The histiocytoses are rare tumors characterized by the primary accumulation and tissue infiltration of histiocytes and dendritic cells. Identification of the activating BRAFV600E mutation in Erdheim-Chester disease (ECD) and Langerhans cell histiocytosis (LCH) cases provided the basis for the treatment with BRAF and/or MEK inhibitors, but additional treatment options are needed. Twenty-four cases of neoplastic histiocytic diseases [11 extrapulmonary LCH, 4 ECD, 4 extranodal Rosai-Dorfman disease (RDD), 3 follicular dendritic cell sarcoma (FDCS), 1 histiocytic sarcoma (HS) and 1 blastic plasmacytoid dendritic cell neoplasm (BPDCN)] were analyzed using immunohistochemical and mutational analysis in search of biomarkers for targeted therapy. BRAF V600E mutations were detected in 4/11 LCH and 4/4 ECD cases. A pathogenic PTEN gene mutation and loss of PTEN protein expression were identified in the case of HS. Increased expression of PD-L1 (≥2+/≥5%) was seen in 3/4 ECD, 7/8 LCH, 3/3 FDCS and 1/1 HS, with overall 81% concordance between 2 antibodies used in the study (SP142 vs. MAB1561 clone). These results show for the first time significant expression of the PD-L1 immune checkpoint protein in these disorders, which may provide rationale for addition of immune check-point inhibitors in treatment of disseminated and/or refractory histiocytoses.

3597 Background: Approximately 15% of colorectal cancers (CRC) display high level of microsatellite instability (MSI-H) due to either hereditary predisposition (Lynch syndrome, LS) or somatic hyper...

Secondary angiosarcoma of the breast is a rare, but well-described complication of radiation therapy for primary breast carcinoma. Currently, it appears refractory to most systemic chemotherapy though rare responses to taxanes exist (1,2). Overall, patient prognosis is poor (3). A 78-year-old female underwent left breast conservation and axillary node dissection in 1999 for invasive ductal carcinoma followed by whole breast radiation therapy. Eleven years later, she noted multiple small nodules in the medial aspect of the left breast. Biopsy of the nodules revealed angiosarcoma of the breast. A metastatic follow-up showed no evidence of distant disease and a modified radical mastectomy performed. Histopathology confirmed the presence of angiosarcoma with all margins negative. The patient completed a course of postmastectomy irradiation with dose limitation by previous radiation for her original breast conserving procedure. This was administered concurrently with adjuvant chemotherapy (Taxol and Adriamycin). The patient did not tolerate the chemotherapy but finished the course of radiation therapy. Ten months later, angiosarcoma nodules recurred along the mastectomy scar. Chemotherapy with single agent carboplatinum was ineffective. Six months later, she underwent a wide resection of the skin and soft tissue of the left chest wall with multiple cutaneous nodules and positive deep margin (the pectoral muscle/ribs) was noted. In the interim, she underwent a split thickness skin graft to cover the large defect. Within 6 months, recurrent disease appeared in the graft and surrounding soft tissue. With no documented distant metastases, the patient again underwent a resection of recurrent tumors, chest wall and two ribs requiring TRAM flap coverage. A Caris profile was requested. She remained free of local recurrence for only 4 months, when multiple and rapidly growing subcutaneous nodules became evident about the chest wall and flap (Fig. 1A). The Caris gene expression assay performed earlier demonstrated a potential therapeutic benefit of sunitinib due to the upregulation of VEGFR2. Sunitinib was then

Epigenetic mechanisms play a crucial role in cellular proliferation, migration and differentiation in both normal and neoplastic development. One of the key signaling pathways whose components are altered through the epigenetic mechanisms is the Wnt signaling pathway. In this review, we briefly discuss the key concepts of epigenetics and focus on the recent advances in the Wnt signaling pathway research and its potential diagnostic and therapeutic implications.

Background Cancer of unknown primary (CUP) accounts for approximately 3% of all malignancies. Despite extensive laboratory and imaging efforts, the primary site usually cannot be unequivocally confirmed, and the treatment for the most part remains empirical. Recently, identification of common cancer pathway alterations in diverse cancer lineages has offered an opportunity to provide targeted therapies for patients with CUP, irrespective of the primary site. Patients and Methods 1806 cancers of unknown primary were identified among more than 63,000 cases profiled at Caris Life Sciences. Multiplatform profiling of the tumor samples included immunohistochemistry, gene sequencing and in situ hybridization methods in an effort to identify changes in biomarkers that are predictive of drug responses. Results Biomarkers associated with a potential drug benefit were identified in 96% of cases. Biomarkers identified included those associated with potential benefit in nearly all classes of approved cancer drugs (cytotoxic, hormonal, targeted biological drugs). Additionally, biomarkers associated with a potential lack of benefit were identified in numerous cases, which could further refine the management of patients with CUP. Conclusion Comprehensive biomarker profiling of CUP may provide additional choices in treatment of patients with these difficult to treat malignancies.

Secreted frizzled-related proteins 1 and 3 (SFRP1 and SFRP3) act as Wnt signaling pathway antagonists and play an important role in embryonic development and carcinogenesis. The aim of the present study was to analyze immunohistochemically the distribution of 2 SFRP family proteins, SFRP1 and SFRP3, in an experimental rat model, in normal and intrauterine growth-restricted (IUGR) human placentas, and in a subset of the corresponding human trophoblastic tumors (pure choriocarcinomas and mixed germ cell tumors with choriocarcinoma component). In rats, expression of both SFRP1 and SFRP3 was pronounced in the perimetrium and myometrium, whereas decidual cells showed only occasional positive cytoplasmic staining. The most prominent expression of both proteins was found in blood vessel endothelial cells. Stereological variable of volume density (Vv, mm0) showed statistically higher expression of SFRP1 and SFRP3 in human IUGR placentas than in normal pregnancy placentas (P<0.0001). Compared with adjacent normal/benign tissues, reduced expression of SFRP1 and SFRP3 was observed in human trophoblastic tumors (58.5% and 31.25%, respectively), although none of the examined tumors exhibited complete loss of either protein. Our study indicates that increased expression of both SFRP1 and SFRP3 may contribute to the pathogenesis of IUGR placental dysfunction, whereas the loss of these proteins may be involved in the development of human trophoblastic tumors.

We report two new cases of cystic fibroepithelioma of Pinkus together with immunohistochemical features and analyze the presence of cystic changes in a series of 16 classical fibroepitheliomas of Pinkus. Our findings show that the formation of cystic spaces is most probably caused by ischemic degeneration of stromal fenestrations, rather than by central tumor cell necrosis. This finding is supported by lack of CD34 positive blood vessels in edematous and hyalinized stromal fenestrations undergoing transformation into cystic spaces, as opposed to the uninvolved stromal fenestrations. Therefore, it is probably more accurate to refer to this process as pseudocystic stromal degeneration rather than true cyst formation. Also, two out of 16 classical Pinkus fibroepitheliomas exhibited focal pseudocystic changes in 50% and 10% of the tumor, respectively, demonstrating that this degenerative process can be found, rarely and focally, in classical cases as well.

ABSTRACT Aim: 5-FU based treatment remains the standard of care for the adjuvant treatment of colorectal carcinoma (CRC), in combination with oxaliplatin and irinotecan. CRC is molecularly heterogenous disease and patients with microsatellite stable (MSS) CRC have been previously shown to benefit from 5-FU based therapies while patients with high microsatellite instability (MSI-H) CRC did not. We investigated the expression thymidylate synthase, the targeted enzyme for 5-FU and topoisomerase I (Topo1), the targeted enzyme for irinotecan, in molecularly defined cohort of CRC. Methods: 106 patients with CRC (86 MSS and 20 MSI-H) were molecularly profiled using multiplatform approach [Caris Life Sciences] including immunohsitochemistry, PCR microsatellite analysis and gene sequencing (NGS) . Results: TS over-expression (over the ≥1+ and ≥10% threshold, and frequently >2+ and >50%) was observed in all 20 MSI-H cases (100%). In contrast, MSS cases overexpressed TS in only 31/86 (36%) of the cases (p Conclusions: Two most common molecular subtypes of colorectal cancer exhibit different expression patterns of TS and Topo1; overexpression of TS may explain the observed lack of benefit of 5-FU based therapy in MSI-H CRC patients. Additional genetic and molecular biomarkers could provide guidance to alternative chemotherapy modalities. Disclosure: Z. Gatalica: Stock options Caris Life Sciences; D. Bryant: Stock options Caris Life Sciences All other authors have declared no conflicts of interest.

ABSTRACT Aim: Malignant phyllodes tumors constitute 0.1% of all breast tumors, which lack effective treatment options. Comprehensive molecular profiling of rare cancers holds the promise of identifying underlying pathogenetic mechanisms with potentially druggable targets. Methods: Seventeen malignant phyllodes tumors (9 primary, 3 recurrent and 5 metastatic samples) were analyzed (Caris Life Sciences, Phoenix, AZ) using gene sequencing (NGS and Sanger), gene copy number analysis (FISH and CISH), RNA expression (RT-qPCR and whole genome microarrays) and protein expression (immunohistochemistry). Results: Malignant phyllodes tumors showed co-expression of genes involved in angiogenesis (vascular endothelial growth factor A and its receptor KDR) in 6 of 9 cases, and additional 3 cases showed overexpression of VEGFA alone. Amplification of EGFR gene was observed in 4 of 9 tested cases, while EGFR protein overexpression (H-score ≥ 20) was observed in 10 of 11 tested cases. TP53 mutations were identified in the majority of cases tested (8/11). One metastatic tumor harbored increased cMET gene copy number. No other oncogene alterations were identified (e.g. HER2, BRAF, KRAS, PIK3CA, cKIT). DNA repair pathways were altered in 9 out of 17 cases (7/17 low ERCC1; 2/17 low BRCA1) indicating potential response to platinum agents. Low expression of TS and RRM1 (9/17 cases) indicates potential response to fluoropyrimidines and gemcitabine. Steroid receptors were uniformly negative in all cases. Conclusions: Comprehensive tumor profiling identified diverse molecular alterations providing insight into potentially beneficial therapies in all malignant phyllodes tumors. These include novel therapies targeting angiogenesis and the EGFR pathway, as well as biomarkers of the conventional chemotherapy in this rare cancer type. Disclosure: Z. Gatalica: Stock options Caris Life Sciences; R. Bender: Stock options Caris Life Sciences. All other authors have declared no conflicts of interest.

ABSTRACT Aim: Angiosarcoma of the breast is a rare, aggressive soft tissue neoplasm occurring as either a primary or secondary malignancy due to previous radiotherapy for breast carcinoma. There is an unmet medical need for targeted therapies for angiosarcoma. Methods: Seventeen patients with angiosarcoma of the breast were identified (Caris Life Sciences) and profiled for biomarkers of drug response using multiplatform methodologies (Tumor DNA sequencing, gene copy number alterations, RNA/microarray and protein/IHC expression). Results: Eight primary, 5 post-radiation and 4 mammary angiosarcomas of unknown etiology were identified in women (age 31-85 years), all exhibiting multiple biomarker alterations. Eight out of 17 cases (47%) harbored overexpression (mRNA and/or protein) of the genes [VEGFR2 (5/17), PDGFRA/PDGFRB (3/17), c-KIT (2/17)] that can be targeted by multikinase inhibitor Sunitinib. Based on the VEGFR2 overexpression, one patient with recurrent, refractory angiosarcoma was treated with Sunitinib resulting in a complete remission and is disease free at 14 months. Also, multiplatform molecular profiling revealed useful predictors of various other treatment modalities including anthracyclines (overexpression of topoisomerase 2a in 69%), topo 1 inhibitors (topoisomerase 1 overexpression in 44%), and fluoropyrimidines (low levels of thymidylate synthase in 29%). One case devoid of the Sunitinib-associated genetic alterations harbored a KRAS mutation indicating a potential benefit of MEK inhibitors. Conclusions: A comprehensive molecular profiling of breast angiosarcomas enables identification of various molecular alterations that can be treated by both targeted and conventional treatment modalities. Disclosure: All authors have declared no conflicts of interest.