ABSTRACT
Gestational trophoblastic disease comprises a heterogeneous group of lesions arising from abnormal proliferation of trophoblastic cells. An elevation of human chorionic gonadotropin after evacuation of a molar pregnancy should suggest the hypothesis of a persistent gestational trophoblastic neoplasia. We present a rare case of coexistence of choriocarcinoma and placental-site trophoblastic tumor in the same tumor, whose diagnosis was made based on the correlation of morphological, microscopic and immunocytochemical studies, due to the difficulty in diagnosing these mixed tumors based on conventional histology only.
A doença trofoblástica gestacional compreende um grupo heterogêneo de lesões decorrentes da proliferação anormal de células trofoblásticas. A elevação da subunidade beta da gonadotrofina coriônica humana (β-hCG) após a evacuação de uma gravidez molar levanta a hipótese diagnóstica de neoplasia trofoblástica gestacional persistente. Apresentamos um caso raro de coexistência de coriocarcinoma e tumor trofoblástico do leito placentário em um mesmo tumor, cujo diagnóstico foi efetuado com base na correlação dos estudos morfológicos, microscópicos e imuno-histoquímicos, dada a dificuldade de diagnosticar esses tumores mistos com base apenas no exame histológico convencional.
ABSTRACT
El nucléolo, considerado únicamente como el sitio de síntesis de los ribosomas, actualmente representa una estructura nuclear dinámica que participa en la regulación de importantes procesos celulares. Numerosas evidencias han demostrado que el envejecimiento celular es una de las diversas funciones que son controladas por el nucléolo. Las mutaciones en las proteínas de localización nucleolar promueven el envejecimiento prematuro en levaduras y humanos. La carencia de represión en la transcripción de genes que codifican para el ARNr que se encuentran dañados, y las mutaciones en las helicasas del ADN encargadas de minimizar la formación de círculos extra-cromosómicos del ADN que codifica para el ARNr, provocan modificaciones en la estructura del nucléolo e inducen envejecimiento prematuro en levaduras. De igual manera, en los humanos la carencia de las helicasas del ADN localizadas en el nucléolo y que participan en el mantenimiento de la integridad genómica, favorecen el desarrollo de aquellas enfermedades asociadas con el envejecimiento acelerado. Además, la presencia de algunos componentes de la telomerasa en el nucléolo, indica que parte de la biosíntesis de esta enzima se realiza en esta estructura nuclear, sugiriendo una conexión entre el nucléolo y la síntesis de los telómeros en la regulación del envejecimiento celular. Por otra parte, el nucléolo secuestra proteínas para regular su actividad biológica durante el inicio o término de la vida replicativa celular.
The nucleolus has been considered originally only as the site for the ribosome synthesis, but now it is well known that it represents a dynamic nuclear structure involved in important cellular processes. Several evidences have demonstrated that the nucleolus regulates the cellular senescence. Specific mutations on the DNAs codifying for nucleolar proteins induced premature senescence from yeast to human. The failure to repress the genes transcription codifying for damaged rRNA, and the mutations in DNA helicases, which minimizes the formation of DNA extra-chromosomal circles codifying for rRNA, modify the nucleolar structure and induce premature senescence in yeast. Similarly, in humans, the reduction of these DNA helicases levels, which are localized in the nucleoli and participate in maintenance of genomic integrity, helps to the development of those diseases associated with premature senescence. Furthermore, the presence in the nucleolus of some telomerase components, indicates that part of the biosynthesis of this enzyme occurred in this nuclear structure; suggesting a communication between the nucleolus and the synthesis of the telomeres in the regulation of cell senescence. On the other hand, the nucleolus sequesters proteins to regulate its own biological activity, from the start to the end of cellular replication. In addition this nuclear structure is involved in the biosynthesis of most cellular ribonucleoprotein particles, as well as in cell cycle regulation, making it central to gene expression. In conclusion, the nucleolus became a multifunctional subnuclear structure involved from cell proliferation to cell senescence.