Blastic plasmacytoid dendritic cell neoplasm:Two case reports

BACKGROUND Blastic plasmacytoid dendritic cell tumor(BPDCN)is a rare and highly invasive lymphohematopoietic tumor that originates from plasmacytoid dendritic cells.BPDCN has an extremely poor prognosis.Skin lesions are usually the first manifestation of BPDCN,although the tumor may also invade the bone marrow,lymph nodes,peripheral blood,and other parts of the body,leading to several other manifestations,requiring further differentiation through skin biopsy and immunohistochemistry.CASE SUMMARY In the present paper,the cases of 2 patients diagnosed with BPDCN are discussed.The immunohistochemistry analysis of these 2 patients revealed positivity for CD4,CD56,and CD123.Currently,no standard chemotherapy regimen is available for BPDCN.Therefore,intensive therapy for acute lymphoblastic leukemia was applied as the treatment method for these 2 cases.CONCLUSION Although allogeneic bone marrow transplantation could be further effective in prolonging the median survival the ultimate prognosis was unfavorable.Future treatment modalities tailored for elderly patients will help prolong survival.

Advancing the understanding and management of blastic plasmacytoid dendritic cell neoplasm:Insights from recent case studies

We specifically discuss the mechanisms of the pathogenesis,diagnosis,and management of blastic plasmacytoid dendritic cell neoplasm(BPDCN),a rare but aggressive haematologic malignancy characterized by frequent skin manifestations and systemic dissemination.The article enriches our understanding of BPDCN through detailed case reports showing the clinical,immunophenotypic,and histopathological features that are critical for diagnosing this disease.These cases highlight the essential role of pathologists in employing advanced immunophenotyping techniques to accurately identify the disease early in its course and guide treatment decisions.Furthermore,we explore the implications of these findings for management strategies,emphasizing the use of targeted therapies such as tagraxofusp and the potential of allogeneic haematopoietic stem cell transplantation in achieving remission.The editorial underscores the importance of interdisciplinary approaches in managing BPDCN,pointing towards a future where precision medicine could significantly improve patient outcomes.

Azacitidine maintenance therapy for blastic plasmacytoid dendritic cell neoplasm allograft: A case report

BACKGROUND Blastic plasmacytoid dendritic cell neoplasm(BPDCN)is a rare,highly invasive malignant neoplasm.There is no universally accepted standard of care because of its rarity and the dearth of prospective research.It is still challenging for some patients to achieve persistent clinical remission or cure,despite the success of allogeneic hematopoietic stem cell transplantation(allo-HSCT),indicating that there is still a significant recurrence rate.We report a case of prevention of BPDCN allograft recurrence by azacitidine maintenance therapy and review the relevant literature.CASE SUMMARY We report a 41-year-old man with BPDCN who was admitted to hospital due to skin sclerosis for>5 mo’duration.BPDCN was diagnosed by combined clinical assessment and laboratory examinations.Following diagnosis,the patients underwent induction consolidation chemotherapy to achieve the first complete remission,followed by bridging allo-HSCT.Post-transplantation,azacitidine(75 mg/m2 for 7 d)was administered as maintenance therapy,with repeat administration every 4–6 wk and appropriate extension of the chemotherapy cycle.After 10 cycles,the patient has been disease free for 26 mo after transplantation.Regular assessments of bone marrow morphology,minimal residual disease,full donor chimerism,Epstein–Barr virus,and cytomegalovirus all yielded normal results with no abnormalities detected.CONCLUSION Azacitidine may be a safe and effective maintenance treatment for BPDCN following transplantation because there were no overt adverse events during the course of treatment.

Blastic plasmacytoid dendritic cell neoplasm in Jinhua,China:Two case reports

BACKGROUND Blastic plasmacytoid dendritic cell neoplasm(BPDCN)is a rare and clinically aggressive hematologic malignancy originating from the precursors of plasmacytoid dendritic cells.BPDCN often involves the skin,lymph nodes,and bone marrow,with rapid clinical progression and a poor prognosis.The BPDCN diagnosis is mainly based on the immunophenotype.CASE SUMMARY In this paper,we retrospectively analyzed 2 cases of BPDCN.Both patients were elderly males.The lesions manifested as skin masses.Morphological manifestations included diffuse and dense tumor cell infiltration of the dermis and subcutaneous tissues.Immunohistochemistry staining showed that cluster of differentiation CD4,CD56,CD43,and CD123 were positive.CONCLUSION In this paper,we retrospectively analyzed 2 cases of BPDCN.Both patients were elderly males.The lesions manifested as skin masses.Morphological manifestations included diffuse and dense tumor cell infiltration of the dermis and subcutaneous tissues.Immunohistochemistry staining showed that cluster of differentiation CD4,CD56,CD43,and CD123 were positive.

Blastic Plasmacytoid Dendritic Cell Neoplasm:Progress in Cell Origin,Molecular Biology,Diagnostic Criteria and Therapeutic Approaches

Blastic plasmacytoid dendritic cell neoplasm(BPDCN)is a rare hematological malignancy characterized by recurrent skin nodules,an aggressive clinical course with rapid involvement of hematological organs,and a poor prognosis with poor overall survival.BPDCN is derived from plasmacytoid dendritic cells(pDCs)and its pathogenesis is unclear.The tumor cells show aberrant expression of CD4,CD56,interleukin-3 receptor alpha chain(CD 123),blood dendritic cell antigen 2(BDCA 2/CD303),blood dendritic cell antigen 4(BDCA4)and transcription factor(E protein)E2-2(TCF4).The best treatment drugs are based on experience by adopting those used for either leukemia or lymphoma.Relapse with drug resistance generally occurs quickly.Stem cell transplantation after the first complete remission is recommended and tagraxofusp is the first targeted therapy.In this review,we summarize the differentiation of BPDCN from its cell origin,its connection with normal pDCs,clinical characteristics,genetic mutations and advances in treatment of BPDCN.This review provides insights into the mechanisms of and new therapeutic approaches for BPDCN.

Effects of Antisense Oligodeoxynucleotide to Follicle-stimulating Hormone Receptor on the Cell Proliferation and Apoptosis in Cells Derived from Human Ovarian Mucinous Cystadenocarcinoma in Vitro

The human ovarian mucinous cystadenocarcinoma （hOMC） cells were co-cultured with antisense oligodeoxynucleotide （antisense ODN）, nonsense ODN, and follicle-stimulating hormone （FSH） at different concentrations for the purpose of observing the effects of antisense ODN to FSH receptor （FSHR） on the proliferation and apoptosis of cultured hOMC cells in vitro. The inhibitory rates of growth were measured by using MTT method on the 2nd, 4th, 6th, 8th and 10th days after the interference of antisense ODN, nonsense ODN, and FSH, respectively. The apoptotic rates and the cell cycles were determined by means of flow cytometry, the apoptosis indexes were detected by using TUNEL, and the expression of caspase-3 was measured by using SP immunohistochemistry. Compared with that in the control group, the proliferative activity of hOMC cells was increased obviously in FSH groups （P〈0.05 or P〈0.01）, decreased distinctly in antisense ODN groups （P〈0.05 or P〈0.01）, and unchanged in nonsense ODN groups, respectively. Meanwhile, antisense ODN could significantly antagonize the FSH-promoted cell proliferative activity （P〈0.01）. Compared with those in the control group, the apoptotic rates and the expression of caspase-3 were dramatically increased in the mid- and high-dose antisense ODN groups （P〈0.05 or P〈0.01）, while the number of cells in G1/G0 phase was significantly decreased and that in S phase distinctly increased （P〈0.01）, There was no change in nonsense ODN groups （P〉0.05）, It was suggested that FSH may improve the development of hOMC cells, However, antisense ODN could inhibit proliferative activity and the FSH-promoted proliferative activity in hOMC cells, at the same time, antisense ODN could inhibit hOMC cell growth by inducing apoptosis.

Human ovarian neoplasm cell CD147 stimulates production and activation of matrix metalloproteinases in co-cultures with mouse fibroblasts

Objective: To investigate the expression of CD147 on human ovarian neoplasm cell lines and its influence on production and activation of matrix metallproteinases(MMPs). Methods: The expression of CD147 on different human ovarian neoplasm cell lines was studied by western blotting. Co-culture was carried out to investigate the stimulative effect of the positive expression CD147 cell HO-8910 on the production of MMPs of fibroblast cell in vitro. Zymography and immune blotting were used to study the production and activity of positive MMPs, at the time, to explore the relation between CD147 and MMPs. Results: CD147 was positively presented in 2 ovarian neoplasm cell lines(HO-8910,3-AO), but in SKOV3, TC-1,NIN3T3 cell was negative. MMP-2 and MMP-9 were detected by HO-8910 cell line, mouse fibroblast cell and co-culture cells; but the expression in co-culture cell is obviously higher than individual cultures of each type alone.CD147 stimulated MMPs in dose-dependent manner. Conclusion: CD147 causes increased production and activation of MMP-2, MMP-9.CD147 is probably a indirect marker of some ovarian cancer cells with invasion and metastasis.

Blastic plasmacytoid dendritic cell neoplasm with skin and bone marrow involvement: Report of three cases

BACKGROUND Blastic plasmacytoid dendritic cell neoplasm(BPDCN)is a rare and highly aggressive hematopoietic malignancy.BPDCN is difficult to diagnose because of the overlap in morphologic and immunophenotypic features with various cutaneous lymphatic hematopoietic tumors.CASE SUMMARY We report on three BPDCN cases,all characterized by skin nodules and examined by histology,immunohistochemical detection,in situ hybridization for Epstein-Barr virus,and follow-up.We also review the relevant literature.All patients were positive for CD56 and negative for Epstein-Barr encoded small RNA.Two patients had bone marrow involvement.Chemotherapy is the main treatment for BPDCN,but case 1 showed bone marrow suppression and case 2 developed recurrence after chemotherapy.Case 1 survived for 7 mo,case 2 for 17 mo,and case 3 for 9 mo.CONCLUSION An accurate pathological diagnosis is a precondition for treatment,and the diagnosis of BPDCN should be based on a combination of clinical symptoms,pathological characteristics,immunophenotype,and other auxiliary examinations.It is necessary to clarify the clinicopathological features and biological behavior of BPDCN to improve its understanding by both clinicians and pathologists.Case 2 survived significantly longer than the other two cases,suggesting that the treatment received by case 2 was more effective.

Retroperitoneal neoplasm with perivascular epithelioid cell differentiation: A case report and review of literature

The retroperitoneal neoplasm with perivascular epithelioid cell differentiation (PEComa) is an extremely rare pathological entity. In this article, we reported one case of a 45-year-old woman who was admitted to our hospital (The Second People's Hospital of Hefei, China) for retroperitoneal neoplasm with perivascular epithelioid cell differentiation. The B ultrasonic examination showed echopoor in the region of cavitas pelvis. The histologic characteristics and immunohistochemical phenotype both revealed the neoplasm with perivascular epithelioid cell differentiation.

Perivascular epithelioid cell tumors of the liver misdiagnosed as hepatocellular carcinoma:Three case reports

BACKGROUND Hepatic perivascular epithelioid cell neoplasms(PEComas)are rare.Diagnostic and treatment experience with hepatic PEComa remains insufficient.CASE SUMMARY Three hepatic PEComa cases are reported in this paper:One case of primary malignant hepatic PEComa,one case of benign hepatic PEComa,and one case of hepatic PEComa with an ovarian mature cystic teratoma.During preoperative imaging and pathological assessment of intraoperative frozen samples,patients were diagnosed with hepatocellular carcinoma(HCC),while postoperative pathology and immunohistochemistry subsequently revealed hepatic PEComa.Patients with hepatic PEComa which is misdiagnosed as HCC often require a wider surgical resection.It is easy to mistake them for distant metastases of hepatic PEComa and misdiagnosed as HCC,especially when it’s combined with tumors in other organs.Three patients eventually underwent partial hepatectomy.After 1-4 years of follow-up,none of the patients experienced recurrence or metastases.CONCLUSION A clear preoperative diagnosis of hepatic PEComa can reduce the scope of resection and prevent unnecessary injuries during surgery.

Diagnosis and treatment of primary seminoma of the prostate:A case report and review of literature

BACKGROUND Primary seminoma of the prostate(PSP)is a rare type of extragonadal germ cell tumour that is easily misdiagnosed,owing to the lack of specific clinical features.It is therefore necessary for clinicians to work toward improving the accuracy of PSP diagnosis.CASE SUMMARY A 59-year-old male patient presenting with acute urinary retention was admitted to a local hospital.A misdiagnosis of benign prostatic hyperplasia led to an improper prostatectomy.Histopathology revealed PSP invading the bladder neck and bilateral seminal vesicles.Further radiotherapy treatment for the local lesion was performed,and the patient had a disease-free survival period of 96 mo.This case was analysed along with 13 other cases of PSP identified from the literature.Only four of the cases(28.6%)were initially confirmed by prostate biopsy.In these cases,imaging examinations showed an enlarged prostate(range 6-11 cm)involving the bladder neck(13/14).Of the 14 total cases,11(78.6%)presented typical pure seminoma cell features,staining strongly positive for placental alkaline phosphatase,CD117,and OCT4.The median age at diagnosis was 51(range 27-59)years,and patients had a median progression-free survival time of 48(range 6-156)mo after treatment by cisplatin-based chemotherapy combined with surgery or radiotherapy.The remaining three were cases of mixed embryonal tumours with focal seminoma,which had clinical features similar to those of pure PSP,in addition that they also had elevated serum alpha fetoprotein,beta-human chorionic gonadotropin,and lactose dehydrogenase.CONCLUSION PSP should be considered in patients younger than 60 years with an enlarged prostate invading the bladder neck.Further prostate biopsies may aid in proper PSP diagnosis.Cisplatin-based chemotherapy is still the main primary therapy for PSP.

The Prognostic Value of Pathological and Molecular Margins Marked by p53 and eIF4E in Laryngeal Carcinoma

Objective: To study the prognostic value of the pathological margin and molecular margin marked by eIF4E and P53 protein in laryngeal carcinoma. Methods: The prognostic value of pathological and molecular margin was studied in 253 cases and 67 cases respectively, the latter were pathological negative margin chosen from the former. Immunohistochemisty was used to detect the expression of eIF4E and p53 proteins. Results: The rate of pathological, p53 and eIF4E positive margins was 20.2%, 19.4% and 32.8% respectively. The recurrent rate of those with positive margins was higher than that of negative margins, which including pathological margin (70.6% vs 35.1%, P =0.0000), p53 margin (69.2% vs 33.3%, P =0.018) and eIF4E margin (63.6% vs 28.9%, P =0.018); The survival rate of those with negative margins was higher than those with positive margins, including pathological margin (the 5-year cumulative survival rate was 37.52% and 64.37% respectively, P =0.0023), p53 margin (the 5-year cumulative survival rate was 24.62% and 75.69% respectively, P =0.0012) and eIF4E margin (the 5-year cumulative survival rate was 43.31% and 77.52% respectively, P =0.0006). Conclusion: The prognosis of those with both pathological and molecular positive margins was worse than that of the negative margins; Both the eIF4E and p53 were useful markers to pick out the poor prognostic patients from those with pathological negative margin, and the former seemed to be more potential.

Clinical Course Of Patients with Small Cell Lung Cancer As Second Primary Malignancy

Objective： To evaluate the clinical course of patients with small cell lung cancer （SCLC） as second primary malignancy. Methods： Among the 355 patients diagnosed with SCLC at Helen and Harry Gray Cancer Center of Hartford Hospital Connecticut USA between 1988 and 1998, the records of 48 patients, which had been diagnosed with other malignancies before their diagnosis of SCLC, were retro- spectively reviewed. Results： Forty-eight patients （13.5%） were diagnosed with other malignancies prior to their SCLC among which 43 had documented smoking history and 93% of them （40/43） were current/former smokers. Of the 28-second primary SCLC patients who were treated with standard method, 11 （39.3%） achieved CR. 12 （42.8%） achieved PR, and the RR was 82.1%. The median survival of the 28 treated with standard method was 11.3 months （5.1-77.7 months）, while that of the rest 19 untreated patients （1 of 20 was lost to follow-up） was only 2.0 months （0.5 34.0 months）. There was no significant difference in the median survival and RR between 165 treated first primary SCLC （13.5 months and 77.6% respectively） and 28 treated secondary primary SCLC （11.3 months and 82.1% respectively） （P〉0.05）. The patients who had prostate cancer were older and subjected to less treatments than those with skin cancer, so their survival was shorter than the latter （3.5 months vs. 15 months, P〈0.05）. Conclusion： The response and survival of the treated patients with SCLC as a second malignancy showed no difference as compared to the treated ones with SCLC only. Therefore, an active medical treatment is important to relieve symptom and prolong survival of the second primary SCLC patients.

Multimodality treatment in hepatocellular carcinoma patients with tumor thrombi in portal vein

AIM: To compare the therapeutic effect and significances of multimodality treatment for hepatocellular carcinoma (HCC) with tumor thrombi in portal vein (PVTT). METHODS: HCC patients (n=147) with tumor thrombi in the main portal vein or the first branch of portal vein were divided into four groups by the several therapeutic methods. There were conservative treatment group in 18 out of patients (group A); and hepatic artery ligation(HAL) and/or hepatic artery infusion (HAI) group in 18 patients (group B), in whom postoperative chemoembolization was done periodically; group of removal of HCC with PVTT in 79 (group C) and group of transcatheter hepatic arterial chemoembolization (TACE) or HAI and/or portal vein infusion (PVI) after operation in 32 (group D). RESULTS: The median survival period was 12 months in our series and the 1-,3-, and 5-year survival rates were 44.3%, 24.5% and 15.2%, respectively. The median survival times were 2, 5, 12 and 16 months in group A, B, C and D, respectively. The 1-, 3- and 5-year survival rates were 5.6%, 0% and 0% in group A; 22.2%, 5.6% and 0% in group B; 53.9%, 26.9% and 16.6% in group C; 79.3%, 38.9% and 26.8% in group D, respectively. Significant difference appeared in the survival rates among the groups (P 【 0.05). CONCLUSION: Hepatic resection with removal of tumor thrombi and HCC should increase the curative effects and be encouraged for the prolongation of life span and quality of life for HCC patients with PVTT, whereas the best therapeutic method for HCC with PVTT is with regional hepatic chemotherapy or chemoembolization after hepatic resection with removal of tumor thrombi.

Extramedullary plasmocytoma associated with a massive deposit of amyloid in the duodenum

We report a rare case of extramedullary plasmocytoma associated with a massive deposit of amyloid in the duodenum. A 72-year-old Japanese man was admitted to our hospital presenting with a 3-mo history of epigastric pain, vomiting and weight loss. On computed tomography （CT） a wall thickening of the fourth part of the duodenum was observed. Multiple biopsies obtained from the lesion showed infiltration of plasma cells and lymphocytes, but they were not conclusive. The patient underwent resection of the lesion and, on histopathological examination, the lesion consisted of a dense and diffuse infiltrate of plasma cells and a few admixed lymphocytes with reactive follicles extending to the muscular propria. An extensive deposition of amyloid was also observed. Immunohistochemical stains revealed that a few plasmacytoid cells showed λ light chain staining, though most were κ： light chain positive. These cells also were positive for CD138 and CD56 but negative for CD20 and CD79. The findings were consistent with extramedullary plasmocytoma associated with a massive deposit of amyloid in duodenum. A subsequent workup for multiple myeloma was completely negative. The patient showed no signs of local recurrence or dissemination of the disease after 12 mo follow-up. Because of the association of plasmocytoma and amyloidosis, the patient must be followed up because of the possible systemic involvement of the neoplasm and amyloidosis in future.

Current surgical management of pancreatic endocrine tumor liver metastases

BACKGROUND: The management of metastatic disease in pancreatic endocrine tumors (PETs) demands a multidisciplinary approach and the cooperation of several medical specialties. The role of surgery is critical, even when a radical excision cannot always be achieved. DATA SOURCES: A PubMed search of relevant articles published up to February 2011 was performed to identify current information about PET liver metastases regarding diagnosis and management, with an emphasis on surgery. RESULTS: The early diagnosis of metastases and their accurate localization, most commonly in the liver, is very important. Surgical options include radical excision, and palliative excision to relieve symptoms in case of failure of medical treatment. The goal of the radical excision is to remove the primary tumor bulk and all liver metastases at the same time, but unfortunately it is not feasible in most cases. Palliative excisions include aggressive tumor debulking surgeries in well-differentiated carcinomas, trying to remove at least 90% of the tumor mass, combined with other additional destructive techniques such as hepatic artery embolization or chemoembolization to treat metastases or chemoembolization to relieve symptoms in cases of rapidly growing tumors. The combination of chemoembolization and systemic chemotherapy results in better response and survival rates. Other local destructive techniques include ethanol injection, cryotherapy and radiofrequency ablation. CONCLUSION: It seems that the current management of PETs can achieve important improvements, even in advanced cases.

EXPRESSION OF THE O^6－METHYLGUANINE－DNA METHYLTRANSFERASE GENE IN EIGHT HUMAN TUMOR CELL LINES

O6-methylguanine-DNA methyltransferase (MGMT) gene expression in 6 Mer+ (HeLa S3, SMMC-7721,SGC-7901, B-239, AGZY83-a, and Cc80 1) and 2 Mer- (SHG-44 , and HeLa MR) human tumor cell lines was examined. Southern blot analysis revealed no deletion, amplification, or rearrangement of the MGMT gene in these cell lines. However ,～ 1. 0 kb transcripts were detected in the 6 Mer+ cell lines but not in the 2 Mer-cell lines by Northern blot analysis. Furthermore,a rough correlation between MGMT activity and mRNA level in these cell lines was observed. These results suggest that transcriptional regulation of the MGMT gene is the molecular basis of the absence of MGMT activity in Mer-cell lines.

Ultrasound-guided fine needle aspiration biopsy in differential diagnosis of portal vein tumor thrombosis

BACKGROUND: Portal vein tumor thrombosis(PVTT) is a serious complication and a major metastatic way of hepa- tocellular carcinoma (HCC). But portal vein benign throm- bosis(PVBT) always appears in patients with hepatocirrho- sis, and PVTT should be differentiated from PVBT. The aim of this study was to probe the value of ultrasound- guided fine needle aspiration biopsy in differential diagnosis of PVTT. METHODS: Twenty-two HCC patients with portal vein thrombosis and 8 hepatocirrhosis patients with portal vein thrombosis were studied by ultrasound-guided fine needle aspiration biopsy. Twelve portal vein thrombosis filling portal vein embranchment of the 30 portal vein thrombosis patients were examined by 18G automatic biopsy. The positive rates of aspiration biopsy cytology and histology were calculated and compared with those of automatic biopsy. RESULTS: The positive rates of fine needle aspiration biop- sy cytology and histology were 93.3% (28/30) and 90.0% (27/30), respectively. They were not different markedly from that of automatic biopsy 91.7% (11/12). In aspira- tion biopsy of 22 HCC patients with PVTT, HCC cellular was found in 19 portal vein thrombosis patients (86.4%) by cytology examination and in 18 portal vein thrombosis patients (81.8%) by histology examination. In total, 20 tumor thrombi were detected. The other two were diag- nosed as benign thrombosis. No HCC cell and/or tissue was observed in 8 patients with hepatocirrhosis associated with portal vein thrombosis. CONCLUSIONS: Ultrasound-guided fine needle biopsy in detecting PVTT shows a high positive rate and is of diag- nostic value. The positive rate is not apparently different from that of automatic biopsy. Hence the case that fails to be diagnosed by color Doppler flow imaging ( CDFI) and pulsed Doppler can be detected early by ultrasound-guided fine needle aspiration biopsy.

Duodenal localization of plasmablastic myeloma

Gastrointestinal involvement in plasma cell neoplasms,either as primary localizations(extramedullary plasma-cytomas) or as secondary involvement in systemic multiple myeloma, is a well-known event. Accurate histological examination is crucial in defining the diag-nosis. In this report, an uncommon case of duodenal localization of myeloma with plasmablastic features is described, with emphasis on the role of clinical data and findings from ancillary immunostaining techniques to avoid misdiagnosis.

The expressions and significance of Hpa and bFGF in oral squamous-cell carcinoma

Objective： To investigate the expressions of heparanase （Hpa） and basic fibroblast growth factor （bFGF） in oral squamous-cell carcinoma （OSCC）, and to evaluate the relationship between the expressions and tumor angiogenesis and progression. Methods： The expressions of Hpa mRNA and bFGF mRNA of OSCC were examined using in situ hybridization. The microvascular density （MVD） was assessed through immunohistochemistry staining. Results： The expressions of Hpa mRNA and bFGF mRNA were associated with tumor MVD and lymph node metastasis. Concomitant expression of Hpa mRNA and bFGF mRNA was associated with higher tumor MVD as compared with expression of either factor alone. Conclusion： Hpa and bFGF might contribute to the angiogenesis and lymph node metastasis in OSCC and they cooperate in promoting vascularization.