The usual assumption that monochorionic twins are monozygotic has recently been questioned, based on blood group discordance in 3 of 12 monochorionic pairs. Therefore, this study evaluates the validity of zygosity diagnosis based on examination of placental membranes, and at the same time evaluates Weinberg's differential rule in a Danish consecutive twin series. All twin pairs, 265 like-sexed and 87 unlike-sexed pairs, born at Odense University Hospital, Denmark, from 1 January 1980 through 31 August 1988, were ascertained. In 229 like-sexed pairs, zygosity was determined by serological methods, and in 190 of these, the fetal membranes could be reliably classified. Fiftynine monochorionic twin pairs were identified and none of those pairs were discordant for any genetic markers. Therefore, we conclude that monochorionic twins can be considered monozygotic. The distribution of monozygotic and dizygotic pairs was in accordance with Weinberg's rule.

The present study aimed to examine possible changes in keratin expression during neoplastic transformation of the uterine mucosa and possible differences in keratin expression between endocervical and endometrial adenocarcinomas. Routinely processed specimens with normal morphology or neoplastic changes were stained immunohistochemically using 5 commercial antibodies to keratin-filaments of molecular weight 39-58 kD: CAM 5.2, RCK 102, MCA 144, PKE and PRE. We generally found a change in keratin expression during the neoplastic transformation, consisting of pronounced heterogeneity compared with normal epithelia. In distinguishing koilocytic atypia from CIN, RCK 102 (52.5, 58 Kd) may prove helpful as it stains neoplastic cells strongly and shows no reaction in koilocytic. Staining with the antibody CAM 5.2 (reactive with 39, 43, 50 kD filaments) may aid in distinguishing between cervical and endometrial adenocarcinomas. The former is stained uniformly; the latter shows a more variable staining.

A 30-yr-old woman presented with 2 consecutive miscarriages within 7 mo. Histopathologic examination of the placental tissue showed intracytoplasmic inclusion vacuoles with a strong reaction in Periodic acid-Schiff staining and a slightly pallor reaction in alcian blue staining. Additional molecular genetic analyses confirmed glycogen storage disease Type IV with the finding of compound heterozygosity for 2 mutations (c.691+2T>C and c.1570C>T, p.R524X) in the GBE1 gene. We conclude that glycogen storage disease Type IV can cause early miscarriage and that diagnosis can initially be made on histopathologic examination. Genetic analysis is required to confirm the diagnosis and to offer prenatal genetic testing in future pregnancies.

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An adenoid cystic carcinoma of the endometrium co-existing with an endometrioid adenocarcinoma is presented. Immunohistochemical staining for actin and keratin suggests a myoepithelial differentiation of tumour cells in adenoid cystic carcinoma.