Haemangiomas in kidneys with end-stage renal disease: a novel clinicopathological association

Primary intrarenal hemangioma - A series of 39 cases

Intrarenal hemangiomas lack concise clinicopathologic information, due to the predominance of single case reports and inclusion of other vascular neoplasms and hemangiomas of perirenal, hilar, and renal vein origin. Herein, in this multi-institutional study we evaluate clinicopathologic features of 39 intrarenal hemangiomas. The median age was 62 years (range = 27-94 years; 2:1 male to female ratio), with left-sided predominance (left = 21, right = 13; one case was bilateral). The median tumor size was 1.5 cm (0.2-10 cm). Two cases arose from transplanted kidneys. Most were asymptomatic (n = 30, 86 %), even though most surgical interventions (19 partial, 19 radical, 1 biopsy) were due to hemangiomas (n = 24, 62 %). Synchronous renal neoplasms were present in 9 (23 %) patients, including clear cell renal cell carcinoma (RCC) (n = 4), angiomyolipoma (n = 2), oncocytoma (n = 2), and chromophobe RCC (n = 1). Multifocal hemangiomas (n = 5) were seen in cases with end stage renal disease. Intrarenal hemangiomas were mostly anastomosing (n = 18; 46 %), followed by capillary (n = 15; 38 %), and cavernous (n = 6; 16 %) subtypes. Fibrin thrombus (n = 9; 23 %) and extramedullary hematopoiesis (n = 4; 10 %) were occasionally present, the latter being only in the anastomosing subtype. Immunohistochemistry was performed on a majority (n = 33, 84 %) of hemangiomas, with vascular markers CD31 and CD34 and lack of PAX8 were most used for diagnosis. 30 patients had follow-up (median 48 months, range 1-241 months), none showed disease progression/recurrence. This study provides comprehensive observation of the largest intrarenal hemangioma cohort, highlighting their frequent cause of surgical intervention when present, predominance of anastomosing subtype, multifocality in end stage kidney disease, and occasional concurrent ipsilateral neoplasms.

Intraoperative tumor capsule injury in patients with renal cell carcinoma receiving partial nephrectomy

OBJECTIVE

We investigated the impact of intraoperative tumor capsule injury (TCI) during robot-assisted partial nephrectomy (RAPN) or laparoscopic partial nephrectomy (LPN) on oncological outcomes, as well as underlying factors of intraoperative TCI for improving surgical outcomes.

METHODS

A total of 253 patients who underwent RAPN or LPN between 2010 and 2022 were retrospectively analyzed and were divided into two groups: non-TCI and TCI groups. The background was compared between two groups. We investigated the surgical records or video to evaluate TCI and seek the possible causes for TCI. Multivariate logistic regression analysis was performed to identify prognostic factors for cancer recurrence.

RESULTS

Of the 253 patients, 227 have renal cell carcinoma (RCC), with 29 patients having TCI. The TCI group had larger tumors, a lower rate of trifecta achievement, higher bleeding, higher T stage, and a lower rate of clear cell RCC (ccRCC) histological types as compared to non-TCI group. Disease recurrence rate was 13.8% with TCI and 1.0% with non-TCI (odds ratio 15.7; 95% confidence interval, 2.73-90.1; p = 0.003). Univariate and multivariate analyses confirmed TCI as an independent prognostic factor for disease-free survival. Compared with ccRCC, non-clear cell RCC (non-ccRCC) was found to have a higher probability of TCI and a significantly thinner capsule thickness on pathological evaluation.

CONCLUSION

TCI had a negative impact on oncological outcomes. Surgeons should consider thickness of tumor capsules, especially in cases with non-ccRCC, to minimize the risk of TCI during partial nephrectomy.

Common Diagnostic Challenges in Genitourinary Mesenchymal Tumors: A Practical Approach

Mesenchymal neoplasms within the genitourinary tract include a wide spectrum of tumors, ranging from benign to malignant, and tumors of uncertain malignant potential. Except for stromal tumors of the prostate, which originate from the specific prostatic stroma, these neoplasms generally resemble their counterparts in other body sites. The rarity of these neoplasms and the limitation associated with small biopsy samples present unique diagnostic challenges for pathologists. Accurate diagnosis is paramount, as it significantly influences prognosis and guides management and treatment strategies. This review addresses common diagnostic scenarios, discusses key differential diagnoses, and sheds light on potential diagnostic pitfalls.

Molecular mechanism of formation and destruction of a pseudo‑capsule in clear cell renal cell carcinoma

The process and molecular mechanisms underlying the formation and destruction of a pseudo-capsule (PC) in clear cell renal cell carcinoma (ccRCC) are poorly understood. In the present study, the PCs of surgical specimens from primary tumors and metastatic lesions in 169 patients with ccRCC, and carcinogen-induced ccRCC rat models were semi-quantified using the invasion of PC (i-Cap) score system. This was based on the relationship among the tumor, PC and adjacent normal tissue (NT) as follows: i-Cap 0, tumor has no PC and does not invade NT; i-Cap 1, tumor has a complete PC and does not invade into the PC; i-Cap 2, tumor with focal absences in the PC, which partially invades the PC but not completely through the PC; i-Cap 3, tumor crosses the PC and invades the NT; i-Cap 4, tumor directly invades the NT without a PC. The study suggested that PC formation was not observed without physical compression, and also revealed that tumor invasion into the PC was a prognostic factor for postoperative oncological outcomes. Higher i-Cap, Fuhrman grade and tumor size were independent poor prognostic factors for postoperative disease-free survival. mRNA expression arrays generated from carcinogen-induced ccRCC rat models were used to explore genes potentially associated with the formation and destruction of a PC. Subsequently, human ccRCC specimens were validated for four genes identified via expression array; the results revealed that collagen type 4A2, matrix metalloproteinase-7 and l-selectin were upregulated alongside the progression of i-Cap score. Conversely, endoglin was downregulated. In conclusion, the present study provides insights into the formation and destruction of a PC, and the results may aid the treatment and management of patients with ccRCC.

Unraveling Anastomosing Hemangioma: A Case Report

Anastomosing hemangioma is a rare and benign subtype of capillary hemangioma, a soft tissue tumor. It tends to be asymptomatic, causes abdominal pain and hematuria, and is more common in the genitourinary tract. It can be confused with paragangliomas or ectopic pheochromocytomas. Pathology shares characteristics with angiosarcoma, particularly in well-differentiated areas. Diagnosis without a surgical specimen is difficult and is based on clinical characteristics, laboratories, and imaging behavior similar to hemangiomas in other locations. When in doubt, a diagnosis can be supported by a percutaneous biopsy. The prognosis is good, without relapses or metastases. Early identification with follow-up can avoid surgical interventions.

Radiologic and pathologic correlation of a renal venous hemangioma

Renal hemangiomas, including the rare subtype of venous hemangioma, are typically non-cancerous, often asymptomatic, and usually discovered incidentally during imaging studies. Here, we report a unique case of a 59-year-old African-American female with a renal venous hemangioma that initially mimicked papillary-type renal cell carcinoma (RCC-pt) on imaging studies. The patient's presentation included a long history of rectal bleeding and an incidental discovery of a hypoattenuating mass in the left kidney during a contrast-enhanced CT scan. Renal MRI revealed a 3.5 cm left renal lower pole mass, presenting as heterogeneously hyperintense on T1-weighted images and hypointense on T2-weighted images, with gradual mild enhancement post-contrast. Subsequent total nephrectomy confirmed the histopathological diagnosis of a venous hemangioma. This case underlines the need for recognizing unique imaging features of renal venous hemangiomas, contributing to the differential diagnosis of T2 dark hypoenhancing renal masses. Correct interpretation may prevent unnecessary invasive procedures and operations, thereby improving patient management and outcomes.

Hepatic anastomosing hemangioma: A case report

BACKGROUND

Anastomosing hemangioma (AH) is a rare benign vascular tumor, which is often discovered in the genitourinary system and paravertebral region and rarely occurs in the liver. AH lacks specific clinical manifestations and is prone to overtreatment.

CASE SUMMARY

A 29-year-old male patient sought medical attention due to the discovery of a liver tumor for 2 years and tumor enlargement for 7 mo. The preoperative diagnosis suggested the possibility of focal nodular hyperplasia. However, due to the rapid increase in the volume of the liver tumor, the possibility of malignancy cannot be ruled out. After surgical treatment, the diagnosis was confirmed as liver AH, and there was no recurrence during long-term follow-up after surgery.

CONCLUSION

Hepatic AH, as a benign tumor of blood vessels, lacks specific clinical manifestations. It can manifest as a stable tumor in the liver with a rapid increase in the volume in a short period of time, similar to a malignancy. Therefore, for cases with short-term progressive enlargement of intrahepatic masses, clinicians should broaden the scope of diagnosis and treatment, reduce misdiagnosis rates, and avoid overtreatment.

Spermatic cord anastomosing hemangioma mimicking a malignant inguinal tumor: A case report and literature review

Background

Anastomosing hemangioma (AH) is a rare vascular tumor and occurs in various organs. It is difficult to distinguish AH from malignant tumors even through multimodal imaging examination. AH located in the inguinal region is even rare. We present the diagnosis and treatment of a patient with spermatic cord AH in detail and conduct a literature review.

Case Report

An 84-year-old Chinese man had swelling pain in his right scrotum. A hard and fixed mass was palpable in the right inguinal region. Preoperative radiological examination considered it a neurogenic or vascular tumor. Malignant soft tissue sarcoma could not be excluded. He underwent radical inguinal right orchiectomy under intraspinal anesthesia. The diagnosis of spermatic cord AH was confirmed by pathological examination. The patient recovered uneventfully and remained disease-free during an 18-month follow-up.

Conclusion

Spermatic cord AH is quite rare and could be misdiagnosed as a malignant tumor. Pathological evidence might be necessary. The optimal choice of treatment should be determined through a comprehensive assessment of both tumor and patient factors.

Primary vascular tumours of the kidney

Primary vascular tumours of the kidney are rare and may pose diagnostic difficulties because of their similar clinical, morphological, and immunohistochemical features. This article summarizes the clinical and pathological features of primary renal angiosarcoma and anastomosing haemangioma of the kidney including epidemiology, genetics, and prognosis. Renal anastomosing haemangiomas are benign neoplasms characterized by anastomosing capillary-sized vascular channels. These tumours are rare, with about 75 cases reported in the literature. Most anastomosing haemangiomas are found incidentally on ultrasound, computed tomography, or magnetic resonance imaging. Common symptoms include abdominal pain, haematuria, and abdominal mass. Renal anastomosing haemangiomas are characterized by recurrent mutations in GNAQ and GNA14 genes. The prognosis of anastomosing haemangioma is excellent. Primary renal angiosarcomas are malignant tumours showing endothelial differentiation. To date, 76 cases have been described in the literature. Primary renal angiosarcomas are frequently symptomatic. The clinical features of renal angiosarcomas are similar to those of renal anastomosing haemangiomas, including abdominal pain, haematuria, and abdominal mass. Angiogenesis-related genes and vascular-specific receptor tyrosine kinases such as KDR, TIE1, SNRK, TEK, and FLT1 are upregulated in angiosarcomas. Primary renal angiosarcomas are highly aggressive neoplasms with a poor prognosis despite surgical treatment, chemotherapy, radiotherapy, or targeted therapy.

An anastomosing hemangioma mimicking a renal cell carcinoma in a kidney transplant recipient: a case report

Background

Although anastomosing hemangiomas are very rare and benign vascular neoplasms, these tumors are more common among patients with end-stage kidney disease. Incidental finding of these tumors in the kidney or adrenal gland has been reported. Herein, we describe a case in which an anastomosing hemangioma was misdiagnosed as a renal cell carcinoma before kidney transplant.

Case presentation

A 35-year-old woman with lupus nephritis was admitted to our emergency department for suspected uremic symptoms of nausea and general weakness. She had received hemodialysis due to end-stage kidney disease, and a living-donor kidney transplantation from her father was planned. On pre-operative contrast-enhanced computed tomography and magnetic resonance imaging, a 1.7 cm renal cell carcinoma was observed in the right kidney. On staining after radical nephrectomy, irregularly shaped vascular spaces of various sizes were observed, with these spaces having an anastomosing pattern. As the findings of the anastomosing hemangioma are similar to those of a renal cell carcinoma on imaging, histology examination was necessary to confirm the diagnosis of anastomosing hemangioma and to prevent delay in listing for kidney transplantation. Good kidney function was achieved after transplantation, with no tumor recurrence.

Conclusion

Our case underlines the importance for prompt surgical resection of an enhancing renal mass to confirm diagnosis in patients scheduled for kidney transplantation to avoid any delay.

A case of giant anastomosing hemangioma of the kidney with extramedullary hematopoiesis: A great mimicker

Anastomosing hemangioma (AH) are rare mesenchymal neoplasms affecting kidney with about 50 cases reported in English literature. In general, they are accidentally detected during examination or imaging done for nonspecific symptoms or wellness check-up. There are no key diagnostic features on the imaging modalities. The most common preoperative diagnosis has been a malignant primary renal carcinoma. Surgical resection remains the mainstay of treatment and of choice in symptomatic lesions. We are presenting a rare case of giant AH of the kidney mimicking a renal cell carcinoma on imaging. The lesions are characterized by anastomosing sinusoidal-like vascular spaces lined by banal endothelial cells with occasional hobnail morphology and associated with extramedullary hematopoiesis. The treatment of choice could be a conservative approach in small and asymptomatic lesions and patients with pre-existing renal dysfunction; hence, this entity should be in the differential of vascular renal neoplasms considering its proclivity to the urogenital tract. This is the first case in Indian literature to the best of our knowledge.

Case Report on Anastomosing Haemangioma: An Unusual Vascular Tumor in Kidney

Anastomosing haemangioma is a rare benign vascular neoplasm, which may mimic angiosarcoma histologically. We here present a case of anastomosing haemangioma arising from the kidney. This patient presented with a large kidney mass and adrenal mass. The clinical and radiological findings were suspicious for renal cell carcinoma with metastasis. Radical nephrectomy and adrenalectomy were thus performed. Histopathological examination and immunohistochemical studies concluded a diagnosis of anastomosing haemangioma of the kidney and concurrent adrenal cortical adenoma. It is important to differentiate this tumor from other borderline or malignant vascular neoplasms.

Pediatric Anastomosing Hemangioma: Case Report and Review of Renal Vascular Tumors in Children

The case involves a 10-year-old child who underwent a left radical nephrectomy for what was believed to be a Wilms' tumor. Histopath examination indicated a benign vascular lesion, subsequently determined to be an anastomosing hemangioma of the kidney. A comparison with the previously cited pediatric patients with renal vascular tumors is provided, and the inconsistent diagnostic terminologies for these conditions are highlighted. The therapeutic implications of these predominantly benign renal tumors, in the context of the much more frequently encountered malignant neoplasms in children, are additionally discussed.

Multiple renal capillary hemangiomas in a patient with end-stage renal disease

Renal capillary hemangiomas are rare and benign vascular tumors which are typically incidentally discovered on imaging. Surgical excision is often performed, as imaging appearance is similar to malignant lesions. Renal hemangiomas are typically solitary and unilateral. We present a rare case of multiple renal capillary hemangiomas in a patient with end-stage renal disease. Two hemangiomas were detected on imaging and 2 smaller hemangiomas were detected upon pathological evaluation, suggesting there may be a wider prevalence of smaller, radiographically-occult renal hemangiomas.

Anastomosing Hemangioma: Short Review of a Benign Mimicker of Angiosarcoma

Anastomosing hemangioma is a rare neoplastic vascular lesion, histologically mimicking angiosarcoma. It is predominantly composed of irregularly anastomosing sinusoidal-like spaces lined by endothelial cells with minimal atypia, a frequently hobnail morphology, and minimally invasive margins. Since its original description in the genitourinary system, an increasing number of anastomosing hemangiomas have been reported, localized deep in the body in various organs, always with similar histologic features. It is more frequently asymptomatic, often discovered incidentally by imaging studies, owing to coexisting benign or malignant tumors. In renal cases, the most frequent clinical context is end-stage renal disease. There is overwhelming evidence of the benign nature of the lesion and an accurate diagnosis could prevent overtreatment. The differential diagnosis includes other benign vascular tumors, well-differentiated angiosarcoma, Kaposi sarcoma, and other vascular-rich neoplasms. We review the clinical and histopathologic characteristics of this peculiar lesion with an emphasis on the differential diagnosis.

Mesenchymal Neoplasms of the Genitourinary System: A Selected Review with Recent Advances in Clinical, Diagnostic, and Molecular Findings

Mesenchymal neoplasms of the genitourinary (GU) tract often pose considerable diagnostic challenges due to their wide morphologic spectrum, relative rarity, and unexpected incidence at GU sites. Soft tissue tumors arise throughout the GU tract, whether from adventitia surrounding or connective tissues within the kidneys, urinary bladder, and male and female genital organs. This selected article focuses on a subset of these lesions, ranging from benign to malignant and encompassing a range of patterns of mesenchymal differentiation, where recent scholarship has lent greater insight into their clinical, molecular, or diagnostic features.

Anastomosing haemangioma of liver: A case report

Anastomosing haemangioma (AH) is a recently described, unusual variant of capillary hemangioma that appears to be unique to the genitourinary system, with a particular proclivity for the kidney. AH is a subtype of capillary haemangioma, which is rarely encountered in clinical practice, particularly in the liver. We herein present the case of a 57-year-old woman with an incidental finding on magnetic resonance imaging of a local lesion in the liver, sized 3.3×3.0 cm. The patient underwent hepatectomy with a good postoperative recovery. The histopathological diagnosis was AH of the liver. To the best of our knowledge, this is the first case report of hepatic AH.

Renal capillary haemangioma associated with renal cell carcinoma and polycythaemia in acquired cystic disease

Capillary haemangiomas are relatively common tumours, typically occurring in the subcutaneous tissue during childhood. However, visceral occurrence is very rare. These tumours make up a subset of vascular lesions that have previously, although rarely, been described in case reports in association with the kidney. Here we review the literature and describe a capillary haemangioma occurring in the renal hilum found to be coexistent with end-stage renal disease, renal cell carcinoma and polycythaemia. To our knowledge, this is the first case report to describe the occurrence of this tumour in the renal hilum in association with this constitution of renal pathologies.

Recurrent GNAQ mutations in anastomosing hemangiomas

Anastomosing hemangiomas are recently described benign vascular lesions that occur chiefly in the genitourinary tract and paravertebral soft tissues. Owing to their rarity and unusual cytoarchitectural features, anastomosing hemangiomas are frequently confused with low-grade angiosarcomas. The specific genetic alterations underlying these lesions are currently unknown. We performed capture-based next-generation DNA sequencing analysis on 13 anastomosing hemangiomas and identified frequent somatic mutations in the heterotrimeric G-protein alpha-subunit, GNAQ. Nine of 13 cases (69%) harbored a somatic mutation at GNAQ codon 209, a known hotspot that is commonly mutated in uveal melanoma and blue nevi, as well as various congenital vascular proliferations. No other pathogenic or likely pathogenic mutations were identified in these genetically simple lesions. The finding of a recurrent driver mutation in the G-protein signal transduction pathway provides strong evidence that anastomosing hemangiomas are indeed clonal vascular neoplasms.

Comparison of Renal Anastomosing Hemangiomas in End-Stage and Non–End-Stage Kidneys: A Meta-Analysis With a Report of 2 Cases

Background. Renal anastomosing hemangioma (RAH) is a very rare distinct entity composed of anastomosing sinusoidal (spleen-like) capillary-sized vessels lined by flat or hobnail endothelial cells. Most of the published cases of RAH occurred in the setting of end-stage renal disease (ESRD). Methods. We present 2 cases of RAH in ESRD along with a literature review. We compared clinicopathologic features of RAHs in end-stage and non–end-stage kidneys. A meta-analysis was conducted with PubMed and a manual search through references of relevant publications. Individual patient data gathered from the literature were used in the analysis. Results. Our systematic review revealed 49 RAHs, including our 2 cases. Thirty-two (65.3%) cases were in ESRD, only 17 (34.7%) were in patients with non-ESRD. RAHs in ESRD were in younger patients, smaller in size, multifocal, and seen more with renal epithelial neoplasms when compared with RAHs in non-ESRD ( P < .05). Extramedullary hematopoiesis was seen mostly in RAHs in ESRD kidneys (85% vs 41.7%) ( P = .018). Follow-up data were available for 25 cases with a mean follow-up of 24.58 ± 38.54 months. Recurrence, metastasis, or death have never been described related to RAH in any patients. Conclusions. In conclusion, RAHs are rare and mostly arise in kidneys with end-stage damage. RAHs in ESRD and non-ESRD differ in terms of clinicopathologic features.

Anastomosing hemangioma: report of two renal cases and analysis of the literature

Background

Anastomosing hemangioma (AH) is a very rare vascular tumor mimicking angiosarcoma, predominately observed in kidney and less frequently in other organs. We present two new renal cases of AH at opposite ends of the clinical presentation spectrum, provide review of the literature and compare the epidemiological, clinical and pathological profiles of renal and non-renal cases.

Case presentation

The first occurred in a 64-year-old woman presented with back pain and the second, a multifocal lesion, in a 47-year-old man with end stage renal disease (ESRD). Histology disclosed a vascular tumor with striking anastomosing pattern, minimal nuclear atypia and locally infiltrative pattern, mimicking superficially angiosarcoma. Extramedullary hematopoiesis, extensive perirenal fat entrapment and increased number of mast cells were additional features in the second lesion. Both patients are well, without disease, 25 and 14 months after diagnosis.

Conclusion

Comprehensive review and analysis of the published literature show that the growing number of non-renal AHs exhibits similar epidemiologic, clinical, biologic and histologic characteristics with renal AHs and most mild differences vanish after exclusion of cases associated with ESRD. Better understanding of AH pathogenesis will contribute to optimal treatment choices.

Spontaneous rupture of the kidney in the patients with synchronous renal hemangioma and nephrogenic hypertension

Most renal neoplasms in adults are epithelial in origin and mesenchymal tumors are rarely encountered. Vascular tumors and tumor-like lesions account for a very small subset. Hemangioma of the kidney is a rarely seen benign vascular neoplasm that probably arises from angioblastic cells. Its general sign is macroscopic hematuria with or without pain. Preoperative diagnosis is difficult or impossible. Previously, spontaneous rupture of the kidney caused by renal hemangioma was not reported in the English literature. In this study, two cases with a history of nephrogenic hypertension who presented with spontaneous renal rupture are presented. There wasn't any trauma history in the background of our patients. A long-standing nephrogenic hypertension was present in both patients. Patients underwent radical nephrectomy due to rupture of the renal tumor. In histopathological examination, capillary hemangioma was detected in the renal medulla in both cases. Patients didn't need antihypertensive therapy during the postoperative period.

Updates in Benign Lesions of the Genitourinary Tract

The genitourinary tract is a common site for new cancer diagnosis, particularly for men. Therefore, cancer-containing specimens are very common in surgical pathology practice. However, many benign neoplasms and nonneoplastic, reactive, and inflammatory processes in the genitourinary tract may mimic or cause differential diagnostic challenges with malignancies. Emerging clinicopathologic, immunohistochemical, and molecular characteristics have shed light on the pathogenesis and differential diagnosis of these lesions. This review addresses differential diagnostic challenges related to benign genitourinary tract lesions in the kidney, urinary bladder, prostate, and testis, with emphasis on recent advances in knowledge and areas most common in diagnostic practice.

A giant cord hemangioma with extramedullary hematopoiesis and elevated maternal serum human chorionic gonadotropin: a case report and review of the literature

A case of prenatally diagnosed, giant cord hemangioma is reported, which was accompanied by the elevation of maternal serum alpha-fetoprotein (MS-AFP) and human chorionic gonadotropin (MS-hCG) levels. A 30-year-old woman without a previous history of gravida or para, presented with intermittent abdominal pain at 26 weeks of gestation. Doppler studies showed the fetus developing heart failure as the tumor grew larger. Caesarian section was performed at 29 weeks of gestation. Macroscopic examination of the placenta revealed a 17.0 × 10.0 × 7.0 cm tumor localized at the placental end of the umbilical cord. Microscopically, the tumor was composed of small arborizing vessels proliferating in the myxoid background, and the tumor cells were positive for AFP by immunohistochemistry. Extramedullary hematopoiesis was seen in the tumor vascular channels. The present case is one of the largest umbilical cord hemangiomas reported in the literature, and the first hemangioma case with MS-hCG elevation, extramedullary hematopoiesis, and positive AFP staining in the cord hemangioma. Its clinical course and detailed pathological findings are presented along with a review of the related literature.

Anastomosing hemangioma of the kidney: a literature review of a rare morphological variant of hemangioma

BACKGROUND

Anastomosing hemangioma (AH) of the kidney is a recently described morphological variant of hemangioma. It poses a diagnostic dilemma for clinicians because of its rarity and the overlapping features it shares with other renal vascular tumors. The aim of this paper is to review all the cases of AH of the kidney in the literature.

METHODS

The literature was extensively searched for case reports of AH of the kidney and the clinical and pathological characteristics of the tumor were extracted.

RESULTS

A total of 45 cases were reviewed. The mean age of presentation was 50 years (range, 15-83 years) and male sex accounted for 68.8% of the cases reviewed. AH of the kidney was mostly unilateral with only 4 cases of bilateral involvement of the kidney. The average size of the tumor is 1.5 cm (range, 0.1-7 cm). Incidental finding of AH of the kidney accounted for 62% of the cases reviewed. The ultrasound findings demonstrated varying echogenicity and the tumor appeared as solid and well demarcated heterogeneous masses on CT. The average follow up of the patients in this review was 26 months (range, 1-156 months).

CONCLUSIONS

AH of the kidney is a rare vascular tumor and a morphological variant of hemangioma. It has a characteristic sinusoidal architecture with a semblance of splenic sinusoids. It has overlapping clinical and imaging features with other vascular tumors of the kidney. Histological review and immunohistochemical studies are essential for accurate diagnosis. AH runs a benign course without evidence of disease recurrence during follow up.

Characterization of Fibromuscular Pseudocapsule in Renal Cell Carcinoma

Pseudocapsule in renal cell carcinoma (RCC) has been described but little is known about its prevalence and extent. Pseudocapsule was analyzed in 105 RCCs (44 clear cell, 44 chromophobe, 17 papillary). Pseudocapsule was graded as follows: grade 1, thickness comparable to adjacent muscular arteries; grade 2, thickness more than twice the diameter of adjacent muscular arteries; grade 3, grade 2 findings with vasculopathy. Tumor size, tumor regression, and International Society of Urologic Pathology (ISUP) nucleolar grade were recorded. Cases with grade 3 pseudocapsule were stained with elastic silver stain, Alcian blue, smooth muscle actin, and CD31. More clear cell RCCs had pseudocapsule (89%, 39/44) than chromophobe (30%, 13/44) and papillary (35%, 6/17). Average tumor size with pseudocapsule was 3.9 cm; average tumor size without pseudocapsule was 3.8 cm (P = .77). Grade 2 pseudocapsule was common in clear cell RCC (56%, 22/39). Chromophobe and papillary RCC had grade 1 pseudocapsule in 77% (10/13) and 83% (5/6) of cases. Grade 3 pseudocapsule was only seen in clear cell RCC (10%, 4/39). No correlation was noted between degenerative tumor changes, tumor size, ISUP nucleolar grade, and presence and grade of pseudocapsule. Smooth muscle actin and CD31 showed abundant smooth muscle component and rich vasculature within the pseudocapsule. Arterial elastic membrane disruption and/or fibrointimal mucin deposits were present in grade 3 pseudocapsule. Thus, pseudocapsule is rather characteristic and more prominent in clear cell, less frequent in chromophobe, and rare in papillary RCC. Its presence may be evaluated radiologically or in biopsy specimens with scant tumor fragments.