A case of fetal twin-to-twin cytomegalovirus infection through a dichorionic diamniotic (DiDi)-fused placenta prompted our search for possible vascular anastomoses in this type of placenta. This case and three additional DiDi-fused placentas were studied with gross (macro) sections and a three-dimensional (3D) stereomicroscopic technique. Two twins were dizygotic (they differed in gender and blood groups) and the other two were probably monozygotic. Macrosections and 3D-image analysis demonstrated side-to-side connections between small subchorionic vessels. These findings demonstrate that vascular anastomoses are present in DiDi-fused placentas.
[Show abstract][Hide abstract] ABSTRACT: Large format sections (LS) first have been introduced in breast pathology more than a century ago. Since then, they constituted for longtime a research tool to better understand breast microanatomy and the relationship between radiological images and pathological features. Similarly LS have been used to study neoplastic, inflammatory, and degenerative diseases affecting various organs, as brain, lung, gastrointentinal tract, bone, urinary tract, prostate, and placenta. Currently LS are mostly applied to diagnostic routine to better stage tumours such as prostate and breast carcinomas or to correlate radiologic imaging to gross specimens. The purpose of the present paper is to review the historical background and the basis of the applications of LS in surgical pathology, with special emphasis on breast tumours.
"It does not happen that way. Anastomosis of placental circulation has been found to have happened only a handful of times in examination of several thousand fused dichorionic dizygotic placentas (Foschini et al., 2003). "
" It has , however , become clear that chimeras among delivered DZ twins are far more common ( van Dijk et al . , 1996 ) than blood vessel anasto - moses between dichorionic placentas ( Robertson and Neer , 1983 ; Bjoro and Bjoro , 1985 ; Lage et al . , 1989 ; Benirschke , 1990 , 1992 , 1995 ; Machin et al . , 1995 ; Benirschke and Masliah , 2001 ; Foschini et al . , 2003 ) . There are nowhere near enough anastomoses between dichorionic placentas to account for the observed frequency of chimeras . This can reasonably be considered to refute that traditional supposition . Reports of finding chimerism only in blood arise overwhelmingly from situations in which no tissue other than blood was examined ."
[Show abstract][Hide abstract] ABSTRACT: Human spontaneous chimerism, with one body built from cells of both twins of a dizygotic (DZ) pair, is supposed to be extremely rare, arising from the exchange of blood cells through placental anastomoses. Mosaicism is supposed to be far more common, arising from single zygotes by embryonic mutation. Because typical diagnosis of mosaicism can neither identify nor exclude chimerism, 'mosaicism' may often be chimerism undiscovered. Evidence shows chimerism arises primarily from DZ embryo fusion and is not rare, although it has negligible probability under the hypothesis of independent double ovulation and independent embryogenesis. If, instead, DZ twin embryos begin development as a single cell mass, chimerism is likely. This would be consistent with observations that DZ twins develop as differently from singletons as monozygotic twins do with regard to embryogenic establishment of asymmetries of midline neural-crest-driven structures of brain, face and heart. Chimerism is a significant component of human embryonic development that deserves closer attention as a mechanism of developmental variation. The 'common knowledge' understanding of twinning mechanisms is at best inadequate. The importance of the difference lies in what we can learn from chimerism about human embryogenesis and the cellular origins of structures and functions basic to the business of becoming human.
Human Reproduction 04/2006; 21(3):579-91. DOI:10.1093/humrep/dei370 · 4.57 Impact Factor
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