Deyan Dzhenkov

Dr. Deyan Dzhenkov

orcid

Research Focus & Metrics

Academic Career Length

13Years (2014-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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31 January 2018 in Medical Oncology
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GSGeorge Stoyanov Stoyanov
George Stoyanov Stoyanov
DDDeyan Dzhenkov
Deyan Dzhenkov
PGPeter Ghenev
Peter Ghenev
BIBogomil Iliev
Bogomil Iliev
YEYavor Enchev
Yavor Enchev
ATAnton B. Tonchev
Anton B. Tonchev

1 March 2018 in Folia Medica
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GSGeorge Stoyanov Stoyanov
George Stoyanov Stoyanov
DDDeyan Dzhenkov
Deyan Dzhenkov
Glioblastoma multiforme(GBM) is a grade IV WHO malignant tumor with astrocytic differentiation. As one of the most common clinically diagnosed central nervous system (CNS) oncological entries, there have been a wide variety of historical reports of the description and evolution of ideas regarding these tumors.The first recorded reports of gliomas were given in British scientific reports, by Berns in 1800 and in 1804 by Abernety, with the first comprehensive histomorphological description being given in 1865 by Rudolf Virchow. In 1926 Percival Bailey and Harvey Cushing gave the base for the modern classification of gliomas. Between 1934 and 1941 the most prolific researcher in glioma research was Hans-Joachim Scherer, who postulated some of the clinico-morphological aspects of GBM. With the introduction of molecular and genetic tests the true multifomity of GBM has been established, with different genotypes bearing the same histomorphological and IHC picture, as well as some of the aspects of gliomagenesis. For a GBM to develop, a specific trigger mutation needs to occur in a GBM stem cell – primary GBM, or a slow aggregation of individual mutations, without a distinct trigger mutation – secondary GBM.Knowledge of GBM has been closely related to general medical knowledge of the CNS since these malignancies were first described more than 200 years ago. Several great leaps have been made in that time, in the footsteps of both CNS and advancements in general medical knowledge.

1 February 2022 in Cureus
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GSGeorge Stoyanov Stoyanov
George Stoyanov Stoyanov
ELEmran Lyutfi
Emran Lyutfi
RGReneta Georgieva
Reneta Georgieva
RGRadoslav Georgiev
Radoslav Georgiev
DDDeyan Dzhenkov
Deyan Dzhenkov
PGPeter Ghenev
Peter Ghenev
The 2021 World Health Organization (WHO) classification of tumors of the central nervous system (CNS) has introduced significant changes to tumor taxonomy. One of the most significant changes in the isolation of isocitrate dehydrogenase (IDH) mutant forms of glioblastoma multiforme (GBM) into separate entities, as well as no longer allowing for entries to be classified as not otherwise specified (NOS). As a result, this entity now includes only the most aggressive adult-type tumors. As such, established prognostic factors no longer apply, as they now form the criteria of different disease entries or have been established based on a mixed cohort. Herein, we aimed to reclassify glioblastoma cases diagnosed per the 2016 WHO tumors of the CNS classification into the 2021 WHO tumors of the CNS classification and establish a patient survival pattern based on age, gender, tumor location, and size as well as tumor O‐6‐methylguanine‐DNA methyltransferase (MGMT) mutation. A retrospective, non-clinical approach was utilized. Biopsy specimens of adults diagnosed with GBM, WHO grade 4, NOS in the period February 2018-February 2021 were reevaluated. The data regarding the patient's gender and age were withdrawn from the medical documentation. Immunohistochemistry was performed with mouse monoclonal anti-IDH R132H and rabbit polyclonal anti-MGMT. Radiology data on tumor location and size were pulled from the radiology repository. Data were statistically analyzed for significance, using Kaplan-Meier survival analysis, with a 95% confidence interval and p<0.05 defined as significant. A total of 58 cases fit the set criteria, with eight of them (13.7%) harboring an IDH R132H mutation and were hence reclassified as diffuse astrocytoma IDH-mutant, WHO CNS grade 4. The cases that retained their GBM classification included n=28 males and n=22 females, a male to female ratio of 1.27:1, and a mean age of 65.3 years (range 43-86 years). The MGMT mutational status revealed a total of n=17 positive cases (35%), while the remaining cases were negative. No hemispheric predilection could be established. Lobar predilection was as follows: temporal (37.78%), parietal (28.89%), frontal (24.44%), and occipital (8.89%). The mean tumor size measured on neuroradiology across the cohort was 50.51 mm (range 20-76 mm). The median survival across cases was 255.96 days (8.41 months), with a range of 18-1150 days (0.59-37.78 months). No statistical correlation could be established between patient survival and gender, hemispheric location, lobar location, and tumor size. A significant difference in survival was established only when comparing the 41-50 age groups to the 71-80 and 81-90 age groups and MGMT positive versus negative tumors (p=0.0001). From a practical standpoint, the changes implemented in the new classification of CNS tumors define GBM as the most aggressive adult type of tumor. Based on their significantly more favorable prognosis, the reclassification of IDH mutant forms of astrocytomas has had little epidemiological impact on this relatively common malignancy but has significantly underlined the dismal prognosis. The changes have also led to MGMT promoter methylation status being the only significant prognostic factor for patient survival in clinical use, based on its prediction for response to temozolomide therapy in this nosological unit clinically presenting when it has already reached immense size.

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Stoyan KostovStoyan Kostov
Stoyan Kostov
SSStanislav Slavchev
Stanislav Slavchev
DDDeyan Dzhenkov
Deyan Dzhenkov
DMDimitar Mitev
Dimitar Mitev
angel yordanovangel yordanov
angel yordanov
The term “spaces” refers to the areas delimited by at least two independent fasciae and filled with areolar connective tissue. However, there is discrepancy regarding the spaces and their limits between clinical anatomy and gynecologic surgery, as not every avascular space described in literature is delimited by at least two fasciae. Moreover, new spaces and surgical planes have been developed after the adoption of laparoscopy and nerve-sparing gynecological procedures. Avascular spaces are useful anatomical landmarks in retroperitoneal anatomic and pelvic surgery for both malignant and benign conditions. A noteworthy fact is that for various gynecological diseases, there are different approaches to the avascular spaces of the female pelvis. This is a significant difference, which is best demonstrated by dissection of these spaces for gynecological, urogynecological, and oncogynecological operations. Thorough knowledge regarding pelvic anatomy of these spaces is vital to minimize morbidity and mortality. In this article, we defined nine avascular female pelvic spaces—their boundaries, different approaches, attention during dissection, and applications in obstetrics and gynecology. We described the fourth space and separate the paravesical and pararectal space, as nerve-sparing gynecological procedures request a precise understanding of retroperitoneal spaces.

2 July 2017 in Cureus
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GSGeorge Stoyanov Stoyanov
George Stoyanov Stoyanov
MKMartina Kitanova
Martina Kitanova
DDDeyan Dzhenkov
Deyan Dzhenkov
PGPeter Ghenev
Peter Ghenev
NSNikolay Sapundzhiev
Nikolay Sapundzhiev
Head and neck cancer (HNC) comprises a diverse group of oncological entities, originating from various tissue types and organ localizations, situated in the topographical regions of the head and neck (H&N). This single institution retrospective study was aimed at establishing the HNC patient demographics and categorizing the individual incidence of H&N malignancies, regarding their organ of origin and main histopathological type. All histologically verified cases of HNC from a single tertiary referral center were reviewed in a descriptive retrospective manner. Data sampling period was 47 months. Male to female ratio of the registered HNC cases was 3.24:1. The mean age of diagnosis was 63.84 ± 12.65 years, median 65 years. The most common HNC locations include the larynx 30.37% (n = 188), lips and oral cavity 29.08% (n = 180), pharynx 20.03% (n = 124) and salivary glands 10.94% (n = 68), with other locations such as the external nose, nasal cavity and sinuses and auricle and external ear canal harboring a minority of the cases. The main histopathological groups include squamous cell carcinoma 76.74% (n = 475) and adenocarcinoma 6.14% (n = 38), with other malignant entries such as other epithelial malignancies, primary tonsillar, mucosa-associated lymphoid tissue or parenchymal lymphomas, connective tissue neoplasias, neuroendocrine and vascular malignancies diagnosed in a minority of cases. Considered to be relatively rare, HNC represents a diverse group of oncological entities with individual and specific demographic characteristics. The reported single institution results appear representative of the national incidence and characteristics of HNC.

22 November 2021 in Clinics and Practice
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Stoyan KostovStoyan Kostov
Stoyan Kostov
YKYavor Kornovski
Yavor Kornovski
VIVesela Ivanova
Vesela Ivanova
DDDeyan Dzhenkov
Deyan Dzhenkov
DMDimitar Metodiev
Dimitar Metodiev
angel yordanovangel yordanov
angel yordanov
Sarcomas of the uterine corpus are rare malignant neoplasms, which are further classified into mesenchymal tumors, and mixed (epithelial plus mesenchymal) tumors. The main issues concerning these neoplasms are the small number of clinical trials, insufficient data from evidence-based medicine, insignificant interest from the pharmaceutical industry, all of which close a vicious circle. The low frequency of these malignancies implies insufficient experience in the diagnosis, hence incomplete surgical and complex treatment. Additionally, the rarity of these sarcomas makes it very difficult to develop clinical practice guidelines. Preoperative diagnosis, neoadjuvant and adjuvant chemoradiation, target and hormone therapies still raise many controversies. Disagreements about the role and type of surgical treatment are also often observed in medical literature. There are still insufficient data about the role of pelvic lymph node dissection and fertility-sparing surgery. Pathologists’ experience is of paramount importance for an accurate diagnosis. Additionally, genetics examinations become part of diagnosis in some sarcomas of the uterine corpus. Some gene mutations observed in uterine sarcomas are associated with different outcomes. Therefore, a development of molecular classification of uterine sarcomas should be considered in the future. In this review, we focus on the epidemiology, pathogenesis, pathology, diagnosis and treatment of the following sarcomas of the uterine corpus: leiomyosarcoma, low- and high-grade endometrial stromal sarcomas, undifferentiated sarcoma and adenosarcoma. Uterine carcinosarcomas are excluded as they represent an epithelial tumor rather than a true sarcoma.