On the origin of cardiac mucosa: A histological and immunohistoc-hemical study of cytokeratin expression patterns in the developing esophagogastric junction region and stomach

AIM： To examine the fetal and neonatal esophagogastric junction region （EGJ） histologically for the presence of an equivalent to adult cardiac mucosa （CM）; to study the expression patterns of all cytokeratins （CK） relevant to the EGJ during gestation; to compare the CK profile of the gestational and the adult EGJ; and to determine the degree of development in the adult EGJ histology and CK profile during gestation. METHODS： Forty-eight fetal autopsy specimens of the EGJ were step-sectioned and stained with hematoxylin and eosin （H＆E） to select sections showing the mucosal lining. Immunohistochemistry for CK5, 7, 8, 13, 18, 19, and 20 was performed. Antibody staining was then graded for location, intensity, and degree. RESULTS： The distal esophagus was lined by simple columnar epithelium from 12-wk gestational age （GA）. The proximal part of this segment consisted of mucusproducing epithelium, devoid of parietal cells. CK5 and 13 were present exclusively in multilayered epithelia and CK8, 18, and 19 predominantly in simple columnar epithelium. There were no differences in the frequencies of the coordinate CK7＋/20＋ and the CK7-/20- immunophenotypes between different locations. The prevalence of the CK7＋/ 20- immunophenotype decreased, and that of the CK7-/ 20＋ immunophenotype increased significantly from the distal esophagus to the distal stomach. CONCLUSION： Fetal columnar-lined lower esophagus （fetal CLE） may be the equivalent and precursor of the short segments of columnar epithelium found in the distal esophagus of some normal adult subjects. Esophageal simple columnar epithelium without parietal cells （ESN） may be the precursor of adult CM. The similarities between the fetal and adult EGJ and stomach CK expression pattems support the conclusion that adult CN has an identifiable precursor in the fetus. This would then indicate that at least a part of the adult CM has a congenital origin.

T(11;18)(q21;q21)-positive gastrointestinal MALT lymphomas are heterogeneous with respect to the V_H gene mutation status

AIM: To investigate how t(11;18)(q21;q21)-positive gastrointestinal MALT lymphomas relate to other marginal zone lymphomas with respect to the somatic mutation pattern of the VH genes and the expression of the marker CD27. METHODS: The VH gene of 7 t(11;18)(q21;q21)-positive gastrointestinal MALT lymphomas was amplif iedby PCR using family specif ic VH primers and a consensus JH primer. PCR products were sequenced and mutation analysis of the CDR and the FR regions was performed. All cases were immunostained for CD27. RESULTS: One case showed unmutated VH genes while the others showed mutated VH genes with mutation frequencies ranging from 1.3 to 14.7% and with evidence of antigen selection in 2 cases. These data suggest that the translocation t(11;18)(q21;q21) can target either B-cells at different stages of differentiation or naive B-cells that retain the capacity to differentiate upon antigen stimulation. All cases but one displayed weak to strong CD27 expression which did not correlate with the VH gene mutation status. CONCLUSION: t(11;18)(q21;q21)-positive gastro- intestinal MALT lymphomas are heterogeneous with respect to the VH mutation status and CD27 is not a marker of somatically mutated B-cells.