Renal oncocytoma (RO) may present with a tubulocystic growth in 3% to 7% of cases, and in such cases its morphology may significantly overlap with tubulocystic renal cell carcinoma (TCRCC). We compared the morphologic and immunohistochemical characteristics of these tumors, aiming to clarify the differential diagnostic criteria, which facilitate the discrimination of RO from TCRCC. Twenty-four cystic ROs and 15 TCRCCs were selected and analyzed for: architectural growth patterns, stromal features, cytomorphology, ISUP nucleolar grade, necrosis, and mitotic activity. Immunohistochemical panel included various cytokeratins (AE1-AE3, OSCAR, CAM5.2, CK7), vimentin, CD10, CD117, AMACR, CA-IX, antimitochondrial antigen (MIA), EMA, and Ki-67. The presence of at least focal solid growth and islands of tumor cells interspersed with loose stroma, lower ISUP nucleolar grade, absence of necrosis, and absence of mitotic figures were strongly suggestive of a cystic RO. In contrast, the absence of solid and island growth patterns and presence of more compact, fibrous stroma, accompanied by higher ISUP nucleolar grade, focal necrosis, and mitotic figures were all associated with TCRCC. TCRCC marked more frequently for vimentin, CD10, AMACR, and CK7 and had a higher proliferative index by Ki-67 (>15%). CD117 was negative in 14/15 cases. One case was weakly CD117 reactive with cytoplasmic positivity. All cystic RO cases were strongly positive for CD117. The remaining markers (AE1-AE3, CAM5.2, OSCAR, CA-IX, MIA, EMA) were of limited utility. Presence of tumor cell islands and solid growth areas and the type of stroma may be major morphologic criteria in differentiating cystic RO from TCRCC. In difficult cases, or when a limited tissue precludes full morphologic assessment, immunohistochemical pattern of vimentin, CD10, CD117, AMACR, CK7, and Ki-67 could help in establishing the correct diagnosis.

Background Binding of PD-1 with ligands (e.g. PD-L1) expressed on tumor cells or native antigen-presenting cells results in down-regulation of effector T cell function and represents a potent mechanism of immune evasion across a number of solid tumors and lymphomas especially classical Hodgkin lymphoma (CHL) and aggressive virus-associated B-cell lymphomas. Several biomarkers (different antibodies, gene amplifications and mutations) are being investigated for identifying patients who may benefit from PD-1 checkpoint blockade therapies. It is well known that tumors which strongly express PD-L1 have a high clinical response rate to PD1 blockade. We aimed at identifying the expression of PD-L1 and PD1 in a diverse group of lymphomas. There are several antibodies used to detect PD-L1 expression, however the concordance between these antibodies is not known. We have previously tested concordance of 2 anti-PD-L1 antibodies in histiocytoses [1], but data in lymphomas are lacking. In the current study, we measured PD-L1 expression in lymphoma biopsy samples using 3 antibodies to identify if there was concordance in expression patterns of PD-L1 in various subtypes of lymphomas. Methods Formalin fixed paraffin embedded tissues from 37 patients with lymphomas of B- and T-cell lineages (both EBV-positive and negative) were investigated for the expression of PD-1 (MRQ-22 antibody) and PD-L1 (MAB1561, SP142 and SP263) using automated immunohistochemical methods. Expression of PD-L1 on 5% or more lymphoma cells was considered positive. Results Neoplastic cells expression of PD-L1 was identified in 13/37 cases (35% of all cases). The strongest (3+/>50% cells) and consistent (4/4 cases) expression was observed in Hodgkin RS cells of CHL (2/2 nodular sclerosis and 2/2 lymphocyte depleted). Other B-cell lineage lymphomas positive for expression of PD-L1 included diffuse large B-cell lymphomas (5/9 DLBCL) and lymphomatoid granulomatosis (1/1 LYG). Small lymphocytic lymphoma (n=3), splenic marginal zone lymphoma (n=2) and follicular lymphomas (n=8) were all negative. One of four mantle cell lymphomas (MCL) was borderline (5% of cells) positive. One NK/T-cell lymphoma was strongly (>50% cells) positive; four peripheral T-cell lymphomas (PTCL) and one T cell lymphoblastic lymphoma were negative. PD-L1 expression was observed in both EBV- positive (2/4) and negative (2/3) malignancies. Concordance between any 2 anti-PD-L1 antibodies varied between 86 and 97% (Table 1) with all 3 Abs agreeing in 82%. PD-1 was expressed on malignant cells in 3 cases (2 PTCL and 1 DLBCL); reactive PD-1+ T-lymphocytes were absent in LD CHL and variably present in all other lymphomas. Conclusions Over-expression of PD-L1was detected in classic HD, diffuse large B cell lymphoma, NK/T cell lymphoma and lymphomatoid granulomatosis. A high concordance in detection of PD-L1 between three antibodies indicates little need for companion diagnostic kits, but correlation between clinical responses and level of PDL1 and PD1 expression in lymphoma should be established in future clinical trials. | Antibodies (n) | MAB1561 | SP142 | SP263 | | -------------- | ----------- | ----------- | ----------- | | MAB1561 (23) | -- | 20/23 (86%) | | | SP142 (37) | -- | -- | 34/35 (97%) | | SP263 (35) | 19/22 (86%) | -- | -- | Table 1. Concordance between the PD-L1 antibodies. References: 1. Gatalica, Z., et al., Disseminated histiocytoses biomarkers beyond BRAFV600E: frequent expression of PD-L1. Oncotarget, 2015. Disclosures Gatalica: Caris Life Sciences: Employment. Arguello: Caris Life Sciences: Employment, Equity Ownership. Reddy: Caris Life Sciences: Employment. Ghosh: Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Malignant phyllodes tumor is a rare breast malignancy with sarcomatous overgrowth and with limited effective treatment options for recurrent and metastatic cases. Recent clinical trials indicated a potential for anti-angiogenic, anti-EGFR and immunotherapeutic approaches for patients with sarcomas, which led us to investigate these and other targetable pathways in malignant phyllodes tumor of the breast. Thirty-six malignant phyllodes tumors (including 8 metastatic tumors with two cases having matched primary and metastatic tumors) were profiled using gene sequencing, gene copy number analysis, whole genome expression, and protein expression. Whole genome expression analysis demonstrated consistent over-expression of genes involved in angiogenesis including VEGFA, Angiopoietin-2, VCAM1, PDGFRA, and PTTG1. EGFR protein overexpression was observed in 26/27 (96%) of cases with amplification of the EGFR gene in 8/24 (33%) cases. Two EGFR mutations were identified including EGFRvIII and a presumed pathogenic V774M mutation, respectively. The most common pathogenic mutations included TP53 (50%) and PIK3CA (15%). Cases with matched primary and metastatic tumors harbored identical mutations in both sites (PIK3CA/KRAS and RB1 gene mutations, respectively). Tumor expression of PD-L1 immunoregulatory protein was observed in 3/22 (14%) of cases. Overexpression of molecular biomarkers of increased angiogenesis, EGFR and immune checkpoints provides novel targeted therapy options in malignant phyllodes tumors of the breast.

Regulated cell death (RCD) is a controlled cellular process, essential for normal development, tissue integrity and homeostasis, and its dysregulation has been implicated in the pathogenesis of various conditions including developmental and immunological disorders, neurodegenerative diseases, and cancer. In this review, we briefly discuss the historical perspective and conceptual development of RCD, we overview recent classifications and some of the key players in RCD; finally we focus on current applications of RCD in diagnostic histopathology.

Aims The aim of the present study was to immunohistochemically investigate the expression and prognostic significance of putative cancer stem cell markers CD117 (c-kit), CD34, CD20 and CD15 in a cohort of patients with primary choroidal and ciliary body melanoma. Methods The immunohistochemical expression of these markers was evaluated using 3,3′-diaminobenzidine tetrahydrochloride (DAB) and 3-amino-9-ethylcarbazole (AEC) chromogens on paraffin-embedded tissue samples from 40 patients who underwent enucleation in the period from 1985 through 2000. Thirty-one patients had adequate tissue specimens for the analysis. Results CD117 overexpression was observed in 12 of the 31 samples (39%) when AEC chromogen was used and in 14 of 26 (54%) samples when DAB was used. CD15 positivity was seen in three out of 30 (10%) samples with AEC and in six out of 26 (23%) samples with DAB. CD20 and CD34 exhibited no positivity in the tested samples. During the average follow-up time of 8.7 years (range 0.5–22 years), 17 patients (55%) died due to metastatic disease. The Kaplan–Meier plots showed a significantly shorter overall and disease-free survival in CD117-positive patients when the AEC chromogen was used. CD15 expression was not associated with patients’ survival. In multivariate analysis, patients expressing the CD117 AEC had 4.13 times higher risk of lethal outcome in comparison with CD117 AEC negative patients. Conclusions Our retrospective cohort study has for the first time demonstrated a small proportion of CD15-positive uveal melanomas. CD117 AEC overexpression was associated with a worse outcome in patients with choroidal and ciliary body melanoma. Further studies should confirm the validity of these observations and their potential for targeted treatment modalities.

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.

e22207 Background: Histiocytoses are rare tumors characterized by the primary accumulation of monocytes, macrophages and dendritic cells. The most frequent subtypes are Rosai-Dorfman disease (RDD), Langerhans cell histiocytosis (LCH), Erdheim-Chester disease (ECD) and follicular dendritic cell sarcomas (FDCS). Clinical presentations range from localized to disseminated, life threatening disease. Identification of an activating BRAFV600E mutation in the majority of ECD and LCH cases provided the basis for the use of BRAF and MEK inhibitors in these patients. Responses have been reported with BRAF inhibitors, but no curative treatment has yet been developed. Thus, additional targeted therapies are needed. Methods: Twenty-two cases (M:F = 13:9, age range 2-65 years) of histiocytic diseases (4 RDD, 10 LCH, 4 ECD, 2 FDCS, 1 histiocytic sarcoma [HS] and 1 blastic plasmacytoid dendritic cell neoplasm [BPDCN]) were analyzed using immunohistochemical and molecular methods (cobas 4800 BRAFV600 Mutation Test and The...

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