UNCLASSIFIED Anastomosing Hemangioma Incidentally Found in Kidney or Adrenal Gland: Study of 10 Cases and Review of Literature Jun Zhou1*, Xiaoqun Yang1*, Luting Zhou1,Ming Zhao2, Chaofu Wang1 Purpose: To describe and report a series of renal and adrenal anastomosing hemangioma (AH) and to investigate its distinctive clinicopathologic features and review its clinical data available in the literature. Materials and Methods: Clinical data of 10 AHs were retrospectively studied. Imaging and histologic features were re-evaluated and summarized. Immunostaining markers performed include CD31, CD34, ERG, Fil-1, D2-40, AE1/AE3, SMA, CD10, HHV8, S100, Ki-67. A follow-up of all cases was performed. Other AHs published in PubMed and Web of Science were reviewed. Results: All of 10 AHs were found incidentally in 5 female and 5 male patients (median age, 48.5 years; mean, 51.7 years) and involved unilateral kidney (n=7) and adrenal glands (n=3) respectively. All lesions were well-de- fined in imaging and histologic examination. AHs were morphologically characterized by prominent anastomosing vascular channels without evidence of infiltration to surrounding normal tissues and significant cellular atypia. CD31, CD34, ERG were positive and Ki-67 showed typically low positivity (< 3%). All Patients underwent a mass resection and none of them had evidence of recurrence. Together with other cases published, the AHs showed distinctive clinicopathologic features with an excellent prognosis. Conclusion: Renal or adrenal AH is a very rare vascular tumor. They have distinctive histologic features and a favorable prognosis. It is frequently mimicking well-differentiated angiosarcomas which easily results in unneces- sary overtreatment in clinical practice. Keywords: anastomosing hemangioma; clinicopathology; prognosis; kidney; adrenal gland INTRODUCTION Vascular tumors are large and heterogeneous en-tities with varying endothelial differentiation.(1) Their complex categorization and clinical-biologic be- haviors are usually not familiar to the clinicians.(2) So are the pathologists due to the broadly morphologic and relevant little genetically available information for the majority of vascular lesions and hence the differential diagnosis could be pretty challenging.(3) Primary benign vascular lesions arising in the kidney or adrenal gland are distinctly rare, among which arteriovenous malfor- mation, angiomatous endothelial cysts, hemangioma, and angiosarcoma are the most common types.(4,5) Anastomosing hemangioma (AH), a very rare vascular tumor and was firstly described by Montgomery and Epstein in 2009.(6) One issue of concern for AH is mim- icking malignancy histologically that may result in un- necessary overtreatment. Although AH was originally considered to be a distinct vascular tumor exclusively 1Department of Pathology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine Shanghai, China. 2Department of Pathology, Zhejiang Provincial People’s Hospital, Hangzhou, Zhejiang, China. * J. Z. and X. Y. contributed equally. *Correspondence: Department of Pathology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Ruijin Er Road, Huangpu District, Shanghai, 200025, China, Tel: +86 17321086332, E-mail: wangchaofu@126.com. *Department of Pathology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Ruijin Er Road, Huangpu District, Shanghai, 200025, China, Tel: +86 17701879546, E-mail: yangxiaoqun963@163.com. Received May 2020 & Accepted August 2020 occurring in the genitourinary tract, the following re- ports indicated they can develop in various anatomic locations such as soft tissue, liver, colon, bladder, skin, etc.(7-10) Although some renal and adrenal AHs were sporadically reported, most pathologists and clinicians are still unfamiliar with this entity. Herein, we added 10 AHs arising in the kidney or adrenal gland AH to further investigate their clinicopathologic features and emphasize its diagnostic pitfalls and mimickers. MATERIALS AND METHODS Subjects This study was approved by the Institutional Review Board at the Department of Pathology, Ruijin Hospi- tal, Shanghai Jiaotong University School of Medicine (Shanghai, China). A total of 10 patients specimens entered our study, including 2 consultant cases and 8 surgical specimens. All of them have complete clinical data. All hematoxylin and eosin (HE)-stained (DAKO Urology Journal/Vol 17 No. 6/ November-December 2020/ pp. 650-656. [DOI: 10.22037/uj.v0i0.5514] CoverStainer; Agilent, Santa Clara, CA, USA) slides were independently reviewed by 2 experienced pa- thologists (C.F.W. and J. Z.) under a light microscope (BX43; Olympus Corporation, Tokyo, Japan). Fol- low-up was performed in the office setting or by tele- phone interview. Immunohistochemistry (IHC) IHC evaluation of consultant cases was recorded ac- cording to the submitted immunostaining slides. Each surgical specimen was specially re-sectioned. 4-μm thick sections were taken from 10% formalin-fixed and paraffin-embedded tissue blocks followed by immuno- histochemical staining using commercially available antibodies as follows: CD31 (monoclonal, prediluted; Dako, Glostrup, Denmark ), CD34 (QBEND, predi- luted; Dako, Glostrup, Denmark), ERG (EP111, 1:200 dilution; ZSGB-BIO, Beijing, China), Fil-1(MRQ-1, 1:50 dilution; ZSGB-BIO, Beijing, China), D2-40 (D2- 40, prediluted, Dako, Carpinteria, CA, US), AE1/AE3 (AE1/AE3, prediluted; Dako, Carpinteria, California, USA), SMA(1A4, 1:200; ZSGB-BIO, Beijing, China), CD10(56C6, 1:100 dilution; Leica Biosystem, Newcas- tle, UK), HHV8(LN35, 1:100 dilution; Abcam, Hong- Kong, China), S100 (Polyclonal, prediluted; Dako, Glostrup, Denmark), and Ki-67 (MIB-1, prediluted; Dako, Glostrup, Denmark). Detection of antibody bind- ing was obtained using the universal immunoperoxi- dase polymer method (Envision-kit; Dako, Carpinteria, CA, USA). A Dako automated immunohistochemistry system (Dako, Carpinteria, CA, USA) was performed according to the manufacturer's protocol. The IHC re- sults were independently interpreted by 2 experienced pathologists (L. Z. and C.F.W.). Literature review and data analysis Literature in PubMed and Web of Science before April 2019 were reviewed. Only the cases that met the diag- nosis of AH and had complete clinicopathologic and follow-up data entered our analysis. Descriptive statis- tics of the common features of AHs (epidemiology, de- mography and clinical features) were performed using the MS-office 2016 Excel software (Microsoft, Red- mond, WA, USA). RESULTS Clinical features and follow-up As a regional consultation and treatment center, the pa- tients in our group mainly came from the eastern China during April 2015 to January 2019. The main clinical data of AHs are summarized in Table 1. A total of 8 renal and 2 adrenal lesions in 5 females and 5 males, ranging in age from 28 to 71 years (median, 48.5 years; mean, 51.7 years) were investigated. All the patients were asymptomatic and laboratory test results did not show significant abnormalities. Each lesion was acci- dentally found by routine physical examination, 1 of which was appreciated by imaging before her preop- erative preparation for hepatic carcinoma. All lesions Anastomosing Hemangioma-Xiaqun et al. Unclassified 651 Figure 1. Represented imaging features of AH. A contrast-enhanced CT scan showed a well-circumscribed solid tumor in the right kidney with peripheral enhancement at the arterial phage (A. axial; B. coronal), and homogeneous enhancement at portal phase (C). Coronal enhanced CT demonstrated a homogeneous enhanced lesion arising on the adrenal gland at arterial phage (D). demonstrated a blurred mass with a soft-tissue density in computed tomography (CT), 8 cases showed periph- eral enhancement at arterial phage and homogeneous enhancement at portal phase (Figure 1A-C); 2 cases directly displayed diffuse even enhancement at arteri- al phage (Figure 1D). All AHs were generally small, ranging in size from 0.8 to 3.9 cm (mean, 2.0 cm; me- dian, 2.0 cm). All follow-up data were available, show- ing no evidence of recurrence (average follow-up 33 months, range 10 to 46 months). Pathologic features Grossly, the tumors imparted gay-red or purple-red sol- id appearance. Microscopically, all AHs were well-cir- cumscribed and unencapsulated (Figure 2A). They typ- ically consisted of anastomosing capillary-like vascular channels with no or mild atypia of tumor cells (Figure 2B). Mitosis was consistently absent. Alternating cel- lular (Figure 2C) and acellular regions were readily apparent in 4 cases (cases 1, 2, 8 and 9). The acellular areas were characterized by loosely edematous or hy- aline stroma (Figure 2D). Proliferated vessels formed the glomerulus-like structure in 2 cases (cases 1, and 6). Case 10 had focally and centrally fibrosis. Extramedul- lary hematopoiesis (case 2), extracellular eosinophilic granular materials (case 1, Figure 2E), or foamy cells (case 4, Figure 2F) were also seen. Immunohistochemically, tumor cells of all the cas- es were consistently positive for vascular endotheli- al markers including CD31, CD34 (Figure 3A), ERG (Figure 3B), and Fli-1. None of the cases were immu- noreactive for AE1/AE3, EMA, PAX8, CD10, SMA, HHV8, S100, and D2-40. The proliferative index la- beled by Ki-67 was typically low (range, 1%-4; mean, 2.2%; Figure 3C). Clinical features summarized from publication Almost all AHs in the available literature were included to summarize the clinicopathologic features. (4,6-34) As depicted in Figure 4A, the 131 cases AHs (includ- ing our 9 cases) mostly reported from North America Figure 3. Immunophenotype of AH. The tumor cells expressed CD34 (A; magnification, 200×) and ERG (B; magnification, 200×), with a low proliferated index Ki-67 (C; staining H&E; magnification, 100×). Figure 2. Histologic features of AH. Low power showed a well-delineated lesion developing in the renal parenchyma (A, staining H&E; staining H&E; magnification, 40×). At medium power, AH was characterized by prominent anastomosing vascular lining by singly bland endothelial cells (B, staining H&E; magnification, 200×). Cellular regions were a florid proliferation of interconnecting capillary-like ves- sels (C, staining H&E; magnification, 100×). This adrenal AH showing distinct loosely edematous stroma may obscure the anastomosing growth pattern (D, staining H&E; magnification, 40×), however, the typical growth areas can be focally appreciated (inset). eosinophilic granular materials (E, staining H&E; magnification, 200×), or foamy cells (F, staining H&E; magnification, 200×) was occasionally seen. Anastomosing Hemangioma-Xiaqun et al. Vol 17 No 06 November-December 2020 652 Unclassified 653 (68%), Asia (17%), and Europe (11%). The patient's age ranged from 2 to 85 years (mean, 55.9; median, 56 yr.) with female average age slightly older than male. Of available cases, 80% is found incidentally without related symptoms (Figure 4C), and the remaining adopts pain, palpable mass, paresthesia, pleural effusion, neu- rologic deficits, hematuria, and other concurrent tumors (hepatic, renal, ovarian, endometrial carcinoma, etc.). Among all renal AHs, 24.4% associated with end-stage renal disease (ESRD). (4,18,25,30,31,34,35) Various involved anatomic locations were has been appreciated with the majority developing in kidney (n=51, 38.3%), spinal/ paraspinal region (n=20, 15%), adrenal gland (n=18, 13.5%), and liver (n=9, 6.8%) (Figure 4D). AH is usually solitary, but multiple lesions are also appreciable (Figure 4E); locations of the latter include kidney (45%), liver (20%), adrenal gland (10%), intes- tine (10%), paraspinal region (5%), ovary (5%), and breast (5%). The tumor can be solid, cystic, and sol- id-cystic in either imaging or gross examination (Fig- ure 4F), ranging in size from 0.5 to 12 cm (mean, 3.0 cm; median, 2.6 cm; Figure 4G). Identical to the most reported cases, all tumors in our series were asympto- matic and found incidentally. As depicted in Figure 4H, the reported ways of resection are listed as follows by decreasing percentage: simple lesion resection (47%), organ resection (26%), partial organ resection (18%), radical resection (9%). Almost all the patients were alive without evidence of disease during the follow-up (range: 1 to 156 months; median, 14 months; mean, Figure 4. Clinical data of AH from literature. The cases reported from a distinct region around the world, most of which derived from North America (A). The female average age is slightly older than male (B). Most of the tumors were incidentally found (C). Various in- volved locations were reported as yet, of which the most location was kidney (D). The majority demonstrated solitary lesion, but a subset of multiple lesion can also be appreciable (E). The texture of AH can be solid, cystic and solid-cystic (F). The tumors ranged in size from 0.5 to 12 cm, most of which clustering in 0.5 to 3.5 cm (G). The surgical method includes simple lesion resection, organ resection, partial organ resection, radical resection (F). Anastomosing Hemangioma-Xiaqun et al. 26.2 months), except that one patient was dead after 107 months since AH arising in the explant was found. DISCUSSION Hemangioma is a common soft tissue lesion and fre- quently arise in skin and subcutis.(7) The renal or adrenal hemangiomas are relatively rare, some of which have underlying other vascular diseases, such as Sturge-We- ber syndrome, Klippel-Trenaunay syndrome, von Hip- pel-Lindau syndrome or systemic angiomatosis. (36-39) AH is an extremely rare benign tumor. Although cases of AHs have been continuously reported since 2009, most arein the form of case reports, many clinicians were still unfamiliar with this entity. Originally, it is uncertain whether AHs represent a bona fide endotheli- al tumor or reactive or malformation.(7) However, from the views of the pathologist, the distinct morphologies resemble hemangioma, suggesting their tumor nature(7). Recently, recurrent GNAQ and GNA14 mutations were discovered in AH, supporting a role for this pathway in the pathogenesis of AHs and further indicating its true tumor nature.(11,28) Clinically, unlike the other vascular lesions, AHs tend to be asymptomatic without typical manifestation such as hematuria or flank pain(40). Therefore, it’s difficult to early find this lesion unless in few patients associated with some symptoms or ESRD who need additional re- nal examination. Radiologically, non-contrast CT may show hypodense solid or cystic lesions and contrast-en- hanced CT usually exhibits homogeneous enhance- ment or heterogeneous enhancement in the periphery. (9,16,24,33) However, imaging also seems not to help in differentiating AHs from other mimickers(15), although the angiosarcomas or renal cell carcinomas common- ly demonstrate central necrosis that large AHs still can have.(32) The rarely possible pre-operative diagnosis by radiologic studies may give rise to clinically conserv- ative management.(16) Laboratory biologic markers do not also help to recognize this disease. Nonetheless, the risk of AHs in patients who suffer from the chronic re- nal disease should be noted, due to its association with ESRD, particularly when there are relevant symptoms. Histologically, AH is typically well-demarcated with- out evidence of peripherally infiltration and neoplastic necrosis, the features practically pathognomonic when making a diagnosis.(4) It is characterized by intercon- nected sinusoidal capillary-like vessels lined by hob- nail or flat endothelial cells with no obvious atypia, multilayering, and mitosis, although focal regions may demonstrate dilated cavernous-like vasculature.(9,30,33) Some cases have prominent sclerotic areas and hence form an alternating acellular and hypocellular pattern. (33) Mast cells with dark granules sometimes could be appreciable, which is likely to be considered as atypical endothelium resulting in a misdiagnosis of malignan- cies.(7,34) In the peripheral regions of AHs, one usually finds the thrombotic fibrin-filled vessels, another fea- ture of this entity.(7) Tumor cells prototypically stain positive with endothelial markers such as CD31, CD34, ERG, factor VIII-related protein. The flagship diagnostic differentiation from AH is well-differentiated angiosarcoma due to its deficiency in limited atypia at times. The prominent anastomosing growth pattern is traditionally considered as a practical- ly pathognomonic feature of angiosarcoma. The Mor- phologic overlap between these two may facilitate diag- nostic pitfalls, particularly for the junior pathologist or in the small biopsy. In a contrast to well-differentiated angiosarcoma, AH does not show prominent nuclear atypia, increased proliferative activity, and mitosis, as well as multilayering of tumor cells.(7,13) Necrosis, oth- er than some cases with regressive changes, is usual- ly not present in AH.(13) However, a subset of highly differentiated sarcomas only shows very little atypia thoroughly, which may obscure their true malignant na- ture and give rise to erroneous diagnosis when telling AHs apart from angiosarcomas. The most crucial and consistent features are that contrary to AHs, angiosar- comas always have an infiltrative border with extensive destruction of renal parenchymal, peripheral collagen or adipose tissue.(4) Papillary endothelial hyperplasia (Masson’s tumor) can also form loosely anastomotic vascular structures mimicking AH or angiosarcoma, but the intravascular growth and reactive vessel wall can provide useful diagnostic clues(41). Concerning the treatment to AHs, the mainstay in the surgical resection. As discussed above, the primary sur- gical way of AHs is lesion resection only due to the dif- ficulty to recognize their true nature of aggressiveness. No matter what surgical procedures were taken, almost all patients lead a calm period in the follow-up. Any- way, the long-term follow-up data further support the bona fide benign biologic behavior of AH that warrants the surgeon's consideration to avoid unnecessary over- treatments, such as radical resection, extended lymph node dissection, and unnecessary pre-/post-operative chemotherapy or radiotherapy(42,43). However, there has been no consensus on the treatment for AHs. If the biop- sy diagnosis can be established, the concrete treatments such as embolization, lesion resection, partial or total nephrectomy may depend on the lesion size, location, and presence of symptoms(32). In our series, the surgical ways included lesion resection, organ resection, partial organ resection, none of the patients have evidence of recurrence, metastasis, and death, further indicating the innocent nature of AH. CONCLUSIONS Renal or adrenal AH is a very rare vascular tumor. They have distinctive histologic features and favorable prog- nosis but mimic well-differentiated angiosarcoma. 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