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Pleomorphic liposarcoma (PL) is an uncommon form of liposarcoma that rarely occurs in the skin and subcutis. As its behavior in this setting is incompletely characterized, we undertook a study of a series of superficial PLs, defined as those arising or based primarily in the dermis and/or subcutis without involvement of deep structures. In addition, MDM2 gene amplification, a diagnostic signature of well-differentiated/dedifferentiated liposarcoma (WDL/DL), was evaluated to address the recent observation that this gene is amplified within PL-like areas in DL. PLs were obtained from institutional and consultation files (n=29). Cases were evaluated with respect to age, sex, location (dermis, dermis and subcutis, subcutis), size, predominant pattern (pleomorphic spindled or epithelioid), extent of lipogenic differentiation, and tumor necrosis. MDM2 amplification was analyzed using FISH on formalin-fixed, paraffin-embedded material in 26 cases. Patients ranged in age from 5 to 93 years (M:F=1.4:1). Tumors were located on the extremity (n=15), trunk (n=7), and head and neck (n=7) and involved the dermis (n=4), dermis and subcutis (n=10), and subcutis (n=15). Tumor size ranged from 0.8 to 15 cm (median=2 cm). All were mitotically active high-grade sarcomas [FNCLCC grade 2 (n=23) or 3 (n=6)] with either a pleomorphic spindled (n=24) or an epithelioid pattern (n=5) with variable extent of lipogenic differentiation [25% (n=15), 25% to 50% (n=9),50% (n=5)]. Necrosis was present in 3 cases. MDM2 gene amplification was present in 3 of 26 cases. Follow-up information in 24 cases (range=1 to 192 mo; median=48 mo; mean=59 mo) revealed local recurrences (4/24) but no metastasis or death from disease. We conclude that cutaneous and subcutaneous PLs, despite their high grade, have a much more favorable outcome compared with their deep-seated counterparts, most likely attributed to their small size and superficial location. The low incidence of MDM2 gene amplification in our series indicates that most superficial PLs are unrelated to WDL/DL. PL likely evolves by way of more than 1 molecular pathway.

The clustered homeobox proteins play crucial roles in development, hematopoiesis, and leukemia, yet the targets they regulate and their mechanisms of action are poorly understood. Here, we identified the binding sites for Hoxa9 and the Hox cofactor Meis1 on a genome-wide level and profiled their associated epigenetic modifications and transcriptional targets. Hoxa9 and the Hox cofactor Meis1 cobind at hundreds of highly evolutionarily conserved sites, most of which are distant from transcription start sites. These sites show high levels of histone H3K4 monomethylation and CBP/P300 binding characteristic of enhancers. Furthermore, a subset of these sites shows enhancer activity in transient transfection assays. Many Hoxa9 and Meis1 binding sites are also bound by PU.1 and other lineage-restricted transcription factors previously implicated in establishment of myeloid enhancers. Conditional Hoxa9 activation is associated with CBP/P300 recruitment, histone acetylation, and transcriptional activation of a network of proto-oncogenes, including Erg, Flt3, Lmo2, Myb, and Sox4. Collectively, this work suggests that Hoxa9 regulates transcription by interacting with enhancers of genes important for hematopoiesis and leukemia.

Glomangiopericytoma (sinonasal-type hemangiopericytoma) is an uncommon sinonasal neoplasm with a perivascular myoid phenotype. This tumor differs from conventional soft tissue hemangiopericytoma in location, biologic behavior, and histologic features. The proposed cell of origin is a modified perivascular glomuslike myoid cell. Glomangiopericytoma is an indolent tumor that tends to arise in the sinonasal tract of older adults and has a low malignant potential with excellent prognosis after surgical resection. Histologically, this lesion is composed of a diffuse, subepithelial proliferation of bland, uniform, closely packed spindled cells growing in a variety of patterns. A distinctive vascular network composed of variably sized vascular channels, the smaller of which demonstrate perivascular hyalinization, is often present. We report the case of a 48-year-old woman with epistaxis and nasal obstruction who was diagnosed with glomangiopericytoma and discuss the histologic differential diagnosis.

Sentinel lymph node (SLN) status currently represents the single most important prognostic factor in clinically localized melanoma and is widely used in patients with melanoma at significant risk for nodal micrometastasis. Although several studies have looked at the rates and implications of inaccuracies in the histopathologic diagnosis of melanocytic lesions, accuracy in the histologic interpretation of the SLN in melanoma has not been addressed. The goal of this study was to determine the rates of discordance in the histopathologic evaluation of the SLN and the potential clinical impact on patients referred to a comprehensive melanoma center.A prospectively collected database was queried for melanoma patients who had SLN biopsies performed at outside institutions before referral to the University of Michigan Multidisciplinary Melanoma Program between 2006 and 2009. These cases were reviewed and clinical follow-up obtained.After internal review of the SLN material, 13 (8 %) of 167 cases had major discrepancies in diagnosis that impacted patient management and prognosis. The disease of five patients was subsequently downstaged and the disease of eight patients was upstaged after internal review of the SLNs and reversal in diagnoses.There appears to be a small yet significant rate of discordance in diagnosis of the SLN for melanoma after expert histopathologic review. The implications of this discordance and revision of diagnosis is substantial. Expert histopathologic review of the SLN warrants consideration to provide the most accurate prognostic information and optimal patient care.

Basal cell carcinoma (BCC) is the most common nonmelanoma skin cancer. Most BCCs are found on areas of UV-damaged skin, The study of BCCs of sun-protected regions, however, suggests a more complex pathogenesis. We present a case of BCC of the perineum in a man with no previous history of skin cancer. This is the first report of BCC in this region and one of a small body of cases arising on or near the genital and perianal regions.

The use of mouse gene targeting to study molecules important in neural development is oftentimes impaired by early embryonic lethality. In order to address later roles for such molecules, specifically in neural stem cells, we generated transgenic mice that express both the tetracycline-inducible molecule rtTA-M2 and GFP under the control of the neural precursor specific form of nestin. Developmental analysis of these mice demonstrates that GFP expression is exclusive to the neural tube. Adult expression of GFP is seen only in known areas of adult neurogenesis, namely, the subventricular zone and the dentate gyrus. When crossed with a second transgenic mouse (TetOp-Cre) that expresses the Cre recombinase under the control of the tetracycline responsive promotor, we demonstrate temporal induction of Cre in bigenic animals exposed to doxycycline. We further demonstrate the feasibility of this approach by using the ROSA-26 reporter mouse to mediate recombination in neural precursor cells.

Low-grade fibromyxoid sarcoma (LGFMS) is a rare, typically deep-seated soft tissue neoplasm with deceptively bland cytology and metastatic potential. A t(7;16)(q34;p11) translocation, yielding a FUS/CREB3L2 fusion gene, has been identified in approximately 80%-90% of deep soft tissue LGFMS. Cutaneous fibromyxoid neoplasms occur not infrequently; dermatopathologists rarely consider LGFMS in the differential diagnosis, as this lesion is uncommon in the skin. We identified a group of superficial LGFMS and a spectrum of other cutaneous fibromyxoid neoplasms and performed fluorescence in situ hybridization (FISH) to assess the frequency of FUS rearrangement. FISH for the chromosomal rearrangement of FUS (16p11), using a dual-color, break-apart probe (Abbott Molecular/Vysis, Des Plaines, IL), was performed on formalin-fixed paraffin-embedded tissue sections from superficial LGFMS (n = 6), myxomas (n = 10), and myxofibrosarcoma/myxoid malignant fibrous histiocytomas (myxoid MFH) (n = 5). One hundred nonoverlapping tumor nuclei per case were evaluated for either fused (normal) or split (translocated) signals. Of the LGFMS, 4 of 6 (67%) showed a rearrangement of FUS (range: 72%-80% positive nuclei per 100 nuclei). The other neoplasms within the differential diagnosis were devoid of any rearrangement involving FUS (range: 0%-2% positive nuclei per 100 nuclei). Our observed frequency of FUS rearrangement in superficial LGFMS is consistent with those published in the literature for more deeply seated lesions. When applied to suspicious superficial myxoid or fibromyxoid neoplasms, the FUS FISH probe in formalin-fixed paraffin-embedded tissue can be a useful ancillary technique for diagnosis of this uncommon and deceptively bland tumor.

The homeobox transcription factors Hoxa9 and Meis1 are critical mediators of transformation by MLL fusion proteins and have also been associated with poor prognosis in other AML subtypes. Despite their pivotal role in leukemia, their mechanism of cooperation and their direct target genes are largely unknown. We have established an experimental model to address these questions by transforming murine hematopoietic progenitors with epitope-tagged forms of Hoxa9 and Meis1. Chromatin immunoprecipitation and massively parallel Illumina sequencing (ChIP-seq) was used to identify binding sites for Hoxa9 and Meis1 across the genome in leukemic cells. We generated 1.7 Gb of sequence data for immunoprecipitated DNA and an untagged control, using two biological replicates, and filtered out (1) regions with nonspecific binding, (2) enriched regions that overlapped certain types of repetitive elements, and (3) nonreproducible enriched regions. We validated a subset of enriched regions by ChIP-chip and ChIP-PCR. De novo motif discovery verified that the resulting set of regions contained a motif that corresponded (E value = 6E-16) to a published Hoxa9 binding motif (Shen et al.; Mol. Cell. Biol. 1999, 19:3051–61). Overlapping or immediately adjacent binding of Hoxa9 and Meis1 was seen for 52% of Hoxa9 and 33% of Meis1 enriched regions, suggesting that these two transcription factors cooperate directly in oncogenesis rather than acting through parallel pathways. Only 7% of enriched regions fell within 2 Kb of known transcriptional start sites, while 46% of regions were within gene boundaries; the remaining peaks were intergenic. Remarkably, given the low overall level of intergenic sequence conservation, over 95% of enriched regions overlapped evolutionarily highly conserved regions (Phastcons for 17 mammalian species >50%; P value2-fold change, respectively. Phenotypic changes are evident by 96 h; therefore, the 72 h timepoint is most informative of direct Hoxa9 targets. We compared these data to genes containing ChIP-seq peaks and genes with transcription start sites closest to intergenic peaks. ~10% of genes altered at 72 h were associated with a ChIP-seq peak. Another group of investigators identified targets of Meis1 through comparison of Hoxa9- and Hoxa9+Meis1-immortalized cells (Wang et al.; Blood 2005, 106:254–63); ~14% of reported Meis1 targets were associated with a ChIP-seq peak. Hoxa9 and Meis1 binding sites in selected target genes, such the tyrosine kinase Flt3 and the surface marker Cd34, have been confirmed by ChIP-PCR/ChIP-chip. Our current data support a model in which Hoxa9 and Meis1 directly modulate a substantial number of downstream effectors through co-occupancy of regulatory motifs within proximal promoters, intragenic elements, and distally located regions. Studies are underway to determine whether Hoxa9/Meis1 binding influences gene expression and epigenetic modification at promoters and particularly at HCNEs.