A Narrative Review on the Clinical Relevance of Imaging the Circumventricular Brain Organs and Performing Their Anatomical and Histopathological Examination in Acute and Postacute COVID-19.

ABSTRACT: Autopsy followed by histopathological examination is foundational in clinical and forensic medicine for discovering and understanding pathological changes in disease, their underlying processes, and cause of death. Imaging technology has become increasingly important for advancing clinical research and practice, given its noninvasive, in vivo and ex vivo applicability. Medical and forensic autopsy can benefit greatly from advances in imaging technology that lead toward minimally invasive, whole-brain virtual autopsy. Brain autopsy followed by histopathological examination is still the hallmark for understanding disease and a fundamental modus operandi in forensic pathology and forensic medicine, despite the fact that its practice has become progressively less frequent in medical settings. This situation is especially relevant with respect to new diseases such as COVID-19 caused by the SARS-CoV-2 virus, for which our neuroanatomical knowledge is sparse. In this narrative review, we show that ad hoc clinical autopsies and histopathological analyses combined with neuroimaging of the principal circumventricular organs are critical to gaining insight into the reconstruction of the pathophysiological mechanisms and the explanation of cause of death (ie, atrium mortis) related to the cardiovascular effects of SARS-CoV-2 infection in forensic and clinical medicine.

Phenomena of Intussusceptive Angiogenesis and Intussusceptive Lymphangiogenesis in Blood and Lymphatic Vessel Tumors.

Intussusceptive angiogenesis (IA) and intussusceptive lymphangiogenesis (IL) play a key role in the growth and morphogenesis of vessels. However, there are very few studies in this regard in vessel tumors (VTs). Our objective is to assess the presence, characteristics, and possible mechanisms of the formation of intussusceptive structures in a broad spectrum of VTs. For this purpose, examples of benign and malignant blood and lymphatic VTs were studied via conventional procedures, semithin sections, and immunochemistry and immunofluorescence microscopy. The results demonstrated intussusceptive structures (pillars, meshes, and folds) in benign (lobular capillary hemangioma or pyogenic granuloma, intravascular papillary endothelial hyperplasia or Masson tumor, sinusoidal hemangioma, cavernous hemangioma, glomeruloid hemangioma, angiolipoma, and lymphangiomas), low-grade malignancy (retiform hemangioendothelioma and Dabska tumor), and malignant (angiosarcoma and Kaposi sarcoma) VTs. Intussusceptive structures showed an endothelial cover and a core formed of connective tissue components and presented findings suggesting an origin through vessel loops, endothelialized thrombus, interendothelial bridges, and/or splitting and fusion, and conditioned VT morphology. In conclusion, the findings support the participation of IA and IL, in association with sprouting angiogenesis, in VTs, and therefore in their growth and morphogenesis, which is of pathophysiological interest and lays the groundwork for in-depth molecular studies with therapeutic purposes.

Ectopic liver in a five-week-old embryo.

The first case of a placental tumor composed of benign hepatic tissue was published in 1986 and considered a placental benign hepatocellular adenoma. Since then, this lesion is better known as ectopic liver, and a total of 12 cases have been published. The ectopic liver located in the umbilical cord is an even rarer alteration, with only nine cases described to date. We report another case of ectopic liver, this time in an embryo of only five weeks of gestational age.

Synovial tumefactive extramedullary hematopoiesis associated to polycythemia vera.

The case of a 66-year-old male patient with a chronic myeloproliferative type polycythemia vera disorder, who after 2 years of evolution is developing a tumefactive extramedullary hematopoiesis (TEH) located in the synovial of the articulation in the right knee, is described. The tumor histologically consists of a relatively lax and edematous synovial structure diffusely infiltrated by mature and semimature hematopoietic cellular population. The simultaneous study of the bone marrow reveals medullar spaces full of hematopoietic cellularity, with a predominance of megakaryocytic and red series, and with the addition of severe reticulin fibrosis, facts that suggest a progression toward myelofibrosis. The TEH developed in tissues without a reticulum endothelial system is very uncommon. We provide data about the first case located in the synovial membrane and we review the literature regarding this pathologic entity.