Nora Katabi

Follicular Variant of Papillary Thyroid Carcinoma A Clinicopathologic Study of a Problematic Entity

There is continuous debate regarding the optimal classification, prognosis, and treatment of the follicular variant of papillary thyroid carcinoma (FVPTC). The objective of this study was to assess the behavior of FVPTC, especially its encapsulated form, and shed more light on its true position in the classification scheme of well differentiated thyroid carcinoma.

EWSR1‐POU5F1 fusion in soft tissue myoepithelial tumors. A molecular analysis of sixty‐six cases, including soft tissue, bone, and visceral lesions, showing common involvement of the EWSR1 gene

The diagnosis of myoepithelial (ME) tumors outside salivary glands remains challenging, especially in unusual clinical presentations, such as bone or visceral locations. A few reports have indicated EWSR1 gene rearrangement in soft tissue ME tumors, and, in one case each, the fusion partner was identified as either PBX1 or ZNF444. However, larger studies to investigate whether these genetic abnormalities are recurrent or restricted to tumors in soft tissue locations are lacking. Sixty‐six ME tumors mainly from soft tissue (71%), but also from skin, bone, and visceral locations, characterized by classic morphological features and supporting immunoprofile were studied. Gene rearrangements in EWSR1, FUS, PBX1, and ZNF444 were investigated by fluorescence in situ hybridization. EWSR1 gene rearrangement was detected in 45% of the cases. A EWSR1‐POU5F1 fusion was identified in a pediatric soft tissue tumor by 3′Rapid Amplification of cDNA Euds (RACE) and subsequently confirmed in four additional soft tissue tumors in children and young adults. An EWSR1‐PBX1 fusion was seen in five cases, whereas EWSR1‐ZNF444 and FUS gene rearrangement was noted in one pulmonary tumor each. In conclusion, EWSR1 gene rearrangement is a common event in ME tumors arising outside salivary glands, irrespective of anatomical location. EWSR1‐negative tumors were more often benign, superficially located, and showed ductal differentiation, suggesting the possibility of genetically distinct groups. A subset of soft tissue ME tumors with clear cell morphology harbor an EWSR1‐POU5F1 fusion, which can be used as a molecular diagnostic test in difficult cases. These findings do not support a pathogenetic relationship between soft tissue ME tumors and their salivary gland counterparts.

The mutational landscape of adenoid cystic carcinoma

Adenoid cystic carcinomas (ACCs) are among the most enigmatic of human malignancies. These aggressive salivary gland cancers frequently recur and metastasize despite definitive treatment, with no known effective chemotherapy regimen. Here we determined the ACC mutational landscape and report the exome or whole-genome sequences of 60 ACC tumor-normal pairs. These analyses identified a low exonic somatic mutation rate (0.31 non-silent events per megabase) and wide mutational diversity. Notably, we found mutations in genes encoding chromatin-state regulators, such as SMARCA2, CREBBP and KDM6A, suggesting that there is aberrant epigenetic regulation in ACC oncogenesis. Mutations in genes central to the DNA damage response and protein kinase A signaling also implicate these processes. We observed MYB-NFIB translocations and somatic mutations in MYB-associated genes, solidifying the role of these aberrations as critical events in ACC. Lastly, we identified recurrent mutations in the FGF-IGF-PI3K pathway (30% of tumors) that might represent new avenues for therapy. Collectively, our observations establish a molecular foundation for understanding and exploring new treatments for ACC.

EWSR1‐ATF1 fusion is a novel and consistent finding in hyalinizing clear‐cell carcinoma of salivary gland

Hyalinizing clear‐cell carcinoma (HCCC) is a rare, low‐grade salivary gland tumor with distinctive clear‐cell morphology and pattern of hyalinization as well as focal mucinous differentiation. However, histological overlap exists with other salivary gland tumors, such as epithelial–myoepithelial carcinoma (EMCa), salivary myoepithelial carcinoma, and mucoepidermoid carcinoma (MEC). The potential relationship between HCCC and its morphological mimics has not been yet investigated at the genetic level. In this study, we conducted a molecular analysis for the presence of rearrangements in MAML2, commonly seen in MECs, and EWSR1, involved in “soft tissue myoepithelial tumors” (SMET) by fusion with POU5F1, PBX1, or ZNF444. Fluorescence in situ hybridization (FISH) was performed on 23 HCCC cases for abnormalities in MAML2, EWSR1, FUS, POU5F1, PBX1, and ZNF444. FISH for MAML2 was negative in all cases (0 of 14), including those with mucinous differentiation (0 of 7). An EWSR1 rearrangement was identified in 18 of 22 HCCCs (82%), while no break‐apart signals were seen in FUS, POU5F1, PBX1, or ZNF444. 3′RACE on an EWSR1 rearranged HCCC identified an EWSR1‐ATF1 fusion, which was confirmed by RT‐PCR. ATF1 involvement was further confirmed by FISH analysis in 13 of 14 EWSR1‐rearranged HCCC cases (93%). In contrast, all control cases tested, including among others 5 EMCa and 3 MEC with clear cells, were negative for EWSR1 and ATF1 rearrangements. The presence of EWSR1‐ATF1 fusion in most HCCCs reliably separates these tumors from its histological mimics. The distinction from MEC is particularly important, as conventional MEC grading schemes overgrade these indolent HCCCs, potentially impacting on treatment.

Intraductal papillary neoplasm of the bile duct: A biliary equivalent to intraductal papillary mucinous neoplasm of the pancreas?

Intraductal papillary neoplasm of the bile duct (IPNB) is a variant of bile duct carcinoma characterized by intraductal growth and better outcome compared with the more common nodular‐sclerosing type. IPNB is a recognized precursor of invasive carcinoma, but its pathogenesis and natural history are ill‐defined. This study examines the clinicopathologic features and outcomes of IPNB. A consecutive cohort of patients with bile duct cancer (hilar, intrahepatic, or distal) was reviewed, and those with papillary histologic features identified. Histopathologic findings and immunohistochemical staining for tumor markers and for cytokeratin and mucin proteins were used to classify IPNB into subtypes. Survival data were analyzed and correlated with clinical and pathologic parameters. Thirty‐nine IPNBs were identified in hilar (23/144), intrahepatic (4/86), and distal (12/113) bile duct specimens between 1991 and 2010. Histopathologic examination revealed 27 pancreatobiliary, four gastric, two intestinal, and six oncocytic subtypes; results of cytokeratin and mucin staining were similar to those of intraductal papillary mucinous neoplasm (IPMN) of the pancreas. Invasive carcinoma was seen in 29/39 (74%) IPNBs. Overall median survival was 62 months and was not different between IPNB locations or subtypes. Factors associated with a worse median survival included presence and depth of tumor invasion, margin‐positive resection, and expression of MUC1 and CEA. Conclusion: IPNBs are an uncommon variant of bile duct cancer, representing approximately 10% of all resectable cases. They occur throughout the biliary tract, share some histologic and clinical features with IPMNs of the pancreas, and may represent a carcinogenesis pathway different from that of conventional bile duct carcinomas arising from flat dysplasia. Given their significant risk of harboring invasive carcinoma, they should be treated with complete resection. (HEPATOLOGY 2012)

Hotspot activating PRKD1 somatic mutations in polymorphous low-grade adenocarcinomas of the salivary glands

Polymorphous low-grade adenocarcinoma (PLGA) is the second most frequent type of malignant tumor of the minor salivary glands. We identified PRKD1 hotspot mutations encoding p.Glu710Asp in 72.9% of PLGAs but not in other salivary gland tumors. Functional studies demonstrated that this kinase-activating alteration likely constitutes a driver of PLGA.

Papillary thyroid carcinomas with cervical lymph node metastases can be stratified into clinically relevant prognostic categories using oncogenic BRAF, the number of nodal metastases, and extra-nodal extension.

BACKGROUND Papillary thyroid carcinoma (PTC) patients presenting with cervical lymph nodes (LN) metastases (M) have a variable outcome. The objective of this study is to assess the value of meticulous histopathologic examination and genotyping in stratifying these patients into clinically relevant prognostic subgroups. METHODS This was a retrospective clinical and histopathological review of PTC patients with lymph node metastases at presentation identified between 1980 and 2002 in a single institution. Primary tumors from patients who later recurred were matched to a group of patients who did not recur and subjected to mass spectrometry genotyping encompassing the most significant oncogenes in thyroid carcinomas. RESULTS There were 246 patients who satisfied the inclusion criteria. The median follow-up was 10.8 years. The presence of >3 metastatic nodes was an independent predictor of decreased recurrence free survival (p=0.03). In patients <45 years, none of 45 with 1-2 metastatic LN recurred, including 26 patients followed for a median of 13 years without radioactive iodine (RAI) therapy. BRAF mutations were found in 28 (78%) of 36 genotyped tumors. Combined positivity for BRAF and extra-nodal extension was much stronger in predicting disease specific survival (DSS) (p=0.004) than the single analysis of BRAF (p=0.12) or extra-nodal extension (p=0.02). CONCLUSIONS (i) The number of metastatic LN is an independent predictor of recurrence in all age groups and identifies a subset of young patients with excellent prognosis who may not benefit from RAI therapy. (ii) Combined positivity for BRAF and extra-nodal extension has additive prognostic value in predicting DSS. (iii) Classification systems that assign the same magnitude of risk for recurrence or death to all patients with N1 disease should be revisited.

Invasion rather than nuclear features correlates with outcome in encapsulated follicular tumors: further evidence for the reclassification of the encapsulated papillary thyroid carcinoma follicular variant.

The prognosis of the encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) and its relationship to encapsulated follicular carcinoma (EFC) and follicular adenoma (FA) is subject to controversy. All EFVPTCs, EFCs, and FAs identified at a single institution between 1981 and 2003 were analyzed microscopically. A cohort of FAs from a different hospital was also examined. EFVPTCs were subdivided into noninvasive EFVPTC (NIEFVPTC) and invasive EFVPTC (IEFVPTC) displaying capsular/vascular invasion. There were 83 EFVPTCs (57 noninvasive, 26 invasive), 14 EFCs, and 52 FAs. Similar to FA, over a median follow-up of 9.5 years, none of the NIEFVPTCs manifested lymph node metastasis (LNM) or recurred. Furthermore, with a median follow-up of 10.5 years, none of 39 NIEFVPTCs without radioactive iodine therapy recurred. Four (15%) of 26 IEFVPTCs and none of 14 EFCs harbored distant metastasis (P = .29). There was no difference in LNM rate and degree of vascular or capsular invasion between IEFVPTC and EFC (P > .1). All 4 IEFVPTCs with adverse behavior presented with distant metastasis and no LNM. Sixteen percent of IEFVPTCs had poor outcome, whereas there was none in the NIEFVPTCs (P = .007). In conclusion, NIEFVPTC seems to behave similarly to FA, whereas IEFVPTC can metastasize and spread like EFC. Thus, invasion rather than nuclear features drives outcome in encapsulated follicular tumors. Non-IEFVPTC could be treated in a conservative manner sparing patients unnecessary total thyroidectomy and radioactive iodine therapy. The position of the EFVPTC in the classification of thyroid neoplasia should be reconsidered.

Immunohistochemistry as first-line screening for detecting colorectal cancer patients at risk for hereditary nonpolyposis colorectal cancer syndrome: a 2-antibody panel may be as predictive as a 4-antibody panel.

The utility of immunohistochemical detection of DNA mismatch repair proteins in screening colorectal cancer for hereditary nonpolyposis colorectal cancer (HNPCC) is being widely investigated. Currently, in both research and clinical settings, a 4-antibody panel that includes the 4 most commonly affected proteins (MLH1, MSH2, MSH6, and PMS2) is being used generally. On the basis of the biochemical properties of these proteins, we hypothesized that a 2-antibody panel, comprising MSH6 and PMS2, would be sufficient to detect abnormalities in all 4 proteins. We tested this hypothesis on a series of 232 colorectal carcinoma samples derived from 2 patient cohorts: (1) a prospectively accrued series of patients who were judged to carry a higher-than-average risk for HNPCC based on the revised Bethesda guidelines (n=190); and (2) a retrospective series of patients who were 40 years of age or younger (n=42). Immunohistochemical stains were regarded as negative (protein lost), when there was no nuclear labeling in tumor cells (with positive internal control). Overall, 70 of the 232 tumors demonstrated loss of at least one protein. The most common abnormality was concurrent loss of MLH1 and PMS2 (observed in 17% of the cases), followed by concurrent loss of MSH2 and MSH6 (6%). All MLH1 and MSH2-abnormal cases were also abnormal for PMS2 and MSH6, respectively, whereas 9 of 50 (18%) PMS2 and 6 of 20 (30%) MSH6-abnormal cases showed only isolated loss of PMS2 or MSH6 (with normal staining for MLH1 and MSH2). As such, our findings provide evidence that a 2-antibody panel (PMS2 and MSH6) is as effective as the current 4-antibody panel in detecting DNA mismatch repair protein abnormalities. Such a cost-effective approach carries significant implication, as immunohistochemistry is being widely used as first-line screening for HNPCC.

Invasive Carcinoma Arising in Intraductal Papillary Mucinous Neoplasms of the Pancreas: A Matched Control Study with Conventional Pancreatic Ductal Adenocarcinoma

Objective: The purpose of this study was to characterize the clinicopathological features of invasive carcinomas arising in intraductal papillary mucinous neoplasms of the pancreas (IPMN) by histological subtype of the invasive component and to compare the outcomes of these patients to a cohort of matched patients with conventional ductal pancreatic adenocarcinoma. Background: Two distinct histological subtypes of invasive carcinomas arising in IPMNs have been described, colloid carcinoma and tubular carcinoma. Previous reports have suggested prognostic differences between these 2 subtypes but a matched comparison of colloid carcinoma, tubular carcinoma, and conventional pancreatic adenocarcinoma has not been reported. Methods: The clinicopathological variables of 59 patients resected for an invasive component of IPMN were analyzed with detailed pathologic review of histopathologic subtype (colloid carcinoma and tubular carcinoma). Using a postresection pancreatic adenocarcinoma nomogram, patients with either tubular or colloid carcinoma were matched on a 1:1 basis with patients resected for conventional ductal pancreatic adenocarcinoma. Clinicopathological factors and overall outcome was analyzed between the matched groups. Results: Fifty-nine patients underwent resection for IPMN with an associated invasive carcinoma (IPMN-INV). The estimated 3- and 5-year survival rates were 76% and 68%, respectively. Tubular carcinoma was present in 35 patients (59%) and 24 patients (41%) had colloid carcinoma. Tubular carcinoma subtype [hazard ratio (HR) 3.7, 95% confidence interval (CI) 1.2–11.6] and the presence of positive regional lymph nodes (HR 3.2 95% CI 1.2–8.2) were clinicopathological factors predictive of decreased survival by multivariate analysis. The 5-year estimated survival rates for tubular carcinoma and colloid carcinoma were 55% and 87%, respectively (P = 0.01). When compared with patients with conventional ductal pancreatic ductal adenocarcinoma resected during the same time period matched by a prognostic nomogram, patients with colloid carcinoma had a significantly longer survival outcome compared with patients with conventional adenocarcinoma (P = 0.0001). By contrast, survival after resection between patients with the tubular subtype (3-year estimated survival, 61%) and the matched group with conventional adenocarcinoma (3-year estimated survival, 21%) (P = 0.87) was not statistically different. Conclusions: In this study, the colloid carcinoma histological subtype of invasive IPMN had a more statistically favorable survival outcome than the tubular subtype. Patients with invasive tubular IPMN had no statistically significant difference in survival as matched patients with conventional ductal pancreatic carcinoma.