , and TCL1 . To test this hypothesis, we studied the immunohistochemical expression of SALL4, LIN28, OCT3/4, NANOG, and TCL1 in 11 malignant rhabdoid tumors of the central nervous system (atypical teratoid/rhabdoid tumors) and 5 malignant rhabdoid tumors of the kidney. Of the 16 malignant rhabdoid tumors, 14 (88%) tumors showed robust SALL4 and/or LIN28 expression. No tumor showed any significant OCT3/4, NANOG, or TCL1 expression. Our results suggest that malignant rhabdoid tumors may arise from and/or share features with embryonic stem cells or germ cells.

This paper reports the clinical and metabolic findings in two sibling sisters born with fetal hydrops and eventually found to have deficient S-adenosylhomocysteine hydrolase (AHCY) activity due to compound heterozygosity for two novel mutations, c.145C>T; p.Arg49Cys and c.257A>G; p.Asp86Gly. Clinically, the major abnormalities in addition to fetal hydrops (very likely due to impaired synthetic liver function) were severe hypotonia/myopathy, feeding problems, and respiratory failure. Metabolic abnormalities included elevated plasma S-adenosylhomocysteine, S-adenosylmethionine, and methionine, with hypoalbuminemia, coagulopathies, and serum transaminase elevation. The older sister died at age 25 days, but the definitive diagnosis was made only retrospectively. The underlying genetic abnormality was diagnosed in the second sister, but treatment by means of dietary methionine restriction and supplementation with phosphatidylcholine and creatine did not prevent her death at age 122 days. These cases extend the experience with AHCY deficiency in humans, based until now on only the four patients previously identified, and suggest that the deficiency in question may be a cause of fetal hydrops and developmental abnormalities of the brain.

BRAF and KRAS are two key oncogenes in the RAS/RAF/MEK/MAP-kinase signaling pathway.While previously considered mutually exclusive, concomitant mutations in both KRAS and BRAF genes have been identified in colorectal cancer (CRC). The clinical outcome of these patients remains undetermined.We present the clinical course of two patients with CRC harboring mutations at codon 12 of KRAS and BRAF non-V600E mutations. More research is needed to determine the clinical-pathological effect of these simultaneous mutations of KRAS and BRAF in CRC on disease course and treatment outcome.

Juvenile xanthogranulomas (JXG) are uncommon non-Langerhans cell histiocytic proliferations which arise most often in children. While most cases present as solitary cutaneous lesions, occasional cases involve extracutaneous sites. Rare examples of JXGs have been reported involving all levels of the neuroaxis. We present two cases of JXGs involving the nervous system, and review the literature. The first patient was a 14-year-old female with headaches and a mass involving the left trigeminal nerve; pathologic examination showed a JXG. At 11 months follow-up, after administration of systemic chemotherapy, the patient remained stable with residual tumor. The second patient was a 15-year-old female with leg weakness and numbness, who underwent complete surgical resection of a dural JXG. At eight months follow-up, she showed no evidence of tumor, and was able to walk without difficulty. Review of the literature revealed 38 previously published reports of JXGs involving the nervous system. The CNS was involved in the majority (75%) of cases. The clinical characteristics of JXGs arising in the CNS varied significantly from cases in the peripheral nervous system (PNS); CNS tumors occurred in younger patients, more often males, and were more likely to be associated with concurrent cutaneous and extra-nervous systemic lesions. The clinical outcomes were similar for CNS and PNS lesions, with the caveat that all three lethal JXGs occurred in the CNS. The clinical and radiologic presentation of JXGs is nonspecific, thus necessitating biopsy and pathologic examination to arrive at the diagnosis. The pathologic differential diagnosis includes a heterogeneous group of histiocytic proliferations; immunostaining for histiocytic markers CD68, factor XIIIa, and Fascin, and the absence of Birbeck granules and CD1a immunoexpression suggests the diagnosis of JXG. In many cases, total surgical resection is curative. However, some cases will require additional chemotherapy and/or radiotherapy.

SALL4 is a zinc finger transcription factor that plays a role in the maintainance and pluripotency of embryonic stem cell and is important in renal development where SALL4 mutations give rise to renal malformations. Because Wilms tumor recapitulates renal embryogenesis, we hypothesized that Wilms tumor cells may also express SALL4. We performed immunohistochemistry for SALL4 on tissue microarray sections of Wilms tumors, nephrogenic rests, and fetal renal cortices. Half (26 out of 52) of the Wilms tumors showed SALL4 immunoreactivity, ranging from strong and diffuse to focal and weak. Blastemal, epithelial, and combined blastemal and epithelial patterns of immunoreactivity were identified. No cases showed stromal staining. In the fetal kidney, SALL4 expression was restricted to the blastema and primitive epithelium at 15 weeks' gestation. SALL4 staining was not seen at later gestational ages, in non-neoplastic postnatal kidneys, or in nephrogenic rests. Our study is the first to demonstrate SALL4 immunoreactivity in Wilms tumors and in developing fetal kidney. The absence of SALL4 staining in nephrogenic rests, the presumed precursors of Wilms tumors, is intriguing and suggests that Wilms tumors have a pluripotency quality that may be lacking in nephrogenic rests.