Recurrent GNAQ mutations in anastomosing hemangiomas

Incidental Hemangioma in Tubectomy and Hemorrhoidectomy Specimens: A Report of Two Cases

Benign vascular neoplasms, or hemangiomas, can develop anywhere in the body.As they are usually asymptomatic, they are discovered incidentally while evaluating other coexisting diseases or conditions. We herein report two cases of capillary hemangioma at two extremely rare sites. A woman in her early 30s with a history of nine months of amenorrhea came for safe confinement and underwent an elective lower segment cesarean section (LSCS) with bilateral concurrent tubectomy. Another case involved a man in his 40s who presented with bleeding per rectum for three months. Per rectal examination, two purplish red masses were noted at the 3 and 11 o'clock positions, which were noncompressible and did not bleed on touch. Subsequently, a hemorrhoidectomy was performed. A well-defined vascular lesion in the fallopian tube and hemorrhoidal tissue were seen during the histopathological examination, which was compatible with a capillary hemangioma. The vascular endothelium was emphasized by immunostaining with CD34.Due to the potential for these lesions to manifest as surgical emergencies, it is imperative for surgeons to recognize and appropriately manage such presentations.

Anastomosing haemangioma of adrenal gland: an unusual vascular tumour

With only 15 reported cases, anastomosing haemangioma of adrenal is a rare entity and usually presents as adrenal incidentaloma. A hypertensive, diabetic, non-smoker man in his late 60s presented with irritative voiding symptoms. On evaluation, he was found to have a urinary bladder mass and left adrenal incidentaloma measuring 8 cm. Metabolic evaluation confirmed it to be non-functional.The patient underwent transurethral resection of bladder tumour with left laparoscopic adrenalectomy. Intraoperatively, the adrenal tumour was highly vascular with multiple feeder vessels. Grossly it was soft, encapsulated with focal grey-brown areas. Microscopically, most of adrenal gland was replaced by anastomosing proliferating capillary vessels within framework of non-endothelial supporting cells reminiscent of splenic sinusoids. The tumour was positive for CD-31, CD-34, Glut-1 and SMA.Anastomosing haemangioma is a benign entity but it must be differentiated from angiosarcoma. Characteristic imaging features are not yet defined and is, therefore, difficult to diagnose preoperatively.

Capillary malformations

Capillary malformation (CM), or port wine birthmark, is a cutaneous congenital vascular anomaly that occurs in 0.1%-2% of newborns. Patients with a CM localized on the forehead have an increased risk of developing a neurocutaneous disorder called encephalotrigeminal angiomatosis or Sturge-Weber syndrome (SWS), with complications including seizure, developmental delay, glaucoma, and vision loss. In 2013, a groundbreaking study revealed causative activating somatic mutations in the gene (GNAQ) encoding guanine nucleotide-binding protein Q subunit α (Gαq) in CM and SWS patient tissues. In this Review, we discuss the disease phenotype, the causative GNAQ mutations, and their cellular origin. We also present the endothelial Gαq-related signaling pathways, the current animal models to study CM and its complications, and future options for therapeutic treatment. Further work remains to fully elucidate the cellular and molecular mechanisms underlying the formation and maintenance of the abnormal vessels.

Anastomosing haemangioma of the mediastinum: Clinicopathological series with radiological and genetic characterisation

AIMS

Anastomosing haemangiomas are benign tumours with anastomosing vascular channels that may mimic angiosarcoma. While anastomosing haemangiomas have been described in diverse locations, particularly the abdominal/paraspinal region, data on anastomosing haemangiomas in the mediastinum remain limited. We report the clinicopathological, radiological and molecular characteristics of the largest single-institutional series of mediastinal anastomosing haemangiomas.

METHODS AND RESULTS

In our pathology archives in 2011-23, we reviewed all vascular lesions involving the mediastinum and identified seven anastomosing haemangiomas. Clinical information was abstracted from medical charts; available radiological imaging was reviewed. Targeted DNA-based next-generation sequencing (447 genes, including GNAQ and GNA11) was performed on five cases. The seven patients included five women and two men, with an age range of 55-77 (median = 72) years. Of the six tumours with available radiology, two each were in the prevascular, visceral and paravertebral mediastinum, with lobulated peripheral enhancement in all tumours examined with contrast enhancement. Six patients underwent tumour resection; one patient received proton radiotherapy. Microscopically, each tumour was solitary and characterised by anastomosing capillary-sized vessels lined by hobnail endothelial cells. Fibrin microthrombi, hyaline globules and extramedullary haematopoiesis were common. In the five tumours analysed by next-generation sequencing, GNAQ p.Q209P was identified in one tumour; no additional reportable alterations were identified in the remaining cases. No recurrence was noted in the four patients with available follow-up of 3-58 (median = 9.5) months after resection.

CONCLUSION

While mediastinal anastomosing haemangiomas can microscopically mimic angiosarcoma, awareness of this entity and radiological correlation may help to circumvent this diagnostic pitfall.

Papillary Hemangioma Harbors Somatic GNA11 and GNAQ Mutations

Papillary hemangioma (PH) is a small, primarily dermal lesion occurring predominantly in the head and neck in both children and adults. Its signature characteristics are dilated thin-walled channels containing papillary clusters of mainly capillary-sized vessels and endothelial cytoplasmic eosinophilic inclusions. Given certain histopathologic similarities to congenital hemangioma which harbor mutations in GNAQ and GNA11 , we investigated whether similar mutations are present in PH. Seven PH specimens were studied. All presented in the first 4 years of life, with one being noted at birth. With the exception of one lesion, all were in the head and neck. Lesions were bluish and ranged in size from 0.5 to 2.8 cm. Four samples had GNA11 p.Q209L and 3 had GNAQ p.Q209L missense mutations. Mutations in GNA11 and GNAQ are associated with other types of somatic vascular lesions including capillary malformation, congenital hemangioma, anastomosing hemangioma, thrombotic anastomosing hemangioma, and hepatic small cell neoplasm. Shared mutations in GNA11 and GNAQ may account for some overlapping clinical and pathologic features in these entities, perhaps explicable by the timing of the mutation or influence of the germline phenotype.

Benign Vascular Lesions of the Breast: A Clinical, Radiographic, and Pathologic Review

Vascular lesions of the breast are uncommon, however, these are increasingly encountered now due to more frequent use of magnetic resonance imaging. They comprise a spectrum of lesions including benign, atypical, and malignant tumors. The prototype is a hemangioma, which is most often nonpalpable and is detected on routine screening. Different histopathologic subtypes of hemangioma have been described, including perilobular, venous, cavernous, and capillary hemangioma. Other benign vascular lesions include anastomosing hemangioma, a well-circumscribed proliferation of anastomosing blood vessels with lobular or diffuse growth pattern which affects a large segment of the breast, presenting as a painless slow enlarging palpable mass. Recent data suggest that benign vascular lesions diagnosed on core needle biopsy with concordant radiologic and pathologic findings do not require excision and have an excellent prognosis, except angiomatosis, which can be locally aggressive and may recur. The main focus of this study is to present the radiographic, gross, and histopathologic characteristics of benign vascular lesions of the breast and their differential diagnoses.

Anastomosing haemangioma of the adrenal gland: A clinicopathological series of seven cases

AIMS

Anastomosing haemangioma is a rare benign vascular neoplasm that may histologically mimic angiosarcoma. We report the largest single institution series of anastomosing haemangioma in the adrenal gland with emphasis on clinical and radiological features.

METHODS AND RESULTS

Our laboratory information system was searched for a 25-year period (1999-2023), yielding seven cases confirmed as anastomosing haemangioma of the adrenal gland after pathological re-review. Clinical, radiological and pathological information was obtained from medical charts and submitting pathologists. Of a total of seven patients, four (57.1%) were men and three women, ranging in age from 37 to 75 years (mean = 61). Six of seven patients underwent adrenalectomies and one had radical nephrectomy. Tumours ranged from 0.7 to 6.4 cm (mean = 2.1 cm) and five of seven (71%) were grossly well-circumscribed. Five of seven lesions were found incidentally at imaging for other indications. All tumours were unifocal except one, which presented with multifocal disease with a concurrent adjacent retroperitoneal anastomosing haemangioma. Three of five tumours imaged with contrast enhancement were almost completely hyperenhancing with a small central non-enhancing portion, features overlapping with pheochromocytoma. One of seven tumours involved the peri-adrenal adipose tissue with a focally infiltrative pattern. There were no recurrences or metastases in six patients with available follow-up data (median = 95 months).

CONCLUSIONS

Benign anastomosing haemangiomas of the adrenal gland tend to occur in older patients, may mimic pheochromocytoma on imaging and must be distinguished from angiosarcoma pathologically. Better awareness of this entity by pathologists, radiologists and surgeons is crucial to appropriate work-up, diagnosis and management.

Multimodal imaging features of retroperitoneal anastomosing hemangioma: a case report and literature review

Background

Anastomotic hemangioma is a rare subtype of capillary hemangioma primarily found in the genitourinary tract. We present a case of a patient with an anastomotic hemangioma located in the retroperitoneal space; then, we explore and summarize the imaging features from previously reported cases for accurate diagnosis.

Case presentation

A 57-year-old woman complained of left lower back pain. Contrast-enhanced ultrasound revealed a hypoechoic mass with "slow-in and slow-out" enhancement. Abdominal CT scan displayed a well-defined, round soft tissue mass in the right retroperitoneal region with obvious enhancement. MRI indicated low signal on T1-weighted imaging, high signal on T2-weighted imaging and diffusion-weighted imaging, and progressive enhancement after enhancement. Surgical removal of the tumor was performed. Histopathological examination exhibited a distinct tumor border with interconnected blood vessels and a cavity lined by a single layer of cubic endothelial cells. Immunohistochemistry confirmed the presence of CD31[+] and CD34[+]. The final pathological diagnosis was anastomotic hemangioma. No recurrence was observed during a 40-month follow-up.

Conclusion

Retroperitoneal anastomotic hemangioma is a rare and benign neoplasm that may be misdiagnosed as ectopic pheochromocytoma or angiosarcoma. This case report presents and analyzes the imaging characteristics of a series of retroperitoneal anastomotic hemangiomas, which can be valuable for future diagnoses and help prevent unnecessary surgeries.

Renal anastomosing haemangioma

Anastomosing haemangioma is a rare subtype of haemangioma, a benign vascular tumour. Its rarity stems from its low incidence and difficulty in obtaining an accurate diagnosis. In addition, its histological resemblance to malignant neoplasms may lead to unnecessary overtreatment. Here, we report the case of an asymptomatic male patient with a slight increase in kidney function who underwent an abdominal ultrasound and a CT scan for suspected renal cell carcinoma. Subsequently, the patient underwent laparoscopic left radical nephrectomy. Histological analysis revealed an anastomosing haemangioma. The patient is currently asymptomatic with no relapse or imaging progression. We also present a literature review on anastomosing haemangioma.

Mesenchymal Neoplasms of the Liver

Mesenchymal neoplasms of the liver can be diagnostically challenging, particularly on core needle biopsies. Here, I discuss recent updates in neoplasms that are specific to the liver (mesenchymal hamartoma, undifferentiated embryonal sarcoma, calcifying nested stromal-epithelial tumor), vascular tumors of the liver (anastomosing hemangioma, hepatic small vessel neoplasm, epithelioid hemangioendothelioma, angiosarcoma), and other tumor types that can occur primarily in the liver (PEComa/angiomyolipoma, inflammatory pseudotumor-like follicular dendritic cell sarcoma, EBV-associated smooth muscle tumor, inflammatory myofibroblastic tumor, malignant rhabdoid tumor). Lastly, I discuss metastatic sarcomas to the liver, as well as pitfalls presented by metastatic melanoma and sarcomatoid carcinoma.

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.

A case report of anastomosing hemangioma of the ovary

RATIONALE

Anastomosing hemangioma (AH) is a rare benign neoplastic vascular lesion that histologically resembles a well-differentiated angiosarcoma. AH commonly involves the urinary system and testes. However, these tumors can also involve the ovaries in some rare cases. This manuscript presents the case of a 28-year-old Chinese woman diagnosed with ovarian AH.

PATIENT CONCERNS

The woman was admitted to the hospital with a 4-month history of a right ovarian mass discovered by ultrasound (US) after a spontaneous abortion. The US examination showed a 4 cm × 4 cm irregularly shaped mass with a rich blood supply.

DIAGNOSES

AH of the right ovar.

INTERVENTION

The patient underwent laparoscopic surgery to remove the mass. The postoperative pathological examination revealed that the mass contained capillaries arranged in a characteristic anastomotic or confluent pattern commonly seen in AHs.

OUTCOMES

The mass was successfully removed. The follow-up examination at 7 months post-surgery showed that the patient recovered well, and no recurrence or metastasis was found.

LESSONS

AH of the ovary is a rare benign vascular tumor. On imaging examinations, AHs appear as mostly well-defined, heterogeneous nodules with peripheral enhancement as other benign nodules. However, a definitive diagnosis can only be achieved through histopathological examination.

Benign and low-grade superficial endothelial cell neoplasms in the molecular era

Vascular tumors are the most common mesenchymal neoplasms of the skin and subcutis, and they encompass a heterogeneous group with diverse clinical, histological, and molecular features, as well as biological behavior. Over the past two decades, molecular studies have enabled the identification of pathogenic recurrent genetic alterations that can be used as additional data points to support the correct classification of these lesions. The purpose of this review is to summarize the available data related to superficially located benign and low-grade vascular neoplasms and to highlight recent molecular advances with the role of surrogate immunohistochemistry to target pathogenic proteins as diagnostic biomarkers.

Anastomosing hemangioma of the liver: An unusual variant in abdominal MRI imaging

The liver is a rare site for anastomosing hemangiomas with only a few cases reported that characterize the lesions on magnetic resonance imaging (MRI). These lesions may be underreported due to overlapping features with classic hemangiomas. Anastomosing hemangiomas have a well-defined histological profile and are often diagnosed by biopsy in the setting of atypical imaging features.  We report a case of biopsy-proven hepatic anastomosing hemangioma found on a screening MRI for hepatocellular carcinoma in a 52-year-old female with cirrhosis. This lesion initially demonstrated interval growth but has shown no local recurrence in the 2-year surveillance period following microwave ablation.

Anastomosing Haemangioma: Report of Three Cases With Molecular and Immunohistochemical Studies and Comparison With Well-Differentiated Angiosarcoma

Anastomosing haemangioma (AH) is a newly described distinct vascular neoplasm that histologically may confuse with well-differentiated angiosarcoma (AS) for those who are unfamiliar with this rare entity. We aimed to identify molecular genetic differences between AHs and ASs by carrying out immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and next-generation sequencing (NGS). Immunohistochemically, all six cases showed positivity for cyclinD1 and pERK. All cases of AH showed focal weak positive reaction for p53 and MIB-1, and the IHCs for HIF-1α were all negative for all three cases. Those three cases of angiosarcoma revealed strong, diffuse positivity for p53, 50%–70% MIB-1 labelling, and multifocal, moderate to strong HIF-1α expression. To further clarify the difference in p53 expression, we carried out a FISH which revealed 17p polysomy in all three ASs whereas copy number aberration was absent in the AH group. In one AH case, the GNA11 c.627G > T nucleotide variant was detected. Due to the rarity and overlapping morphological features, AH might be difficult to separate from other vascular tumours, in particular from well-differentiated AS also featured by mild hyperchromatic, hobnail-like endothelial cells. The potential molecular differences between these two entities presented here may be used in support of the correct diagnosis.

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.

New molecular entities of soft tissue and bone tumors

PURPOSE OF REVIEW

The advances of molecular techniques have led to the refinement of the classification of mesenchymal tumors, leading to newly introduced entities in the recently published fifth edition of the WHO Classification of Soft Tissue and Bone Tumors, which are discussed in this review.

RECENT FINDINGS

For the first time, entities are included of which the name refers to the underlying molecular alteration including round cell sarcoma with EWSR1 -non-ETS fusions, CIC -rearranged sarcoma, and sarcoma with BCOR genetic alteration. EWSR1-SMAD3 -positive fibroblastic tumor and NTRK -rearranged spindle cell neoplasm are provisionally included as 'emerging' entities based on the underlying molecular alteration, though the entity still needs to be better defined. Other newly recognized entities are not named after their molecular change, but the molecular alteration helped to delineate them from others: atypical spindle cell/pleomorphic lipomatous tumor, anastomosing hemangioma, angiofibroma of soft tissue, myxoid pleomorphic liposarcoma, and poorly differentiated chordoma.

SUMMARY

Classification of mesenchymal tumors is increasingly based on the underlying molecular changes, although this cannot be interpreted separately from clinical, morphological, and immunohistochemical characteristics.

A novel somatic mutation in GNAQ in a capillary malformation provides insight into molecular pathogenesis

Sturge-Weber syndrome (SWS) is a sporadic, congenital, neuro-cutaneous disorder characterized by a mosaic, capillary malformation. SWS and non-syndromic capillary malformations are both caused by a somatic activating mutation in GNAQ encoding the G protein subunit alpha-q protein. The missense mutation R183Q is the sole GNAQ mutation identified thus far in 90% of SWS-associated or isolated capillary malformations. In this study, we sequenced skin biopsies of capillary malformations from 9 patients. We identified the R183Q mutation in nearly all samples, but one sample exhibited a Q209R mutation. This new mutation occurs at the same residue as the constitutively-activating Q209L mutation, commonly seen in tumors. However, Q209R is a rare variant in this gene. To compare the effect of the Q209R mutation on downstream signaling, we performed reporter assays with a GNAQ-responsive reporter co-transfected with either GNAQ WT, R183Q, Q209L, Q209R, or C9X (representing a null allele). Q209L showed the highest reporter activation, with R183Q and Q209R showing significantly lower activation. To determine whether these mutations had similar or different downstream consequences we performed RNA-seq analysis in microvascular endothelial cells (HMEC-1) electroporated with the same GNAQ variants. The R183 and Q209 missense variants caused extensive dysregulation of a broad range of transcripts compared to the WT or null allele, confirming that these are all activating mutations. However, the missense variants exhibited very few differentially expressed genes (DEGs) when compared to each other. These data suggest that these activating GNAQ mutations differ in magnitude of activation but have similar downstream effects.

Bloom where you are planted: Hemangioma or malignancy?

Vascular anomalies comprise a spectrum of disorders characterized by the abnormal development or growth of blood and lymphatic vessels. These growths have unique features and diverse behaviors, mandating a multidisciplinary approach in their evaluation, diagnosis, and management. Here we describe the case of a male toddler presenting with an abdominal mass, originally treated as a metastatic retroperitoneal tumor, but subsequently felt to represent a vascular anomaly.

Introduction of Mutant GNAQ into Endothelial Cells Induces a Vascular Malformation Phenotype with Therapeutic Response to Imatinib

Simple Summary

Mutations in GNAQ underlie vascular malformations, including Sturge-Weber disease. In order to develop novel therapies for lesions with mutant GNAQ, we introduced mutant GNAQ into MS1 endothelial cells. Mutant GNAQ conferred a novel phenotype of progressive vascular malformations in mice. Chromatin analysis revealed upregulation of C-Kit in the vascular endothelial cells, and we found C-Kit to be highly expressed in Sturge-Weber disease. Given that imatinib is an FDA approved multikinase inhibitor that blocks C-Kit, we evaluated it in our mouse model, and showed that imatinib had activity against these vascular malformations. Repurposing imatinib should be evaluated in clinical trials, including Sturge-Weber disease.

Abstract

GNAQ is mutated in vascular and melanocytic lesions, including vascular malformations and nevi. No in vivo model of GNAQ activation in endothelial cells has previously been described. We introduce mutant GNAQ into a murine endothelial cell line, MS1. The resultant transduced cells exhibit a novel phenotype in vivo, with extensive vasoformative endothelial cells forming aberrant lumens similar to those seen in vascular malformations. ATAC-seq analysis reveals activation of c-Kit in the novel vascular malformations. We demonstrate that c-Kit is expressed in authentic human Sturge–Weber vascular malformations, indicating a novel druggable target for Sturge–Weber syndrome. Since c-Kit is targeted by the FDA-approved drug imatinib, we tested the ability of imatinib on the phenotype of the vascular malformations in vivo. Imatinib treated vascular malformations are significantly smaller and have decreased supporting stromal cells surrounding the lumen. Imatinib may be useful in the treatment of human vascular malformations that express c-Kit, including Sturge–Weber syndrome.

The genetics of vascular tumours: an update

Recent molecular advances have shed significant light on the classification of vascular tumours. Except for haemangiomas, vascular lesions remain difficult to diagnose, owing to their rarity and overlapping clinical, radiographic and histological features across malignancies. In particular, challenges still remain in the differential diagnosis of epithelioid vascular tumours, including epithelioid haemangioma and epithelioid haemangioendothelioma at the benign/low-grade end of the spectrum, and epithelioid angiosarcoma at the high-grade end. Historically, the classification of vascular tumours has been heavily dependent on the clinical setting and histological features, as traditional immunohistochemical markers across the group have often been non-discriminatory. The increased application of next-generation sequencing in clinical practice, in particular targeted RNA sequencing (such as Archer, Illumina), has led to numerous novel discoveries, mainly recurrent gene fusions (e.g. those involving FOS, FOSB, YAP1, and WWTR1), which have resulted in refined tumour classification and improved diagnostic reproducibility for vascular tumours. However, other molecular alterations besides fusions have been discovered in vascular tumours, including somatic mutations (e.g. involving GNA family and IDH genes) in a variety of haemangiomas, as well as copy number alterations in high-grade angiosarcomas (e.g. MYC amplifications). Moreover, the translation of these novel molecular abnormalities into diagnostic ancillary markers, either fluorescence in-situ hybridisation probes or surrogate immunohistochemical markers (FOSB, CAMTA1, YAP1, and MYC), has been remarkable. This review will focus on the latest molecular discoveries covering both benign and malignant vascular tumours, and will provide practical diagnostic algorithms, highlighting frequently encountered pitfalls and challenges in the diagnosis of vascular lesions.

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.

Molecular Diagnostics of Vascular Tumors of the Skin

In this article, the authors have reviewed all the recent news regarding how the discovery of some novel and recurrent molecular and genetic changes has modified the classification of some entities and have addressed to the description of new variants of vascular tumors. And even more important, the authors also reviewed on how these findings, in addition to gain insight into the tumoral biology, portend significant clinical consequences not only regarding to their diagnosis but also to their management and prognosis because some of these mutations are potential targets for treatment. The authors have also highlighted immunohistochemical markers can help us as a surrogate marker of those molecular alterations.

Detection of cryptogenic malignancies from metagenomic whole genome sequencing of body fluids

BACKGROUND

Metagenomic next-generation sequencing (mNGS) of body fluids is an emerging approach to identify occult pathogens in undiagnosed patients. We hypothesized that metagenomic testing can be simultaneously used to detect malignant neoplasms in addition to infectious pathogens.

METHODS

From two independent studies (n = 205), we used human data generated from a metagenomic sequencing pipeline to simultaneously screen for malignancies by copy number variation (CNV) detection. In the first case-control study, we analyzed body fluid samples (n = 124) from patients with a clinical diagnosis of either malignancy (positive cases, n = 65) or infection (negative controls, n = 59). In a second verification cohort, we analyzed a series of consecutive cases (n = 81) sent to cytology for malignancy workup that included malignant positives (n = 32), negatives (n = 18), or cases with an unclear gold standard (n = 31).

RESULTS

The overall CNV test sensitivity across all studies was 87% (55 of 63) in patients with malignancies confirmed by conventional cytology and/or flow cytometry testing and 68% (23 of 34) in patients who were ultimately diagnosed with cancer but negative by conventional testing. Specificity was 100% (95% CI 95-100%) with no false positives detected in 77 negative controls. In one example, a patient hospitalized with an unknown pulmonary illness had non-diagnostic lung biopsies, while CNVs implicating a malignancy were detectable from bronchoalveolar fluid.

CONCLUSIONS

Metagenomic sequencing of body fluids can be used to identify undetected malignant neoplasms through copy number variation detection. This study illustrates the potential clinical utility of a single metagenomic test to uncover the cause of undiagnosed acute illnesses due to cancer or infection using the same specimen.

GNA14, GNA11, and GNAQ Mutations Are Frequent in Benign but Not Malignant Cutaneous Vascular Tumors

Cutaneous vascular tumors consist of a heterogeneous group of benign proliferations, including a range of hemangiomas and vascular malformations, as well as heterogeneous groups of both borderline and malignant neoplasms such as Kaposi’s sarcoma and angiosarcomas. The genetics of these tumors have been assessed independently in smaller individual cohorts making comparisons difficult. In our study, we analyzed a representative cohort of benign vascular proliferations observed in a clinical routine setting as well as a selection of malignant vascular proliferations. Our cohort of 104 vascular proliferations including hemangiomas, malformations, angiosarcomas and Kaposi’s sarcoma were screened by targeted next-generation sequencing for activating genetic mutations known or assumed to be potentially relevant in vascular proliferations. An association analysis was performed for mutation status and clinico-pathological parameters. Frequent activating hotspot mutations in GNA genes, including GNA14 Q205, GNA11 and GNAQ Q209 were identified in 16 of 64 benign vascular tumors (25%). GNA gene mutations were particularly frequent (52%) in cherry (senile) hemangiomas (13 of 25). In angiosarcomas, activating RAS mutations (HRAS and NRAS) were identified in three samples (16%). No activating GNA or RAS gene mutations were identified in Kaposi’s sarcomas. Our study identifies GNA14 Q205, GNA11 and GNAQ Q209 mutations as being the most common and mutually exclusive mutations in benign hemangiomas. These mutations were not identified in malignant vascular tumors, which could be of potential diagnostic value in distinguishing these entities.

Updates from the 2020 World Health Organization Classification of Soft Tissue and Bone Tumours

The fifth edition of the World Health Organization (WHO) classification of soft tissue and bone tumours was published in May 2020. This 'Blue Book', which is also available digitally for the first time, incorporates an array of new information on these tumours, amassed in the 7 years since the previous edition. Major advances in molecular characterisation have driven further refinements in classification and the development of ancillary diagnostic tests, and have improved our understanding of disease pathogenesis. Several new entities are also included. This review summarises the main changes introduced in the 2020 WHO classification for each subcategory of soft tissue and bone tumours.

Recent updates in the diagnosis of soft tissue tumors: Newly described tumor entities, newer immunohistochemical and genetic markers, concepts, including "inter-tumor relationships"

During the last two decades, there have been significant strides in the diagnosis of soft tissue tumors, including identification of various tumor entities, newer immunohistochemical markers, and an increasing number of molecular signatures, defining certain tumors. Lately, there are certain emerging tumor entities, defined by their molecular features with an impact on treatment. At the same time, there is a certain degree of overlap in the expression of certain immunohistochemical antibody markers, as well as genetic markers, with certain gene rearrangements and chimeric fusions observed among completely different tumors. Moreover, a certain amount of clinicopathological, immunohistochemical, and molecular proximity has been unraveled among certain tumor types. Over the years, the World Health Organization (WHO) fascicles on tumors of soft tissue have succinctly brought out these aspects. The present review describes recent updates in the diagnosis of soft tissue tumors, including certain newly described tumor entities; emphasizing upon newer, specific immunohistochemical and molecular markers, along with concepts, regarding "intertumor relationships".

The 2020 WHO Classification of Tumors of Soft Tissue: Selected Changes and New Entities

Soft tissue tumors are a relatively rare and diagnostically challenging group of neoplasms that can have varying lines of differentiation. Accurate diagnosis is important for appropriate treatment and prognostication. In the 8 years since the publication of the 4th Edition of World Health Organization (WHO) classification of soft tissue tumors, significant advances have been made in our understanding of soft tissue tumor molecular biology and diagnostic criteria. The 5th Edition of the 2020 WHO classification of tumors of soft tissue and bone incorporated these changes. Classification of tumors, in general, but particularly in soft tissue tumors, is increasingly based on the molecular characteristics of tumor types. Understanding tumor molecular genetics improves diagnostic accuracy for tumors that have been difficult to classify on the basis of morphology alone, or that have overlapping morphologic features. In many large hospitals in the United States and Europe, molecular tests on soft tissue tumors are a routine part of diagnosis. Therefore, surgical pathologists should be familiar with newly emerging molecular genetic techniques in clinical settings. In the near future, molecular tests, particularly in soft tissue tumor diagnosis, will become as routine during diagnosis as immunohistochemistry is currently. This new edition provides an updated classification scheme and essential diagnostic criteria for soft tissue tumors. Newly recognized entities and subtypes of existing tumor types, several reclassified tumors, and newly defined molecular and genetic data have been incorporated. Herein, we summarize the updates in the WHO 5th Edition, focusing on major changes in each category of soft tissue tumor, and the newly described tumor entities and subtypes.

Functional characterization of uveal melanoma oncogenes

Uveal melanoma (UM) is a currently untreatable form of melanoma with a 50% mortality rate. Characterization of the essential signaling pathways driving this cancer is critical to develop target therapies. Activating mutations in the Gαq signaling pathway at the level of GNAQ, GNA11, or rarely CYSLTR2 or PLCβ4 are considered alterations driving proliferation in UM and several other neoplastic disorders. Here, we systematically examined the oncogenic signaling output of various mutations recurrently identified in human tumors. We demonstrate that CYSLTR2 → GNAQ/11 → PLCβ act in a linear signaling cascade that, via protein kinase C (PKC), activates in parallel the MAP-kinase and FAK/Yes-associated protein pathways. Using genetic ablation and pharmacological inhibition, we show that the PKC/RasGRP3/MAPK signaling branch is the essential component that drives the proliferation of UM. Only inhibition of the MAPK branch but not the FAK branch synergizes with inhibition of the proximal cascade, providing a blueprint for combination therapy. All oncogenic signaling could be extinguished by the novel GNAQ/11 inhibitor YM-254890, in all UM cells with driver mutation in the Gαq subunit or the upstream receptor. Our findings highlight the GNAQ/11 → PLCβ → PKC → MAPK pathway as the central signaling axis to be suppressed pharmacologically to treat for neoplastic disorders with Gαq pathway mutations.

Anastomosing hemangioma arising from the left renal vein: A case report

BACKGROUND

Anastomosing hemangioma (AH) is a rare subtype of benign hemangioma that is most commonly found in the genitourinary tract. Due to the lack of specific clinical and radiologic manifestations, it is easily misdiagnosed preoperatively. Here, we report a case of AH arising from the left renal vein that was discovered incidentally and confirmed pathologically, and then describe its imaging characteristics from a radiologic point of view and review its clinicopathologic features and treatment.

CASE SUMMARY

A 74-year-old woman was admitted to our department for a left retroperitoneal neoplasm measuring 2.6 cm × 2.0 cm. Her laboratory data showed no significant abnormalities. A non-contrast-enhanced computed tomography (CT) scan showed a heterogeneous density in the neoplasm. Non-contrast-enhanced magnetic resonance imaging (MRI) revealed a heterogeneous hypointensity on T1-weighed images and a heterogeneous hyperintensity on T2-weighed images. On contrast-enhanced CT and MRI scans, the neoplasm presented marked septal enhancement in the arterial phase and persistent enhancement in the portal phase, and its boundary with the left renal vein was ill-defined. Based on these clinical and radiological manifestations, the neoplasm was initially considered to be a neurogenic neoplasm in the left retroperitoneum. Finally, the neoplasm was completely resected and pathologically diagnosed as AH.

CONCLUSION

AH is an uncommon benign hemangioma. Preoperative misdiagnoses are common not only because of a lack of specific clinical and radiologic manifestations but also because clinicians lack vigilance and diagnostic experience in identifying AH. AH is not exclusive to the urogenital parenchyma. We report the first case of this neoplasm in the left renal vein. Recognition of this entity in the left renal vein can be helpful in its diagnosis and distinction from other neoplasms.

Congenital hepatic hemangiomas: Clinical, histologic, and genetic correlation

BACKGROUND

The guide for monitoring and treatment of congenital hepatic hemangiomas (CHH) will depend on the subtype and the postnatal clinical behavior. Our aim is to present a series of CHH and characterize its clinical, histologic and genetic correlation, compared to cutaneous congenital hemangiomas (CCH).

MATERIAL AND METHODS

A retrospective review of CHH patients diagnosed between 1991 and 2018 was performed. Clinical, morphological and histological data were analyzed and deep high-throughput sequencing was performed.

MAIN RESULTS

Sixteen patients with CHH were included. Five patients were followed up with serial ultrasounds while pharmacological treatment (corticosteroids and propranolol) was decided in five. Surgical resection was performed in five owing to hemorrhage and suspicion of malignancy, and the last patient underwent embolization. Histologic analysis was available in 7 patients and confirmed CHH, showing two different histological patterns that could be associated with the presence of somatic pathogenic variants in GNAQ and/or PIK3CA detected in the genetic testing. Review of 7 samples of CCH revealed some histologic differences compared to CHH.

CONCLUSION

CHH resemble its cutaneous homonym with similar clinical behavior. Histologic analysis can differentiate two subgroups while genetic testing can confirm mutations in GNAQ and in PIK3CA in a subset of CHH.

TYPE OF STUDY

Treatment study.

LEVEL OF EVIDENCE

IV.

Vascular tumors of the mediastinum

Vascular tumors represent only a sliver of all tumors affecting the mediastinum, but they pose diagnostic challenges due to significant overlap among entities, ever-evolving classification schemes, and the exquisite rarity of some of the entities not only in the mediastinum but in pathology practice as a whole. Most of the vascular tumors are better known to the practice of soft tissue pathology, from which some of the knowledge of clinical behavior can be extrapolated. For example, the stratification of epithelioid hemangioendothelioma (EHE) into two biologically separate categories has effectively translated from the somatic soft tissues to the thorax. For other entities, the effective validation of soft tissue parameters is hindered by the small numbers of reported mediastinal cases. Many of the treatment modalities have also transferred over, with the key differences resting on the difficulty in achieving complete surgical resection for mediastinal tumors as opposed to those in the somatic soft tissues. Accordingly, systemic drug therapies have emerged as attractive options for some of the mediastinal vascular tumors, such as kaposiform hemangioendothelioma (KHE) and Kaposi sarcoma (KS). The categories presented herein mirror the classification scheme set forth by the 5th Edition WHO Classification of Soft Tissue and Bone Tumors. This review focuses on the biologically aggressive vascular neoplasms while limiting discussion of the benign entities to relevant comparisons in the differential diagnoses. While distinguishing among the benign entities has academic importance, in practice, the stakes are far higher for diagnosing the biologically aggressive tumors given their marked heterogeneity in clinical outcomes. Practical advice for problem areas in pathology will be reviewed alongside tumor pathobiology, including the latest in molecular diagnostics.

Diffuse bone and soft tissue angiomatosis with GNAQ mutation

We describe a unique case of skeletal and extraskeletal angiomatosis complicated by Kasabach-Merritt syndrome. The patient was a 3-year-old boy, who presented with involvement of both femurs and left tibia, as well as with soft tissue lesions of the left thigh. At birth, multiple hemangiomas of the soft tissues of the frontal and parietal scalp had been identified, together with a space-occupying lesion of the lung. Histologically, the skeletal and soft tissue lesions consisted of a proliferation of thin-walled, dilated blood vessels, with an endothelial lining devoid of atypia and exhibiting immunoreactivity for CD31 and CD34, while podoplanin and GLUT1 were negative. Whole exome sequencing performed on samples from the lesion of the femur, the tibia and the skin of the thigh, showed a GNAQ (c.286A>T:p.T96S) variant in all specimens, that was confirmed with digital droplet PCR. This case expands the clinical and pathologic spectrum of vascular proliferations showing similar molecular biology, characterized by GNAQ, GNA11 or GNA14 mutations.

Anastomosing Hemangioma of the Breast: An Unusual Case at an Unusual Site

Anastomosing hemangioma (AH) is an unusual benign vascular lesion that commonly occurs in the kidney and genitourinary tract. We report a case of AH in a 49-year-old woman presenting as a mass in the breast, a site which, to the best of our knowledge, has not been previously documented in the English literature. Microscopic examination of the mass revealed a well-demarcated proliferation of anastomosing vascular spaces lined by bland endothelial cells, with focal hobnailing and scattered intravascular fibrin thrombi. No mitotic activity was observed and the Ki-67 proliferative index was low. These features were interpreted as AH, a lesion that may be difficult to distinguish from low-grade angiosarcoma or other benign vascular lesions of the breast which may demonstrate anastomosing channels. Due to the presence of atypical histologic features which can raise suspicion for angiosarcoma on biopsy, complete excision of these lesions is recommended for optimal treatment.

High frequency of GNA14, GNAQ, and GNA11 mutations in cherry hemangioma: a histopathological and molecular study of 85 cases indicating GNA14 as the most commonly mutated gene in vascular neoplasms

Cherry hemangioma is the most common hemangioma in adult life. Neoplastic and non-neoplastic theories had both been proposed for its pathogenesis, but its nature is still poorly understood. We noted a significant subset of anastomosing hemangiomas and congenital hemangiomas harbored a population of small capillaries surrounded by a perivascular hyaline layer, reminiscent of the vessels seen in cherry hemangioma. Both anastomosing hemangioma and congenital hemangioma harbor recurrent mutations in exon 5 of GNAQ and its paralogues. In this study, we analyzed 68 cherry hemangiomas and 17 cherry hemangioma-like hemangiomas exhibiting additional non-classical features including markedly dilated, cavernous vessels, and/or a deep component extending to the deep dermis. By Sanger sequencing, GNAQ, GNA11, and GNA14 exon 5 mutations were identified in 12, 4, and 32 cherry hemangiomas, respectively, and 5, 3, and 3 cherry hemangioma-like hemangiomas, respectively. MassARRAY analysis detected mutations (including exon 2 GNAQ^G48V mutations) in additional 8 cherry hemangiomas and 3 cherry hemangioma-like hemangiomas. Overall, the cherry hemangiomas and cherry hemangioma-like hemangiomas had equal GNA mutation rates (82%), and GNA14 and GNAQ mutations were present in approximately half of cherry hemangiomas and cherry hemangioma-like hemangiomas, respectively. All mutations were mutually exclusive. KRAS^G12V mutation was also detected in one cherry hemangioma-like hemangioma without GNA mutations. In summary, our study demonstrated recurrent GNA14/GNAQ/GNA11 mutations were present in the majority of this very common hemangioma and established its neoplastic nature. Our results also expanded the morphological spectrum of GNA-mutated hemangiomas to include tumors composed of cavernous-like vessels and indicated GNA14 was the most commonly mutated gene in vascular tumors.

Thrombotic Hemangioma With Organizing/Anastomosing Features: Expanding the Spectrum of GNA-mutated Hemangiomas With a Predilection for the Skin of the Lower Abdominal Regions

In this study, we aimed to present the clinicopathologic and molecular features of a distinct group of hemangioma with GNA mutations that exhibited prominent thrombosis and organization changes with florid intravascular endothelial cell proliferation that we provisionally termed "thrombotic hemangioma with organizing/anastomosing features." Twenty-six cases were included. No sex predilection was seen (male:female=13:13). Patients' age ranged from 17 to 89 years (median: 51 y). All but 1 occurred in the skin whereas the remaining tumor involved the neck soft tissue. Remarkably, the majority (18) occurred in the lower abdominal/inguinal regions. Histologically, thrombotic hemangioma with organizing/anastomosing features were circumscribed tumors composed of variably sized and congested thin-walled vessels. The most striking features were prominent thrombosis and organization with florid intravascular endothelial cell proliferation. The proliferating endothelial cells exhibit a streaming pattern with focal anastomosing-like feature resembling anastomosing hemangioma. The stroma was sclerotic or hyalinized but could also be myxoid/edematous. Other features included vessels with nuclear hobnailing and perivascular hyalinization, cherry hemangioma-like component, cavernous-like or sinusoidal hemangioma-like areas, Masson hemangioma-like feature, and spindle cell fascicular pattern. Mitotic activity was usually low and nuclei were bland but 2 tumors exhibited moderate nuclear atypia and higher mitotic activity. Extramedullary hematopoiesis and hyaline globules were not identified. Genetically, by Sanger sequencing and MassARRAY analysis, mutually exclusive GNAQ, GNA11, and GNA14 exon 5 mutations were identified in 15, 5, and 2 tumors, respectively, with a combined mutation rate of 85% (22/26). In conclusion, we described a distinct group of hemangioma and expanded the clinicopathologic features of GNA-mutated hemangiomas.

Use of Targeted Next-Generation Sequencing to Identify Activating Hot Spot Mutations in Cherry Angiomas

Importance

Shared gene variants in benign-malignant process pairs, such as BRAF mutations common to benign nevi and melanoma, are associated with differing phenotypic manifestations. Study of gene mechanisms underlying cherry angioma may uncover previously unknown disease relationships.

Objective

To identify somatic mutations present in cherry angioma specimens by using targeted next-generation sequencing.

Design, Setting, and Participants

In a single-center case series, 10 formalin-fixed, paraffin-embedded cherry angioma specimens from biopsies performed at Massachusetts General Hospital in Boston from July 10, 2016, to January 23, 2018, were obtained and underwent sequencing across a panel of 323 genes most relevant to cancer. Somatic mutations were curated by excluding variants that were presumed to be germline or of low mapping quality.

Main Outcomes and Measures

Identification of somatic mutations associated with cherry angiomas.

Results

In 10 cherry angioma tissue samples originating from 6 female and 4 male patients with a median (range) age of 54 (26-79) years, 5 samples (50%) revealed somatic missense mutations in GNAQ (Q209H, Q209R, and R183G) and GNA11 (Q209H). Individually, these mutational hot spots are known to be involved in entities that include congenital and anastomosing hemangiomas, hepatic small-vessel neoplasms (Q209), port-wine stains, and Sturge-Weber syndrome (R183). Both hot spots are associated with blue nevi, melanoma associated with blue nevus, and uveal melanoma.

Conclusions and Relevance

In this case series study, the high prevalence of 5 known genetic drivers within the benign cherry angioma entity appears to support the context-dependent role of gene alterations in both benign and malignant proliferations from various cellular origins.

Frequent GNAQ and GNA14 Mutations in Hepatic Small Vessel Neoplasm

Hepatic small vessel neoplasm (HSVN) is a recently described infiltrative vascular neoplasm of the liver, composed of small vessels. Although the infiltrative nature can mimic angiosarcoma, HSVN are thought to be benign or low-grade neoplasms because they lack cytologic atypia and increased proliferation. To characterize the molecular pathogenesis of HSVN, we performed both targeted panel sequencing and exome sequencing on 18 benign or low-grade vascular neoplasms in the liver including 8 HSVN, 6 classic cavernous hemangioma (CH), and 4 variant lesions (VL) with overlapping features between HSVN and CH. All 18 lesions had simple genomes without copy number alterations. In total, 75% (6/8) of HSVN demonstrated known activating hotspot mutations in GNAQ (2/8, p.Q209H) or GNA14 (4/8, p.Q205L), and the remaining 2 had the same missense mutation in GNAQ, p.G48L, which has not been previously described. 25% (1/4) of VL had a hotspot GNAQ p.Q209H mutation and another VL had a GNAQ p.G48L mutation. Known pathogenic mutations were not identified in any of the 6 CH. These data suggest that HSVN share a similar molecular biology to several other vascular lesions (congenital hemangioma, tufted angioma, anastomosing hemangioma, lobular capillary hemangioma, and kaposiform hemangioendothelioma) recently reported to have GNAQ, GNA11, or GNA14 mutations.

Left Atrial Anastomosing Hemangioma Causing Recurrent Pericardial Effusion

We report an extremely rare tumor in an adult patient who presented with recurrent pericardial effusion. The mass was an extracardiac tumor on the left atrial roof, which was excised by open heart surgery. Histologic examination confirmed a cardiac anastomosing hemangioma.

GNAQ Q209R Mutations Are Highly Specific for Circumscribed Choroidal Hemangioma

Several tumors, including uveal melanoma, show somatic mutations of GNAQ/GNA11. Circumscribed choroidal hemangioma is a benign tumor that becomes symptomatic in adulthood. In some patients, morphologic examination of biopsies is required for differential diagnosis between amelanotic choroidal melanoma and circumscribed choroidal hemangioma. Here, we report the results of GNAQ/GNA11 mutation analysis in samples from circumscribed choroidal hemangioma. Deep amplicon sequencing (Illumina MiSeq, San Diego, CA, USA) of positions R183 and Q209 of GNAQ and GNA11 in tissue samples from 33 patients with histologically diagnosed circumscribed choroidal hemangioma. All patients underwent biopsy or enucleation at our clinic between 2008 and 2018. To enable detection of variant alleles at low fractions, read depth exceeded 15,000-fold. DNA for genetic analysis was prepared from either snap-frozen (n = 22) or FFPE (n = 11) tissue samples. Samples from 28/33 patients (85%) showed a somatic missense mutation of GNAQ (c.626 A > G) predicted to result in p.Q209R. Variant allele fraction was variable (range 2.3% to 28%). Variants of GNAQ resulting in p.Q209 are characteristic for circumscribed choroidal hemangiomas. It appears that the GNAQ mutation spectrum in this tumor is narrow, possibly restricted to p.Q209R. Moreover, the spectrum is distinct from that of uveal melanoma, in which alterations resulting in p.Q209R are very rare.

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.

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.