Hepatocellular carcinomas exhibit heterogeneous morphologies by routine light microscopy. Although some morphologies represent insignificant variations in growth patterns, others may represent unrecognized subtypes of hepatocellular carcinoma. Identification of these subtypes could lead to separation of hepatocellular carcinomas into discrete groups with unique underlying genetic changes, prognosis, or therapeutic responses. In order to identify potential subtypes, two pathologists independently screened a cohort of 219 unselected hepatocellular carcinoma resection specimens and divided cases into potential subtypes. One of these promising candidate subtypes was further evaluated using histological and molecular techniques. This subtype was characterized by a unique and consistent set of histological features: smooth chromophobic cytoplasm, abrupt focal nuclear anaplasia (small clusters of tumor cells with marked nuclear anaplasia in a background of tumor cells with bland nuclear cytology), and scattered microscopic pseudocysts-we designate this variant as 'chromophobe hepatocellular carcinoma with abrupt anaplasia'. Thirteen cases were identified (6% of all hepatocellular carcinomas), including 6 men and 7 women with an average age of 61 years. Six cases occurred in cirrhotic livers. Serum AFP was elevated in 6 out of 10 cases. There were a variety of underlying liver diseases, but cases were enrichment for chronic hepatitis B, P=0.006. Interestingly, at the molecular level, this variant was strongly associated with the alternative lengthening of telomere (ALT) phenotype by telomere FISH. ALT is a telomerase-independent mechanism of telomere maintenance and is found in approximately 8% of unselected hepatocellular carcinomas. In contrast, 11/12 (92%) of the cases of chromophobe hepatocellular carcinoma with abrupt anaplasia were ALT-positive. In summary, we propose that chromophobe hepatocellular carcinoma with abrupt anaplasia represents a new subtype of hepatocellular carcinoma with unique morphological and molecular features.Modern Pathology advance online publication, 3 May 2013; doi:10.1038/modpathol.2013.68.

KRAS mutations define a clinically distinct subgroup of lung adenocarcinoma patients, characterized by smoking history, resistance to EGFR-targeted therapies, and adverse prognosis. Whether KRAS-mutated lung adenocarcinomas also have distinct histopathological features is not well established. We tested 180 resected lung adenocarcinomas for KRAS and EGFR mutations by high-sensitivity mass spectrometry-based genotyping (Sequenom) and PCR-based sizing assays. All tumors were assessed for the proportion of standard histological patterns (lepidic, acinar, papillary, micropapillary, solid, and mucinous), several other histological and clinical parameters, and TTF-1 expression by immunohistochemistry. Among 180 carcinomas, 63 (35%) had KRAS mutations (KRAS+), 35 (19%) had EGFR mutations (EGFR+), and 82 (46%) had neither mutation (KRAS-/EGFR-). Solid growth pattern was significantly over-represented in KRAS+ carcinomas: the mean±s.d. for the amount of solid pattern in KRAS+ carcinomas was 27±34% compared with 3±10% in EGFR+ (P<0.001) and 15±27% in KRAS-/EGFR- (P=0.033) tumors. Furthermore, at least focal (≥20%) solid component was more common in KRAS+ (28/63; 44%) compared with EGFR+ (2/35; 6%; P<0.001) and KRAS-/EGFR- (21/82; 26%; P=0.022) carcinomas. KRAS mutations were also over-represented in mucinous carcinomas and were significantly associated with the presence of tumor-infiltrating leukocytes and heavier smoking history. EGFR mutations were associated with non-mucinous non-solid patterns, particularly lepidic and papillary, lack of necrosis, lack of cytological atypia, hobnail cytology, TTF-1 expression, and never/light smoking history. In conclusion, extended molecular and clinicopathological analysis of lung adenocarcinomas reveals a novel association of KRAS mutations with solid histology and tumor-infiltrating inflammatory cells and expands on several previously recognized morphological and clinical associations of KRAS and EGFR mutations. Solid growth pattern was recently shown to be a strong predictor of aggressive behavior in lung adenocarcinomas, which may underlie the unfavorable prognosis associated with KRAS mutations in these tumors.Modern Pathology advance online publication, 26 April 2013; doi:10.1038/modpathol.2013.74.

Recently, we characterized fibroblast growth factor receptor 1 amplification as a target for a rational therapy in lung squamous cell carcinoma. Patients harboring this genetic event are currently eligible for treatment with antifibroblast growth factor receptor small-molecule inhibitors in phase I clinical trials. This has the potential to significantly improve standard therapy for lung squamous cell carcinoma patients. The aim of this study was to elucidate whether fibroblast growth factor receptor 1 amplification is also a common genetic event in head and neck squamous cell carcinoma. For this purpose, we assembled a cohort of 555 patients, including 264 with metastatic disease and 147 with recurrent disease. Formalin-fixed, paraffin-embedded material of primary tumors, metastases and recurrences were assessed for fibroblast growth factor receptor 1 copy number status using fluorescence in situ hybridization. Human papilloma virus status was detected by p16 immunohistochemistry staining and PCR-ELISA. Molecular parameters were correlated with each other and with clinicopathological data. We found 15% of primary head and neck squamous cell carcinoma to display a fibroblast growth factor receptor 1 amplification. In nearly all cases, metastatic and recurrent tumor samples shared the same amplification status as the corresponding primary tumor. Fibroblast growth factor receptor 1 amplification was associated with nicotine and alcohol consumption, but was mutually exclusive with human papilloma virus infection. Amplification of the gene was associated with parameters of worse outcome. Our data identify fibroblast growth factor receptor 1 amplification as a frequent event in primary and metastatic head and neck squamous cell carcinoma and represents a potential biomarker for more aggressive disease. Fibroblast growth factor receptor 1-amplified tumors could potentially comprise a subset of head and neck squamous cell carcinoma against which targeted small-molecule inhibitors hold therapeutic efficacy.Modern Pathology advance online publication, 26 April 2013; doi:10.1038/modpathol.2013.58.

Basal cell carcinoma of the anal region is rare and morphologically difficult to distinguish from basaloid squamous cell carcinoma, particularly on biopsies. This distinction has therapeutic and prognostic implications. We reviewed morphological features of 9 basal cell carcinomas and 15 basaloid squamous cell carcinomas from the anal region diagnosed during 1993-2011 and determined the utility of Ber-EP4, BCL2, TP63, CK5/6, CDKN2A, and SOX2 as diagnostic tools. Immunostains were scored in a semi-quantitative manner (1+-1-10%, 2+-11-50%, 3+->50%). All basal cell carcinomas were located in the perianal region, while all basaloid squamous cell carcinomas originated in the anal canal/anorectum. Nodular subtype of basal cell carcinoma was the most common subtype. Retraction artifact was the only significant distinguishing histological feature of basal cell carcinoma compared with basaloid squamous cell carcinoma (88% vs 26%; P=0.04). Atypical mitoses were more common in basaloid squamous cell carcinomas (71% vs 11%; P=0.05). An in situ component was only present in basaloid squamous cell carcinomas, and was noted in 6/15 cases. Basal cell carcinomas had 2-3+ Ber-EP4 (basal cell carcinoma 100% vs basaloid squamous cell carcinoma 40%; P<0.001) and BCL2 immunoreactivity (basal cell carcinomas 100% vs basaloid squamous cell carcinoma 33%; P<0.001). Diffuse CDKN2A and SOX2 expression was seen only in basaloid squamous cell carcinomas (basal cell carcinoma 0% vs basaloid squamous cell carcinoma 93%; P<0.001). There was no difference in TP63 and CK5/6 expression. Perianal location, retraction artifact, and lack of atypical mitoses are histological features that help distinguish basal cell carcinoma from basaloid squamous cell carcinoma. An in situ component, when present, supports the diagnosis of basaloid squamous cell carcinoma. Immunostains are extremely helpful as diffuse Ber-EP4 and BCL2 expression is a feature of basal cell carcinoma and basaloid squamous cell carcinoma is typified by diffuse CDKN2A and SOX2 expression.Modern Pathology advance online publication, 19 April 2013; doi:10.1038/modpathol.2013.75.

This study evaluated an unusual subset of oral epithelial dysplasia for the presence of transcriptionally active high-risk HPV subtypes and to further characterize the histological criteria for this condition. There were 20 cases diagnosed as epithelial dysplasia with marked apoptosis of the anterior oral cavity. Clinical and follow-up data were collected and histopathological features were documented. Immunoperoxidase studies were performed for p16 and in situ hybridization studies were performed for low- and high-risk HPV sub-types. Gender- and site-matched controls of conventional moderate-to-severe oral epithelial dysplasia were similarly evaluated using immunoperoxidase studies for p16 and in situ hybridization; the number of apoptotic cells for study and control cases was counted at two different tissue sites. There were 17 men and 3 women with a median age of 56 years. Seventeen lesions were described as white and five were described as rough or papillary. Thirteen were located on the lateral or ventral tongue, some extending onto the floor of the mouth. Epithelial hyperplasia with marked karyorrhexis and apoptosis were present in all the cases, along with features of conventional oral epithelial dysplasia. A statistically significant number of apoptotic cells were identified in the study cases when compared with controls (P>0.0001). Twenty cases were positive for high-risk HPV by in situ hybridization and all 19 nineteen cases evaluated for p16 demonstrated overexpression. Two patients were diagnosed with squamous cell carcinomas and one patient developed recurrent disease. We report a subset of oral epithelial dysplasia that occurs mostly in adult men on the ventral or lateral tongue and is positive for high-risk HPV and for p16. We propose use of the term 'HPV-associated Oral Intraepithelial Neoplasia' to characterize these lesions of the oral cavity for consistency in nomenclature with HPV-associated lesions of the lower anogenital tract. One case recurred and one developed invasive cancer.Modern Pathology advance online publication, 19 April 2013; doi:10.1038/modpathol.2013.70.

Endometrial stromal sarcomas represent the second most common mesenchymal uterine tumor. The 2003 WHO classification distinguishes low-grade and undifferentiated endometrial stromal sarcomas with different prognoses. Endometrial stromal sarcomas are a genetically heterogeneous group of sarcomas harboring different cytogenetic anomalies. Recently, a fusion between the YWHAE and FAM22A/B genes subsequent to a t(10;17) (q22;p13) has been described in endometrial sarcomas with high-grade histology. We examined YWHAE rearrangements by FISH break-apart and RT-PCR in a series of 27 undifferentiated uterine stromal sarcoma without JAZF1 rearrangements. Immunohistochemistry (IHC) was carried out with a panel of antibodies (estrogen (ER) and progesterone (PR) receptors, CD10, Cyclin D1, β-catenin, p53, and Ki-67). We identified a subgroup of endometrial sarcomas with high-grade histology and uniform morphology harboring YWHAE rearrangements. FISH break-apart was interpretable in 20 cases (74%). Twelve cases (60%) showed <10% of tumor cells with a YWHAE rearrangement, 4 cases (20%) showed between 10 and ≤20%, and 4 (20%) >20%. RT-PCR was tested on 24/27 cases (88%) and 19 cases were interpretable (79%). Five cases (26%) showed a specific fusion transcript YWHAE-FAM22A/B sequence. The best concordance rate between FISH and RT-PCR (94%) was obtained with the threshold of 20% of cells with a YWHAE rearrangement. The YWHAE-rearranged cases showed high-grade morphology with uniform appearance, spindle or round epithelioid cells, low ER and PR, CD10 expression, and a high and diffuse positivity for Cyclin D1, p53, and nuclear β-catenin negativity. Cyclin D1 was the most sensitive marker for high-grade endometrial sarcomas with YWHAE rearrangement. All undifferentiated uterine sarcomas with pleomorphic appearances did not harbor any YWHAE rearrangements, except for one case. Overall, for endometrial sarcoma cases with high-grade morphology we recommend to test for YWHAE rearrangements by FISH break-apart, a cost- and time-efficient method, and to complete the investigation by RT-PCR in borderline cases.Modern Pathology advance online publication, 19 April 2013; doi:10.1038/modpathol.2013.69.

Lymph node staging is of paramount importance for prognosis estimation and therapy stratification in colorectal cancer. A high number of harvested lymph nodes is associated with an improved outcome. Methylene blue-assisted lymph node dissection effectively improves the lymph node harvest and ensures sufficient staging. Now, the effect on node positivity rate and stage-related outcome was investigated. The study cohort with advanced lymph node dissection consisted of 669 colorectal cancer cases of all stages, which were collected between 2007 and 2012. A historical collection of 663 cases investigated with conventional techniques between 2002 and 2004 served as control. Lymph node harvest was dramatically improved in the study group with mean lymph node numbers of 34±17 vs 13±5 (P<0.001) and sufficient staging rates of 98% vs 62% (P<0.001). However, neither the rate of nodal positive cases (37% vs 37%; P=0.98) nor the rate of N2 cases differed between the two groups (14% vs 13%; P=0.80). Furthermore, no differences were found concerning the outcome in both groups. The advanced lymph node dissection technique guarantees adequate histopathological lymph node staging in virtually all cases of colorectal cancer and is therefore extremely helpful. The hypothesis that it also provides a higher sensitivity in detecting metastases, however, could be not proved.Modern Pathology advance online publication, 19 April 2013; doi:10.1038/modpathol.2013.61.

GATA3 is a zinc-finger transcription factor, which is expressed in various normal and neoplastic tissues. Amongst tumors, it labels urothelial carcinoma, collecting duct carcinoma of the kidney, breast carcinoma, lymphoma and, uncommonly, endometrial carcinoma. Few studies have investigated its positivity in various neoplasms that may mimic urothelial neoplasms. In this study, we evaluated GATA3 expression in urinary bladder paragangliomas, which may closely mimic urothelial carcinomas. We retrieved 12 cases of paragangliomas from the urinary bladder and 20 cases of paragangliomas from non-urologic sites using the Hopkins Pathology Data Base system. GATA3 was positive in 10 of the 12 (83%) urinary bladder paragangliomas studied on routine slide sections. Most (6/12) of the staining was diffusely strong (3+) staining, whereas the rest (4/12) that were positive showed mixed intensities (strong 3+ to moderate 2+). The 20 paragangliomas from other sites were constructed into tissue microarrays, wherein three cores from each tumor were taken. Fifteen out of 20 (75%) paragangliomas outside of the bladder were positive for GATA3 staining. Moderate (2+) or strong (3+) staining was seen in 13/20 (65%) of extravesical paragangliomas, ranging from 5 to 100% of the cell labeling (mean 59%, median 60%). In the remaining 7/20 (35%) cases, only weak (2/7) or negative (5/7) immunoreactivity for GATA3 was seen. An additional 15 cases of metastatic paraganglioma from various primary sites were retrieved with 12 of 15 (80%) metastatic paragangliomas staining positively for GATA3. Overall, for paragangliomas, regardless of site, 78.7% were positive for GATA3. Recognition of this finding will aid pathologists in preventing a misdiagnosis of a urothelial tumor based on GATA3 expression, which is critical given the differences in treatment, follow-up and prognosis between bladder paragangliomas and urothelial carcinoma.Modern Pathology advance online publication, 19 April 2013; doi:10.1038/modpathol.2013.76.

Peutz-Jeghers syndrome is an autosomal dominant condition characterized by gastrointestinal hamartomatous polyps. The pathologic identification of a Peutz-Jeghers polyp is integral to the diagnosis of this syndrome that often remains undiagnosed until after these polyps are identified. Histologically, Peutz-Jeghers polyps are characterized by a distinctive arborization of smooth muscle within the lamina propria. Colonic Peutz-Jeghers polyps, however, may mimic mucosal prolapse polyps or virtually any colonic polyp that undergoes prolapse. In this paper, we explore the morphological features of colonic Peutz-Jeghers polyps and the diagnostic challenges associated with these polyps. Colonic polyps from patients with Peutz-Jeghers syndrome were identified (n=34). The control cohort, included mucosal prolapse polyps (n=5), hyperplastic polyps (n=10) and tubular adenomas with prolapse (n=9), ganglioneuromatous polyps (n=2) and juvenile polyps (n=14). Intramucosal smooth muscle fibers were identified in all classes of polyps. Twenty-three of the 34 colonic Peutz-Jeghers polyps were characterized by lobulated clusters of colonic crypts. On immunohistochemistry, desmin-positive smooth muscle fibers were seen surrounding these lobules. This lobular organization of the crypts was not identified in mucosal prolapse polyps and hyperplastic polyps or tubular adenomas with prolapse; only one of the 14 juvenile polyps showed this pattern of reactivity on a desmin stain. Our data suggests that the histologic hallmark of colonic Peutz-Jeghers polyps is the lobular organization of the crypts, and that an arborizing pattern of smooth muscle proliferation is neither sensitive nor a specific marker of colonic Peutz-Jeghers polyps. The presence of desmin-positive smooth muscle fibers surrounding the lobules is a helpful diagnostic feature of colonic Peutz-Jeghers polyps, and facilitates the distinction of these polyps from non-Peutz-Jeghers polyps with prolapse-like changes.Modern Pathology advance online publication, 19 April 2013; doi:10.1038/modpathol.2013.44.

Loss of PTEN (phosphatase and tensin homolog) expression and microsatellite instability are two of the more common molecular alterations in endometrial carcinoma. From the published literature, it is controversial as to whether there is a relationship between these different molecular mechanisms. Therefore, a cohort of 187 pure endometrioid and non-endometrioid endometrial carcinomas, carefully characterized as to clinical and pathological features, was examined for PTEN sequence abnormalities and the immunohistochemical expression of PTEN and the DNA mismatch repair proteins MLH1, MSH2, MSH6, and PMS2. MLH1 methylation analysis was performed when tumors had loss of MLH1 protein. Mismatch repair protein loss was more frequent in endometrioid carcinomas compared with non-endometrioid carcinomas, a difference primarily attributable to the presence of MLH1 methylation in a greater proportion of endometrioid tumors. Among the non-endometrioid group, mixed endometrioid/non-endometrioid carcinomas were the histotype that most commonly had loss of a mismatch repair protein. In endometrioid tumors, the frequency of PTEN loss measured by immunohistochemistry and mutation did not differ significantly between the mismatch repair protein intact or mismatch repair protein loss groups, suggesting that PTEN loss is independent of mismatch protein repair status in this group. However, in non-endometrioid carcinomas, both intact positive PTEN immunohistochemical expression and PTEN wild type were highly associated with retained positive expression of mismatch repair proteins in the tumor. Relevant to screening endometrial cancers for Lynch Syndrome, an initial PTEN immunohistochemistry determination may be able to replace the use of four mismatch repair immunohistochemical markers in 63% of patients with non-endometrioid endometrial carcinoma. Therefore, PTEN immunohistochemistry, in combination with tumor histotype, is a useful adjunct in the clinical evaluation of endometrial carcinomas for Lynch Syndrome.Modern Pathology advance online publication, 19 April 2013; doi:10.1038/modpathol.2013.67.