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Abstract BACKGROUND: Most cancer patients with bone metastases report significant pain and substantial impairment in their ability to function. In particular, patients with MM are susceptible to bone pain because of bone damage. Patient-reported outcomes such as a general health outcome measure and a legacy pain instrument may provide valuable information in determining the impact of this condition. The goal of this study was to provide a descriptive profile of health status for cancer patients using the EQ-5D-3L (EQ-5D), a commonly used tool to measure health utility scores. Another goal is to evaluate the predictive information provided by the Brief Pain Inventory (BPI), a self-report pain assessment tool designed to capture pain severity and interference in patients. These information may be useful in estimating the health status of patients where the EQ-5D was not administered. METHODS: Data was pooled across three denosumab registrational trials '20050136', '20050103', and '20050244'. Patients completed the EQ-5D and the BPI at baseline. Eligible patients had histologically confirmed advanced cancers, radiographic evidence of at least one bone metastasis (or lytic bone lesion from multiple myeloma), ECOG of 2 or better and adequate organ function. Using data from patients with MM (N=168), descriptive statistics were used to present summary information on health-related quality of life states and utility scores. Linear regressions were used to examine how BPI severity and interference subscale scores relate with EQ-5D utility scores. Ordinal regressions were used to evaluate how well BPI items predict EQ-5D individual items. Bonferroni adjustments were made when evaluating the relationships of BPI items to individual EQ-5D items. These analyses were repeated using data across several groups of cancer patients to determine if similar results can be obtained (breast cancer, N=2,044, prostate cancer, N=1,819 and others, N=1,509). RESULTS: About 9% of MM patients reported perfect health compared with 11% of all cancer patients. Of the 5 dimensions measured by the EQ-5D, the MM cohort rated pain (80%) the highest with moderate to extreme problems. This was followed by usual activities (68%), mobility (63%), anxiety/depression (49%), and self-care (36%). Similar order was observed across all cancer groups, but with slightly lower percentages for most items: pain (78%), usual activities (58%), mobility (55%), anxiety/depression (57%), and self-care (26%). Although pain interference subscale score explained more of the variability in the EQ-5D utility scores compared with pain severity items in the MM cohort (39% vs 31%) and for all patients (41% vs 34%), model fit was less than ideal (mean squared error=0.23 - 0.25). Hence, BPI items were fitted into individual EQ-5D items. Ordinal regression models fitting BPI items into individual EQ-5D items for the MM cohort showed good predictive power as measured by the concordance index c for mobility (86%), self-care (80%), usual activities (83%), pain (90%) and anxiety/depression (78%). For all patients, similar model fit were obtained for mobility (83%), self-care (78%), usual activities (81%), pain (90%) and anxiety/depression (72%). Further examination of the ordinal regression models across all groups showed that three BPI pain severity items, 'pain at its worst', 'average pain' and 'pain now' in addition to interference with activity and interference with work significantly predicted the EQ-5D pain item. Five interference items, activity, walking ability, work, sleep and enjoyment of life significantly predicted the EQ-5D usual activities item. Finally, 'pain now' and four interference items, relationship with others, enjoyment of life, mood, and activity significantly predicted the EQ-5D anxiety/depression item. CONCLUSIONS: Patients with MM reported several functional limitations on the EQ-5D. Majority of the patients reported moderate to extreme problems in all EQ-5D dimensions except self-care. Model fit of ordinal regression models relating BPI items with EQ-5D items are reasonable underscoring the benefit of using the BPI for planning patient care and health status evaluation. This consistency was also found across cancer groups that primarily include breast and prostate. The resultant model demonstrates the significant contribution of pain severity and interference in determining health status in this patient population. Disclosures Mendoza: Amgen Inc.: Consultancy. Shi:Amgen Inc.: Consultancy. Ma:Amgen Inc.: Employment. Zhang:Amgen Inc.: Employment. Qian:Amgen Inc.: Employment. Cleeland:Amgen Inc.: Consultancy.

Abstract Background: It is now well established that the immune modulator (IMiD) drugs thalidomide (Thal), lenalidomide (Len) and pomalidomide (Pom) bind a specific pocket in the protein, cereblon (CRBN) that is required for MM cytotoxicity after IMiD treatment. Recently, we reported 46 CRBN binding proteins which were altered by Len, two of which were the transcription factors Ikaros (IKZF1) and Aiolis (IKZF3), important regulators of B and T cell development. Others had previously reported the same finding and went further by demonstrating that following binding of IMiD drugs, CRBN accumulates and accentuates the ubiquitination and subsequent proteasomal degradation of these two binding proteins. The resulting degradation and depletion of IKZF proteins has the simultaneous effect of downregulating IRF4 and MYC leading to MM cell death while simultaneously enhancing transcription of interleukin 2 and activating the immune compartment. Methods: To further explore this phenomenon and its relationship to drug sensitivity we first created two stable MM cell lines (H929IKZF1Luc, 8226IKZF1Luc) expressing an IKZF1-luciferase (luc) fusion gene and tested for sensitivity to Len alone and in combination with dexamethasone (Dex), bortezomib (Bor) or the histone deacetylase inhibitor SAHA. Next, we constructed an adenoviral vector expressing IKZF1-luc and used this to transfect 16 MM cell lines, confirmed expression and tested sensitivity to Len by MTT (Figure 1). Results: We first examined the stable cell lines and measured luc expression after exposure to all three IMiD drugs. With all IMiD drugs luc dramatically decreased in sensitive H929 cells. IKZF1 depletion was both time and dose dependent. Using this surrogate marker cell line assay, luc is most efficiently degraded by Pom which is twice as potent as Len, but a thousand times more potent than Thal (Concentration of drug required to reduce luc expression by 50%, Pom: 4.9nM, Len: 10.2 nM, and Thal: 4,795 nM). We then tested all 16 cell lines with Len 2uM for 5 hours and show a strong correlation of IKZF-luc depletion with sensitivity. Figure 1: Luc levels 5 hours after Len treatment at 2uM. We divided the cell lines into three groups: 1) Len resistant: 8226, KMS12PE, My5, SKMM2, JJN3, FR4, H112; 2) Len intermediate response: EJM, OPM2, U266, KMS18; 3) Len sensitive: H929, MM1.S, MM1.R, KMS11, XG1; Figure 1:. Luc levels 5 hours after Len treatment at 2uM. We divided the cell lines into three groups: 1) Len resistant: 8226, KMS12PE, My5, SKMM2, JJN3, FR4, H112; 2) Len intermediate response: EJM, OPM2, U266, KMS18; 3) Len sensitive: H929, MM1.S, MM1.R, KMS11, XG1; We next performed western blots on 9 MM cell lines and demonstrate that IKZF1 levels were lowest in 3 of 5 resistant MM cell lines and normal in all 4 sensitive lines studied. The cell line (FR4) with the lowest levels of IKZF1 harbors a damaging mutation of IZKF1 as well as a translocation which upregulates IRF4, an IKZF target. Of the remaining two resistant lines one has low levels of Cereblon. In one line the mechanism of IMiD resistance could not be established. Finally, we were curious about the dichotomy of the IMiD biology which seemingly has an absolute requirement for a functional proteasome for successful IMiD cytotoxicity which is at variance with clinical reports of synergy between the IMiDs and the proteasome inhibitors (PIs) Bor and carfilzomib (Car). To explore this, we treated the 8226IKZF1Luc cell line with Len alone or in combination with increasing concentrations of Bor (6 nM) or Car (40nM) and found that both totally blocked IKZF1 fusion protein degradation promoted by Len, beginning as soon as 1 hour at 100nM Bor or after 3 hours at 40nM treatment. Conversely, in low concentration of Bor (<4nM) no IKZF1 degradation blocking was observed in the Luc assay and Bor remained lethal to the MM cells. In that light with lower levels of Bor (<3nM) even varying the sequencing of MM cell exposure to the two drug classes did not block cytotoxicity. Other MM active drug Dex or SAHA, blocking the aggresome, had no significant inhibition for Len-induced IKZF1 fusion protein degradation. Conclusion: These results validate the central role for the CRBN-IKZF-IRF4 axis proteins in IMiD response and show a strong correlation of IZKF1 expression and the ability to degrade IKZF1 with sensitivity. Our data provide interesting and perhaps disconcerting biologic data suggesting that the timing and dosing of clinical use of IMiDs and PI treatment in combination should be carefully evaluated to prevent antagonism of effect but suggest in vitro that a therapeutic window exists at which proteasome inhibitors can be active without blocking IMiD activity. Disclosures Stewart: Sanofi: Consultancy; Array BioPharma: Consultancy; Bristol Myers Squibb: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Takeda Pharmaceuticals International Co.: Research Funding.

Abstract Abstract 573 Using high throughput RNA interference screening on 6,722 druggable genes we previously identified XPO1/CRM1 as one of the 50 most vulnerable targets in Multiple Myeloma (MM)1. XPO1 knockdown proved lethal in MM cell lines, but had no effect on human embryonic kidney (293) cells or lung cancer (A549) cells, showing that XPO1 is a specific myeloma vulnerability, and that myeloma cell survival is dependent upon XPO1 expression. XPO1 encodes the protein exportin 1, a nuclear transport protein that exports tumor suppressor proteins from the nucleus, where they are active, to the cytoplasm, where they become inactive. We next analyzed XPO1 in MM via gene expression profiling (GEP). XPO1 expression is up-regulated as the disease progresses: patients with active MM have a higher level of XPO1 compared to normal plasma cells (p<0.04) and to patients with monoclonal gammopathy of undetermined significance or smoldering MM (p<0.0001). The highest levels were in human MM cell lines. TC classification revealed highest levels in t(11;14) and lowest levels in t(4;14) disease. Selective inhibitors of nuclear export (SINE) compounds have recently been developed that irreversibly inhibit XPO1/CRM1 and its nuclear export function. One such inhibitor, KPT-276, decreased the viability of all 12 MM cell lines tested in vitro, as shown by MTT assay. After 72 hours of drug treatment, a median IC50 value of approximately 175 nM (range 30–1000 nM) was observed. No synergy with other commonly used anti-MM therapeutics was observed in vitro. In contrast, the drug had little effect in 8 solid tumor cell lines with the exception of the B cell lymphoma line Ramos. KPT-276 was also consistently active in inducing apoptosis against MM primary patient samples. Using an IC80 dose of KPT-276, drug-treated samples had a reduced population of cells in S phase (8%) compared to cells treated with DMSO (21%). Using the vkappa*myc transgenic MM model, KPT-276 reduced monoclonal spikes (by a mean of 56%) in all mice treated orally with 150 mg/kg dose three times per week for 4 weeks. Furthermore, KPT-276 significantly reduced tumor growth in a xenograft MM1.S mouse model. GEP was performed in the presence or absence of drug in two different MM cell lines. Two genes of probable relevance, cell division cycle 25 homolog A (CDC25A) and Bromodomain-containing protein 4 (BRD4), were dysregulated by SINE treatment. Both are involved in cell cycle control and have been linked to MYC. RT-PCR and western blotting confirm that MYC, CDC25A and BRD4 are down-regulated, as soon as six hours, after treatment with KPT-276. KPT-276 has shown marked anticancer activities against B cell malignancies in vitro and is active and tolerated in Phase I canine studies. KPT-330, a close analog of KPT-276, is currently in Phase 1 studies in human with advanced hematological and solid tumors. Disclosures: Schmidt: Karyopharm: Research Funding. McCauley:Karyopharm Therapeutics Inc: Employment. Shacham:Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment. Stewart:Millenium: Consultancy, Honoraria, Research Funding; Onyx: Consultancy; Celgene: Consultancy.

Abstract Abstract 3968 To better understand the genetic events associated with extra-medullary multiple myeloma (MM) we completed whole exome, long-insert whole genome and RNA sequencing on a patient with t(14;16) and neck adenopathy, as well as whole genome sequencing on two additional patients with respectively: t(4;14) and plasma cell leukemia, and del 17 with chest wall mass. All patients had multi-drug resistant disease and del 13. The frequency of somatic non-synonymous single nucleotide variants (SNV) ranged from 119 to 498, including an average of 15 truncating SNV, as well an average of 75 structural variants (range 2–147). Importantly, in one patient a truncating mutation, Q99*, on one allele and minor clone point mutation, R283K, on the second allele was observed in CRBN, a gene whose expression is required for effective lenalidomide and pomalidomide anti-myeloma activity. In the same patient a non-synonymous mutation, E171K, was also observed in PSMG2, a proteasome assembly protein, and a non-synonymous mutation, G369A, in NR3C1, a glucocorticoid receptor. Subsequently we have sequenced CRBN in 27 patients and 7 cell lines and have found no further examples of mutation in CRBN but have previously reported a bi-alleleic focal deletion in the MM.1Sres cell line. Mutations in NR3C1 have not previously been described in other MM genomes. Other, potentially clinically relevant mutations in the three patients were observed in FGFR3, PRDM1, STAT5B, NRAS, KRAS, PIK3CA, NF1, ATM, NFKB2, CKS1B and ERBB4. Although the three patients did not share a unifying event, a number of mutated genes observed were shared with other published myeloma genomes including RB1, TP53, MLL3, JAG2, VAV3 and SETD2. We also looked at pathway activation across the three genomes with the most statistically mutated pathways including VEGF signaling and activation, cell adhesion and chemokines, cytoskeleton remodeling, integrins in carcinoma progression, TP53 signaling and NOTCH signaling. In conclusion, we have identified, for the first time, the presence of a mutation in CRBN in a myeloma patient as well as mutations in PSMG2 and NR3C1, likely associated with drug resistance. Disclosures: Schmidt: Karyopharm: Research Funding. Carpten:Life Technologies: Research Funding. Stewart:Millenium: Consultancy, Honoraria, Research Funding; Onyx: Consultancy; Celgene: Consultancy.

Abstract Abstract 194 Background: Immunomodulatory drugs (IMiDs) are key components of treatment for hematologic malignancies, especially multiple myeloma (MM). Recently, we demonstrated that CRBN expression is the major mediator of IMiD action operating at least in part via interferon regulatory factor 4 (IRF4), however the clinical significance of this finding remains unclear. Methods: To better understand clinical impact, we retrospectively reviewed 148 MM patients whose tumor cells were tested for CRBN expression by Gene Expression Profiling (GEP) prior to treatment with an IMiD containing therapy. Results: GEP studies show no significant differences in CRBN expression between MGUS, smoldering MM (SMM), untreated symptomatic MM and normal plasma cells. However, differences were observed between MM cell lines of varying drug sensitivity to IMiDs and between other B-cell Neoplasia (eg low grade lymphoma has higher levels). Within the genetic subtypes of MM, levels were significantly higher for hyperdiploid patients (median 1.26) as opposed to significantly lower levels for TC class D2 (median 0.76) and average for the 4p16 (median 0.97). We next screened the University of Arkansas Medical School (UAMS) GEP database of MM patients treated with combination therapies and did not find significant correlation between CRBN expression and survival in this multi-agent regimen. We then focused on patients that received only single agent IMiD therapy with low dose dexamethasone. Review of the twelve lowest expressing patients demonstrated a lack of response to IMiDs in any patient. Finally we analyzed 53 relapsed or relapsed/refractory patients treated homogeneously in a study with pomalidomide 2–4mg daily and weekly dexamethasone 40mg. CRBN levels were assessed prior to therapy initiation. Response rates varied significantly based on gene expression level. The percentage of patients that demonstrated at least a partial response was 0% for CRBN <0.81, 19% for CRBN expression of 0.81–0.90, and 33% for CBN expression >0.9. Significant differences in PFS (3.0 months vs. 8.9 months, p = 0.0006) and in OS (9.1 months vs. 27.2 months, p = 0.01) were observed when the lowest quartile of CRBN expression was compared to the top three quartiles. Values used for the cut offs are as follows: (25%: 0.889687; 50%: 1.026542, 75%: 1.211133). While this study demonstrates a positive correlation between CRBN expression and response to pomalidomide and dexamethasone, an important caveat with respect to PFS and OS is that CRBN mRNA level is primarily a reflection of the number of copies of CRBN. Since focal deletions are uncommon, this mostly reflects chromosome 3p copy number. Since trisomy 3 is common in hyperdiploid, good prognosis disease, CRBN not only is required for IMiD function but higher levels also serve as a surrogate for low risk disease. Optimal gene expression cut offs for survival were determined using the Contal and O'Quigley method. The optimal cut point for PFS was 1.18443 and for OS was 1.17816. Conclusion: In summary, this study demonstrates, for the first time, a clinical correlation between CRBN expression and response to IMiD and dexamethasone therapy. CRBN expression is also predictive of survival outcomes and when quantified prior to therapy could potentially be utilized as a predictive biomarker for response to an IMiD based treatment. Disclosures: Stewart: Celgene: Consultancy, Honoraria.

Abstract Abstract 4055 Introduction: Approximately 15% of patients (pts) with multiple myeloma (MM) exhibit a t(4;14) translocation that results in constitutive activation of the receptor tyrosine kinase (RTK) fibroblast growth factor receptor 3 (FGFR3) in the absence of ligand. This translocation has been strongly linked with a poor prognosis and short survival compared with pts without this translocation. Dovitinib (TKI258) is an RTK inhibitor that has demonstrated in vitro inhibitory activity against FGFR (including FGFR3), vascular endothelial growth factor receptor (VEGFR), and platelet-derived growth factor receptor (PDGFR), with IC50values of approximately 10 nM. Tumor growth inhibition was observed in xenograft tumor models of MM treated with dovitinib. This study was designed to evaluate the efficacy and safety of dovitinib in pts with relapsed or refractory MM that is either t(4;14) positive or negative. Patients and Methods: Adult pts who had received at least 2 prior antimyeloma regimens and who had relapsed or were refractory to their last treatment regimen were enrolled in this multicenter, open-label, 2-stage, phase 2 trial. Pts were evaluated for t(4;14) status at the baseline visit and classified according to the result into either a t(4;14)-positive or a t(4;14)-negative group. Dovitinib was administered at a dose of 500 mg/day on a 5-days-on/2-days-off schedule. Response was characterized as per the International Myeloma Working Group (IMWG) criteria. The primary endpoint was extended overall response rate as defined by the rate of pts with best overall response of complete response, very good partial response, partial response, or minor response. Secondary endpoints included safety, overall response rate, progression-free survival, and pharmacokinetics. After disease progression, pts had the option to continue treatment with the addition of low-dose dexamethasone (40 mg every 7 days) with M-protein levels at the time of progression considered as the new baseline. Results: A total of 43 pts were enrolled in this study; 26 pts were t(4;14) negative, 13 were t(4;14) positive, and 4 pts had unknown/indeterminate t(4;14) status. Median age was 63 years. Most pts (86%; n = 37) had received ≥ 3 prior lines of therapy. No objective responses were observed in either group of pts. Due to the apparent lack of efficacy, the study did not proceed to stage 2. The following observations are based on the preliminary data. In the t(4;14)-negative group, median duration of exposure to the study drug was 4.0 weeks, and 9 of the 26 pts (35%) had stable disease, 13 (50.0%) had progressive disease, and 4 (15%) were not evaluable. Due to slow enrollment and lack of efficacy among the earlier enrolled t(4;14)-positive pts, enrollment for the t(4;14)-positive group was closed prematurely. Among the 13 enrolled t(4;14)-positive pts, median duration of exposure to the study drug was 8.7 weeks. Best responses were stable disease for 8 pts (62%), disease progression for 3 pts (23%), and unknown for 2 pts (15%). Among both groups, the most common adverse events of any grade, regardless of study drug, were nausea (67%), diarrhea (58%), vomiting (51%), fatigue (47%), thrombocytopenia (33%), and anemia (28%). Most of the nonhematologic events were mild. The most common grade 3/4 adverse events were thrombocytopenia (26%) and anemia (23%). The principal reasons for discontinuation of dovitinib monotherapy were disease progression (72%) and adverse events (19%). Six pts continued on the dovitinib plus dexamethasone regimen; 1 pt is ongoing, and 5 pts discontinued due to disease progression (n = 4) and adverse events (n = 1). Conclusion: Dovitinib was found to have no or minimal single-agent activity in relapsed/refractory myeloma irrespective of t(4;14) status. Although the patient numbers are small, the rate of patients with stable disease during study treatment who may have had a clinical benefit was higher in the t(4;14)-positive group, suggesting that this subgroup may be a candidate to explore combination treatment of dovitinib with other agents, such as proteasome inhibitors. Gastrointestinal toxicity, while mostly mild, remains a challenge, and timely monitoring and supportive care during dovitinib treatment may alleviate these symptoms. Dovitinib may be a promising agent for combination therapies to improve prognosis of patients with t(4;14)-positive MM. Disclosures: Scheid: Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Reece:Millennium Pharmaceuticals: Research Funding; Otsuka: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Merck: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding. Spencer:Celgene: Honoraria; Janssen: Honoraria, Speakers Bureau; Novartis: Honoraria. Callander:Millennium Pharmaceuticals: Research Funding. Sonneveld:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Onyx: Honoraria, Research Funding. Kalimi:Novartis Pharmaceuticals: Employment. Cai:Novartis: Employment. Shi:Novartis: Employment, Equity Ownership. Scott:Novartis: Employment. Stewart:Millennium Pharmaceuticals: Consultancy, Honoraria, Research Funding; Onyx: Consultancy; Celgene: Consultancy.

Background Pancreatoblastoma (PBL) is a rare malignant pancreatic tumor seen predominantly in childhood, and its cytologic diagnosis remains challenging. Methods Twelve fine‐needle‐aspirations from 11 adults were analyzed. Results In total, 6 men and 5 women (median age, 45 years; age range, 32‐60 years) had tumors measuring a median 5.6 cm (range, 2.5‐12 cm) located in the pancreatic head (n = 7) or tail (n = 4), including 3 with familial adenomatous polyposis (FAP)/FAP‐related syndromes and 4 with metastasis at diagnosis. The median follow‐up was 39.8 months (range, 0.8‐348 months), and 5 patients died of disease. The original cytology diagnoses were: PBL (n = 2), neuroendocrine neoplasm (n = 2), poorly differentiated neuroendocrine carcinoma (n = 2), well differentiated neuroendocrine tumor (n = 1), poorly differentiated carcinoma (n = 2), “positive for malignancy” (n = 1), acinar cell carcinoma (n = 1), and epithelioid neoplasm with endocrine and acinar differentiation versus PBL (n = 1). Universal cytopathologic findings included hypercellularity; 3‐dimensional clusters; and single, monotonous, blast‐like cells that were from 1.5 to 2.0 times the size of red blood cells with high nuclear‐to‐cytoplasmic ratio, fine chromatin, small, distinct nucleoli, and a resemblance to well differentiated neuroendocrine tumor and poorly differentiated neuroendocrine carcinoma. Branching pseudopapillae (n = 7) and grooved nuclei (n = 3) raised the differential diagnosis of solid‐pseudopapillary neoplasm, but with more atypia. Uncommon features included pleomorphism (n = 4) and numerous mitoses (n = 1). Squamoid morules were seen on smears (n = 5) or cell blocks (n = 6) in 70% of patients and were characterized by epithelioid cells with elongated, streaming nuclei, fine chromatin, absent nucleoli, and positive nuclear β‐catenin (n = 6 of 8). The median Ki‐67 index was 21% (range, 2%‐70%), and neuroendocrine marker expression was common (100%), but acinar markers were variable (63%). Conclusions A combination of cytologic findings in PBL, including a predominant population of primitive blast‐like cells, subtle squamoid morules, frequent neuroendocrine and variable acinar phenotype, should facilitate accurate cytologic diagnosis and distinction from common mimics.

BackgroundHepatocellular carcinoma (HCC) rarely involves the biliary tree and may be inadvertently sampled on bile duct brushings (BDBs).MethodsThe pathology archives of 5 institutions were searched for BDBs with HCC involvement.ResultsA total of 17 BDBs from 14 patients were obtained. There was a male:female ratio of 6:1; the median age of the patients was 59.5 years (range, 22‐80 years). The median hepatic tumor size was 6.2 cm (range, 2.2‐13.0 cm). HCC risk factors included viral hepatitis (5 patients), cirrhosis (5 patients), hemochromatosis (1 patient), and alcoholic steatohepatitis (1 patient). Jaundice with elevated bilirubin, liver enzymes, and α‐fetoprotein was common. Endoscopic retrograde cholangiopancreatography demonstrated bile duct dilatation, polypoid intraductal masses (5 samples), clots/debris (2 samples), or strictures (4 samples). All BDBs had single and clustered large cells with naked atypical nuclei, granular cytoplasm, high nuclear/cytoplasmic ratios, and nuclei with prominent macronucleoli. Less common findings included clear/microvesicular cytoplasm (35%), papillae (29%), and anisonucleosis (35%). Classic HCC features (widened trabeculae [35%], endothelial wrapping [24%], multinucleation [24%], and cytoplasmic bile pigment [35%]) were uncommon. A total of 11 BDBs were diagnosed as malignant (10 with HCC and 1 with cholangiocarcinoma), 2 were diagnosed as atypical, and 1 BDB was diagnosed as negative; approximately two‐thirds were found to have polysomy on fluorescence in situ hybridization. Approximately 71% of patients died of disease at a median of 3.5 months.ConclusionsHCC may extend into the intrahepatic and/or extrahepatic biliary tree, causing masses and/or strictures that may be sampled on BDB. Although cytologically malignant, the classic features of HCC are uncommon, which can cause misdiagnosis. Cytopathologists should be mindful of this differential when evaluating BDBs, particularly when concomitant liver masses and/or HCC risk factors are present. Because of the associated high mortality and rapid rate of death, its presence should be conveyed clearly in pathology reports.