Interobserver variability in the diagnosis of crypt dysplasia in Barrett esophagus.

Recent morphologic and molecular evidence suggests that dysplasia in Barrett esophagus (BE) begins in the bases of the crypts [crypt dysplasia (CD)] and progresses with time to involve the upper portions of the crypts and surface epithelium. The aim of this study was to evaluate the criteria and reproducibility of diagnosing CD among 6 gastrointestinal pathologists, all with research interest in BE. Six gastrointestinal pathologists evaluated 2 clinical study sets, the first consisting of 40 BE cases [BE: 10, CD: 9, low-grade dysplasia (LGD): 10, high-grade dysplasia (HGD); 9, and intramucosal adenocarcinoma; 2] and the second consisting of 63 cases (BE: 16, CD: 15, LGD: 15, HGD: 15, and intramucosal adenocarcinoma: 2), at least 4 months apart. In between evaluations, all of the pathologists met at 1 hospital (consensus conference) to review the areas of disagreement and establish more objective criteria. Overall, the level of agreement for all cases was moderate (κ=0.44), and the level of agreement did not change significantly after evaluation of the second study set. The highest levels of agreement were obtained for lesions at the low and high end of the spectrum (BE without dysplasia and HGD). Overall, the degree of agreement for CD was moderate after both the first and second study set review (κ=0.44 and 0.46, respectively). However, the degree of agreement for CD was higher than that obtained for LGD in both study sets. In the first study set, 4 or more pathologists agreed with the original CD diagnosis in 78% of cases, and this value did not change significantly after review of the second study set. The observers agreed that characteristic features of CD include the presence of unequivocal dysplastic cells, similar in appearance to traditional LGD, involving any part, or all of the length, of the crypt in the absence of intercrypt surface epithelial involvement. Rare cases of CD may show high-grade cytologic features composed of markedly enlarged nuclei with increased nuclear/cytoplasmic ratio, eosinophilic cytoplasm, irregular nuclear membranes, and loss of polarity. The findings in this study suggest that CD can be diagnosed reliably with a moderate level of interobserver agreement. Long-term and multi-institutional studies should be carried out to further determine the biological and clinical significance and natural history of CD in patients with BE.

Smoothelin is a specific marker for smooth muscle neoplasms of the gastrointestinal tract.

Smoothelin is a smooth muscle-specific cytoskeletal protein exclusively found in differentiated smooth muscle cells. This contrasts with other smooth muscle proteins (eg, h-caldesmon, alpha-smooth muscle actin, desmin, smooth muscle myosin), which are expressed in proliferative (early) stages of smooth muscle development and occasionally in other cell types (striated muscle, myofibroblasts, myoepithelial cells, pericytes). Smoothelin has been shown to be expressed predominantly in visceral smooth muscle and to a lesser extent in vascular smooth muscle. Smoothelin expression in mesenchymal tumors of the gastrointestinal (GI) tract has not been evaluated earlier. The purpose of this study was to determine whether immunostaining for smoothelin could help distinguish smooth muscle neoplasms from their morphologic mimics, particularly KIT-negative gastrointestinal stromal tumors (GISTs), desmin-positive GISTs, and desmoid fibromatosis. A total of 150 mesenchymal neoplasms of the GI tract, abdominal cavity, and retroperitoneum were retrieved from consult and surgical pathology archives, including 54 GISTs (8 KIT-negative; 13 desmin-positive), 17 GI leiomyosarcomas (LMS), 11 GI mural leiomyomas, 13 leiomyomas of the muscularis mucosae, 12 gastric schwannomas, 15 inflammatory myofibroblastic tumors, 9 cases of mesenteric desmoid fibromatosis, 10 dedifferentiated liposarcomas, and 9 malignant peripheral nerve sheath tumors. Immunostaining for smoothelin was performed on all cases. Cytoplasmic and nuclear staining was recorded. Cytoplasmic expression of smoothelin was present in all 24 (100%) benign smooth muscle tumors (mural leiomyomas and leiomyomas of the muscularis mucosae). In contrast, only 4 (24%) GI LMS showed cytoplasmic staining for smoothelin. None of the GISTs, desmoid tumors, inflammatory myofibroblastic tumors, schwannomas, dedifferentiated liposarcomas, or malignant peripheral nerve sheath tumors showed cytoplasmic reactivity for smoothelin. Interestingly, 7 (41%) GI LMS and 12 (22%) GISTs (all except 2 with an epithelioid component) showed multifocal, exclusively nuclear staining for smoothelin. Nuclear expression of smoothelin was not detected in any of the other tumor types examined. In summary, diffuse cytoplasmic staining for smoothelin is highly sensitive and specific for benign leiomyomas of the GI tract. Aberrant nuclear expression is common in GI LMS and may also be seen in GISTs, especially epithelioid and mixed-type tumors. These findings suggest that the extent and pattern of smoothelin expression may help differentiate between benign and malignant mesenchymal tumors of the GI tract, and may be useful in distinguishing leiomyomas from KIT-negative and/or desmin-positive GISTs.

Identification of c-kit gene mutations in primary adenoid cystic carcinoma of the salivary gland.

The CD117 (KIT) protein is overexpressed in many human neoplasms including adenoid cystic carcinoma of salivary glands. To evaluate the function of c-kit-activating mutations in adenoid cystic carcinoma of the salivary gland, we studied 14 cases (13 primary, 1 cervical lymph node metastasis) from our institution. KIT protein expression was evaluated by immunohistochemistry using formalin-fixed paraffin-embedded tissue. Mutational analyses of c-kit extracellular (exon 9), juxtamembrane (exon 11) and tyrosine kinase domains (exons 13 and 17) were performed by polymerase chain reaction, clonal selection and DNA sequencing. All 14 cases demonstrated strong KIT expression by immunohistochemistry. Molecular analysis was successful in 8 of 14 cases, and c-kit missense point mutations were detected in seven of eight cases (88%) including seven in exon 11, two in exon 9, two in exon 13 and two in exon 17. Eight silent point mutations were detected in five cases. Two cases contained missense mutations in more than one exon. Different mutations were found in the primary tumor and the cervical lymph node metastasis of one patient. Point mutations in domains similar to those described in gastrointestinal stromal tumors were detected, including Pro551Leu and Lys558Glu (5' end of exon 11), Leu576Phe (3' end of exon 11), Val643Ala (exon 13) and Asn822Ser (exon 17). Additional novel point mutations in exons 9, 11, 13 and 17 were also identified. This study is the first to report c-kit gene mutations in primary adenoid cystic carcinoma of the salivary gland. Identification of such potential gain-of-function mutations in exon 11, and less frequently in exons 9, 13 and 17, suggests that KIT may be involved in the pathogenesis of adenoid cystic carcinoma of salivary glands. Our study raises a prospect of correlation of c-kit mutation and a potential treatment of adenoid cystic carcinoma with tyrosine kinase inhibitor (imatinib).