Publications by authors named "George Stoyanov"

Article Synopsis
  • Divergent differentiation in urothelial carcinoma complicates accurate histopathological diagnosis, as traditional cancer features can be sparse, leading to potential oversights by inexperienced pathologists.
  • Recognizing this differentiation is vital not only for establishing a correct diagnosis and preventing the false reporting of rare tumors but also because it influences the classification of the cancer as high-grade, impacting patient treatment and management.
  • A case study of a male patient revealed a high-grade urothelial carcinoma with features resembling primarily colonic-type adenocarcinoma, showcasing the importance of identifying divergent differentiation to rule out metastasis from other organs.
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Renal leiomyomas are rare benign mesenchymal tumors that arise from the smooth muscle cells in the renal capsule, renal pelvis, and the smooth muscles of vessels in the kidney. They are usually found by accident during autopsies or on different imaging modalities made on other occasions. The clinical presentation may include hematuria and abdominal or flank pain, although renal leiomyomas are most frequently asymptomatic.

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Nephrogenic adenomas are benign lesions that develop within the urinary tract. Most often developing within the urinary bladder, these lesions have a debatable etiopathogenesis, with hamartoma, rest hyperplasia, and transplantation of renal tubular cells being the most widely accepted ones. Nephrogenic adenomas develop more often in adult males, and predisposing factors for their development are prior urinary system injury, infection, or malignancy, with a subset of cases developing in renal transplant patients.

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Malaria is an infectious disease caused by several types of parasitic plasmodia and transmitted to humans through Anopheles mosquitoes. The disease has long been widespread and has caused a significant number of deaths and decreased life quality from sequelae worldwide. As understanding of the disease increased immensely at the beginning of the 20th century, eradication plans were implemented to decrease disease transmission.

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Human papillomaviruses (HPV) are a big group of infection agents with oncogenic potential, especially regarding squamous epithelium. Some high-risk variants are key in the development of squamous cell carcinomas (SCC) across multiple systems, the most affected of which is the female reproductive system, but also parts of the gastrointestinal tract, head, and neck SCC, and cutaneous and pulmonary (bronchogenic) SCCs. In cases where a patient develops two SCCs in different systems, often the main question is whether these tumors are synchronous, metachronous, or if one of the tumors is a metastasis from the other, with HPV testing and stereotype identification often being of aid in differentiating between these.

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Cauda equina neuroendocrine tumors (CENET) are rare neoplastic processes that develop in the cauda equina or filum terminale region of the spinal cord, which in previous incarnations of the World Health Organization (WHO) classification of the central nervous system (CNS) tumors were designated as paragangliomas. The change of terminology was carried out due to the rarity of the condition, its specific place of origin, the non-specific clinical and imaging characteristics with which the tumors present, and differences in biological properties (secretion and progression) as well as some minor differences in immunohistochemical protein expression patterns. Herein, we present a case of a male patient in his sixties who presented to us for a histopathological consultation of a previously excised tumor, which was grossly well-demarcated and connected to a nerve root in the cauda equina region.

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Renal oncopathology in adults, as a field of pathology, is dominated by a single entity - clear cell renal cell carcinoma (RCC) with other entries, such as urothelial carcinoma of the renal pelvis, angiosarcoma, and others being extremely rare. Herein, we report two histopathological cases with differential diagnoses of spindle cell renal neoplasms. The first patient, a 42-year-old male, presented with new-onset right-sided abdominal flank pain, and imaging showed a 12 cm renal tumor.

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Background One of the most characteristic features of non-invasive urothelial carcinoma (UC) is its high recurrence rate. Guanine-adenine-thymine-adenine nucleotide sequence-binding protein 3 (GATA3), as a transcription factor, correlates with urothelial differentiation and has been reported with poor prognosis in high-grade UC and recurrence in breast malignancies. As such, we set out to study the specifics of GATA3 in non-invasive UC, emphasizing on prediction for recurrence.

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Zbtb20 (zinc finger and BTB domain-containing protein 20) is a transcription factor with a zinc finger DNA binding domain and a BTB domain responsible for protein-protein interaction. Recently, this TF has received attention because new data showed its pivotal involvement in normal neural development and its regulatory effects on proliferation and differentiation in different tissues. Zbtb20 was shown to increase proliferation and migration and confer resistance to apoptosis in the contexts of many malignant tumors like hepatocellular carcinoma, non-small-cell lung carcinoma, gastric adenocarcinoma, glioblastoma multiforme, breast cancer, and acute myeloid leukemia.

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somatic variants are predictors of resistance to anti-EGFR therapy for colorectal cancer (CRC) and affect the outcome of the disease. Our study aimed to evaluate the frequency of , with a focus on variants, and their association with tumor location and some clinicopathological characteristics in Bulgarian CRC patients. We prospectively investigated 236 patients with advanced and metastatic CRC.

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Healthcare in Bulgaria is a universal and free right as per legislation. However, due to limited government funding from a singular state-run insurance fund and the inequities in the distribution of limited healthcare professionals, access to quality healthcare is difficult for most citizens. Pathology is one of the most severely affected specialties as it is not only regarded as one of the most difficult ones due to its aspects and difficulties in obtaining it but also due to the lack of funding.

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Introduction SARS-CoV-2 is an epitheliotropic viral agent with epithelial tropism. Although the clinical significance and severity of affection is the most pronounced in the respiratory system, other organs and systems are also infected and, hence affected, such as the central nervous system, gastrointestinal tract, cardiovascular, and urinary systems. Herein, we set out to evaluate the presence and degree of morphological changes within the renal parenchyma and its relation to disease outcome.

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Adenocarcinomas of the urinary bladder are exceedingly rare and present in various morphological forms. Virtually all of these are identical to glandular malignant neoplasia native to topographically neighboring organs, where the incidence of adenocarcinoma is also much more common, such as the large intestine. Cases of glandular malignancies of the urinary bladder, therefore, require not only a detailed histopathological evaluation and interpretation but also a detailed clinical and radiological one.

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Glioblastoma (GBM) is a central nervous system (CNS) high-grade glioma with a dismal patient prognosis. Classical concepts surrounding GBM development and progression indicate its ability to produce metastasis within the CNS, one of the few primary tumors with such capabilities. While classical concepts state that no primary CNS tumor produces extracranial metastasis, there have been multiple reports of such occurrences over the previous two decades.

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Henoch-Schönlein purpura (HSP) is the most common vasculitis in childhood, presenting with purpura, predominantly of the lower extremities and occasionally with renal involvement as well. Although associated with childhood, HSP, although rarely, can also develop in adults as well. Here we present a patient in his sixties, presenting with a myriad of rash units on his lower extremities, including bullous ones, and a constellation of chronic kidney failure.

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Introduction Urothelial carcinomas represent a distinct group of malignancies with a high recurrence potential. Multiple studies have established a set of interactions between the tumor cells of urothelial neoplasms and the extracellular matrix regarding invasion and tumor progression. In the present study, we evaluated the expression of fibroblast growth factor-2 (FGF2) in early-stage urothelial carcinomas of the urinary bladder (pTa and pT1) regarding the invasive potential of these tumors.

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Pleomorphic xanthoastrocytoma (PXA) is a rare central nervous system malignant neoplasm with a relatively favorable prognosis. As PXA histologically presents with large, multinucleated neoplastic cells, its principal differential diagnosis is giant cell glioblastoma (GCGBM). While there is a significant overlap between the two histologically and the neuropathological diagnosis can be challenging, as well as having some overlap neuroradiologically, the patient prognosis differs significantly, with PXA having a more favorable one.

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Dysembryoplastic neuroepithelial tumors (DNTs) are rare neoplastic entries of the central nervous system. Conventionally DNTs are with cortical location and predominantly occur in the temporal lobe associated with epilepsy. Subtentorial DNTs are rare entries.

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Background Cardiovascular disease (CVD) is still the leading cause of death globally. Alterations in the arterial wall architecture predict CVD morbidity and mortality and are associated with other CVD risk factors. Aortic wall thickness is closely linked to short- and long-term CVD morbidity and mortality, even without pronounced atherosclerotic changes.

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Leiomyosarcomas are rare malignant mesenchymal neoplasms originating from smooth muscle cells. Although leiomyosarcoma is commonly located in the female reproductive system, gastrointestinal tract, and subcutaneous tissues, it is a rare entry in the head and neck area, probably due to the scarcity of smooth muscle tissue in this topographical region. Herein we present a histopathological case report of a 60-year-old male with a slow-growing painless mass on the middle third of the right lateral lingual margin, with focal ulceration measuring 1x1.

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Myeloproliferative neoplasms (MPN) are clonal disorders of hematopoietic stem cells with a proliferation of one or more myeloid lineage and mature cell overproduction, while myelodysplastic syndrome (MDS)/MPN simultaneously show aspects of MDS and MPN, leading to partially ineffective hematopoiesis with associated dysplastic changes. This spectrum of disorders includes chronic myeloid leukemia, polycythemia vera, primary myelofibrosis, and essential thrombocythemia. MDS/MPN are classically not associated with renal complications; however, an accumulating body of evidence suggests that multiple growth factors, cytokines, endothelial damage, and an activated complement system in these patients can induce glomerulopathy, as nearly a third of these patients present with advanced renal disease on diagnosis, which is unlikely to be age or hypertension-related.

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Introduction Several clinical peculiarities mark urothelial carcinomas and their biological behavior. Key in these are its relatively indolent course before manifestation and its high recurrence rate. So far, no biomarker has been identified as a predictor for these factors.

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Silver impregnation methods are essential in biopsy interpretation in nephropathology with regard to visualizing the basal lamina and its associated changes. The most widely used methods, mainly Jones methenamine impregnation, are time-consuming in their protocols and require multiple microscopy control points. In this report, we propose an alternative, modified method for silver impregnation with methenamine solution with a significantly shorter protocol time and good staining quality, allowing for proper interpretation of basal lamina changes in the glomeruli and blood vessels.

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Diffuse astrocytic gliomas and their most common and aggressive representation, glioblastoma (GBM), which as per the 2021 World Health Organization (WHO) guidelines is an isocitrate dehydrogenase (IDH) wildtype without alteration in histone 3 and has glomeruloid vascular proliferation, tumor necrosis, telomerase reverse transcriptase (TERT) promoter mutation, epidermal growth factor receptor (EGFR) gene amplification, or +7/-10 chromosome copy-number changes, are fast-growing tumors with a dismal patient prognosis. Herein, we present cases of a 63-year-old male who, despite no evidence of tumor growth, developed a 6-cm tumor, histologically verified as GBM, WHO CNS grade 4, within eight months, and a 74-year-old female in whom a 1.5-cm tumor grew to 43 mm within 28 days, once again histologically confirmed as GBM, WHO CNS grade 4.

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Light chain deposition disease (LCDD) is a rare condition associated with the overproduction and deposition of monoclonal light chain immunoglobulins. The kidneys are universally affected in LCDD, with the development of renal failure with nephrotic syndrome, microscopic hematuria, and proteinuria. Most cases are associated with a plasma cell neoplasm (multiple myeloma or plasmacytoma) or other lymphoproliferative disorders, with a reasonable number of cases also being idiopathic.

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