Malignant neuroectodermal tumor with melanocytic and rhabdomyoblastic differentiation

Malignant melanoma can metastasize widely and vary significantly in its histological appearance; it rarely presents as a deep-seated mass without an obvious primary site elsewhere. Malignant peripheral nerve sheath tumor (MPNST) is a high-grade sarcoma characterized by conventional and epithelioid subtypes. MPNST can demonstrate heterologous differentiation, usually in the form of osteosarcomatous, chondrosarcomatous, or rhabdomyosarcomatous differentiation. MPNST does not harbor true melanocytic differentiation, although epithelioid MPNST typically is diffusely S-100 protein positive and superficially can resemble malignant melanoma. An unusual intra-abdominal mass was recently encountered with features of both melanoma and conventional or epithelioid MPNST containing a fascicular spindle cell component, an epithelioid component with melanocytic differentiation, as well as a rhabdomyosarcomatous component. The terminology “malignant neuroectodermal tumor with melanocytic and rhabdomyoblastic differentiation” is proposed to describe this neoplasm, reflecting the unusual concomittant lines of differentiation as well as offering a possible rationale for nosologically challenging aspects of this neoplasm

CDKs in Sarcoma: Mediators of Disease and Emerging Therapeutic Targets

Sarcomas represent one of the most challenging tumor types to treat due to their diverse nature and our incomplete understanding of their underlying biology. Recent work suggests cyclin-dependent kinase (CDK) pathway activation is a powerful driver of sarcomagenesis. CDK proteins participate in numerous cellular processes required for normal cell function, but their dysregulation is a hallmark of many pathologies including cancer. The contributions and significance of aberrant CDK activity to sarcoma development, however, is only partly understood. Here, we describe what is known about CDK-related alterations in the most common subtypes of sarcoma and highlight areas that warrant further investigation. As disruptions in CDK pathways appear in most, if not all, subtypes of sarcoma, we discuss the history and value of pharmacologically targeting CDKs to combat these tumors. The goals of this review are to (1) assess the prevalence and importance of CDK pathway alterations in sarcomas, (2) highlight the gap in knowledge for certain CDKs in these tumors, and (3) provide insight into studies focused on CDK inhibition for sarcoma treatment. Overall, growing evidence demonstrates a crucial role for activated CDKs in sarcoma development and as important targets for sarcoma therapy

Utility of FISH in the diagnosis of angiomatoid fibrous histiocytoma: a series of 18 cases

Angiomatoid fibrous histiocytoma is a mesenchymal neoplasm of intermediate malignancy and uncertain histogenesis/line of differentiation, which occurs most commonly in the extremities of children to young adults. It has a characteristic appearance characterized by a proliferation of histiocytoid cells with a lymphoid cuff and fibrous pseudocapsule, simulating the appearance of a neoplasm occurring within a lymph node. However, these classic histological features are not always present. Given the variable appearance of the neoplastic cells and the lack of consistently positive immunohistochemical markers, diagnosis can be problematic. Angiomatoid fibrous histiocytoma has been found to harbor three related translocations, a t(12;16)(q13;p11) resulting in a FUS/ATF1 fusion gene, t(12;22)(q13;q12) resulting in a EWSR1/ATF1 fusion, and t(2;22)(q33;q12) resulting in a EWSR1/CREB1 fusion. Fluorescence in situ hybridization ( FISH) probes to EWSR1 and FUS, in theory, should detect all three translocations/gene fusions. We evaluated 18 cases of angiomatoid fibrous histiocytoma for rearrangements of EWSR1 and FUS by FISH, the largest series to date. We found that 13 of 17 (76%) cases of angiomatoid fibrous histiocytoma harbored rearrangements of EWSR1; rearrangements of FUS were not detected in any of the cases. This study affirms that the rearrangement of EWSR1 is a common genetic event in angiomatoid fibrous histiocytoma, and is thus useful diagnostically. This study supports the fact that the rearrangement of FUS is present in only a small minority of angiomatoid fibrous histiocytomas. Interestingly, 24% of the cases were translocation negative, and did not contain rearrangements of EWSR1 or FUS by FISH. Although it is possible that these cases contained cryptic rearrangements of EWSR1 or FUS that were not detectable by our FISH probes, it also raises the possibility that another translocation/gene fusion may be present in angiomatoid fibrous histiocytoma. Finally, we discuss some of the potential pitfalls of this technique, including confusion with other mesenchymal neoplasms containing rearrangement of EWSR1, in particular Ewing's sarcoma/PNET. Modern Pathology ( 2010) 23, 93-97; doi: 10.1038/modpathol.2009.138; published online 2 October 200

<i>Trp53/Pten</i> mice injected with Ad CMV-Cre demonstrate a longitudinal increase in BLI signal.

<p>A) BLI of <i>Trp53/Pten</i> mice injected either SQ or IM with Ad CMV-Cre. Mice were injected with intraperitoneal D-luciferin and imaged using an Ami X imager. Shown are representative images of five mice from each cohort at 1 week, 9 weeks, and 17 weeks post-viral injection, demonstrating a steady increase in luciferase signal over time. B) Quantified whole-body <i>in vivo</i> BLI values as measured in photons/sec/cm²/sr are shown for individual mice for each injection group (n = 9), and compared between the two injection groups C), highlighting similar luciferase expression kinetics and values between SQ- and IM-injected animals. The difference between SQ and IM injection was statistically significant for day 1 post-injection (p = 0.045), but not thereafter. From the 2way ANOVA, overall variance due to injection method was statistically significant (p = 0.0019). In comparison to the first day post-injection, all values for both injection methods were significant (p<0.0001).</p

Generation of <i>Trp53/Pten</i> mice associated with luciferase expression.

<p>A) ROSA26 Lox-stop-Lox Luciferase, Pten^fl/fl male mice were crossed with Trp53^fl/fl female mice to generate offspring with ROSA26 LSL-Luc, Pten^fl/fl, and Trp53^fl/fl. Ad with a Cre recombinase expression vector was injected either subcutaneously over the right leg/flank or intramuscularly into the right quadriceps to promote somatic recombination. Somatic expression of Cre recombinase promoted expression of luciferase and homozygous knockout of <i>Pten</i> and <i>Trp53</i>. B) PCR from DNA isolated from either a tumor of Cre injected mice (Cre+) or from the tail of a non-injected mouse (Cre-) (Ctrl is a primer only control) to assay for the presence of recombination and floxed <i>Pten</i> or <i>Trp53</i>.</p

Trp53^fl/flPten^fl/fl mice injected with Ad CMV-Cre form soft tissue tumors with 100% penetrance.

<p>A) Photographs of representative intact SQ and IM soft tissue tumors (*). B) Primary tumor dissections highlighting the superficial nature of tumors in the SQ-injected group compared to the deep, invasive tumors in the IM group, which develop within the native quadriceps muscle and adhere firmly to the surrounding femur and musculature. C) Palpable tumor latency as defined by time to earliest manual palpation of soft tissue tumor (p = 0.3201) D) Primary tumor mass and tumor volume with corresponding BLI measurements. Tumor mass (blue squares, right y-axis) measured after surgical excision and volume (red circles, left y-axis) measured by calipers are correlated with photon flux (X-axis); Spearman <i>r</i> = 0.857 and r = 0.733, respectively. Asterisk indicates one outlying tumor that was removed from the analysis.</p

IM-injected Ad CMV-Cre results in increased systemic viral spread.

<p>A) Quantified leg-only or abdomen-only BLI values are shown for individual Trp53^fl/flPten^fl/fl mice injected either SQ or IM with Ad CMV-Cre. B) Comparisons between injection cohorts demonstrate lower non-specific signal in the abdomen with SQ injection. There was no significant difference in luciferase signal between the SQ- or IM-injected legs; however, there is a significant difference between SQ and IM abdomen injections for week 1 and beyond (p<0.05). The difference in comparison to the first day post-injection was statistically significant for both SQ (p<0.002) and IM (p<0.0001) leg injections as well as IM abdominal BLI (p<0.02). No significant difference was found for SQ abdominal BLI in comparison to day 1. C) <i>Ex vivo</i> BLI images of livers from one SQ- and one IM-injected mouse, depicting multifocal low-level recombination and luciferase expression in the livers of mice with abdominal BLI signal, suggesting systemic viral spread and infection (left panels). Histological sections of liver demonstrated extramedullary hematopoiesis, noted with arrows, but no neoplasm was identified (right panel).</p

A Trp53^fl/flPten^fl/fl mouse model of undifferentiated pleomorphic sarcoma mediated by adeno-Cre injection and <i>in vivo</i> bioluminescence imaging

<div><p>Genetic mouse models of soft tissue sarcoma provide critical insights into disease pathophysiology, which are oftentimes unable to be extracted from human tumor samples or xenograft models. In this study we describe a mouse model of soft tissue sarcoma mediated by adenoviral-Cre recombinase injection into Trp53^fl/fl/Pten^fl/fl lox-stop-lox luciferase mice. Injection of adenovirus expressing Cre recombinase, either subcutaneously or intramuscularly in two experimental groups, results in viral infection and gene recombination with 100% penetrance within the first 24 hours following injection. Luciferase expression measured by real-time bioluminescence imaging increases over time, with an initial robust increase following viral injection, followed by a steady rise over the next several weeks as primary tumors develop and grow. Intramuscular injections were more commonly associated with evidence of systemic viral distribution than subcutaneous injections. All mice developed soft tissue sarcomas at the primary injection site, with histological examination identifying 93% of tumors as invasive pleomorphic sarcomas based on microscopic morphology and immunohistochemical expression of sarcoma markers. A lymphocytic infiltrate was present in 64% of the sarcomas in this immunocompetent model and 71% of tumors expressed PD-L1. This is the first report of a viral-Cre mediated <i>Trp53/Pten</i> mouse model of undifferentiated pleomorphic sarcoma. The bioluminescence imaging feature, along with high penetrance of the model and its immunological characteristics, makes it suited for pre-clinical studies of soft tissue sarcoma.</p></div