Retroperitoneal peripheral hemangioblastoma: a case report and review of the literature

Uncommon Tumors of the Lung: Recently Described and Rediscovered Tumors

CONTEXT.—

The great majority of primary pulmonary neoplasms are represented by non-small cell carcinomas-adenocarcinoma and squamous cell carcinoma. In addition, there is another group of neoplasms such as those of neuroendocrine origin that also represent a meaningful subset of primary lung neoplasms. Basically, any other tumor that is not in these groups of tumors may represent an unusual lung neoplasm.

OBJECTIVE.—

To highlight more recently described unusual tumoral entities that may represent a challenge in diagnosis and that require awareness of their existence.

DATA SOURCES.—

This is a review of 3 different entities: bronchiolar adenoma, adenofibroma, and hemangioblastoma-like clear cell stromal tumor. These tumoral conditions are rare, and a review of the literature is presented. The most relevant morphologic, immunohistochemical, and molecular aspects of bronchiolar adenoma, adenofibroma, and hemangioblastoma-like clear cell stromal tumor are presented. The difficulty of arriving at an unequivocal diagnosis in small biopsies is highlighted.

CONCLUSIONS.—

The 3 entities represent uncommon tumors occurring primarily in the lung and a diagnostic challenge not only in biopsy specimens but also often in surgically resected specimens. The use of immunohistochemical stains and in some cases of molecular diagnostics is of aid in arriving at final interpretation.

A rare case of a sporadic retroperitoneal hemangioblastoma

Hemangioblastoma is a rare, benign, and morphologically distinctive tumor. In most cases, the tumor involves the central nervous system. Extraneural occurrences are rare, with just a few reports of hemangioblastoma situated outside of neural tissue, such as the retroperitoneum. We report a case of sporadic retroperitoneal hemangioblastoma in an 87-year-old male patient, diagnosed as an incidental finding in a CT scan performed because of kidney stone disease. The CT scan showed a mass in the retroperitoneum posterior to the inferior vena cava. The patient reported no remarkable symptoms. We describe our path to diagnosis, the possible differential diagnosis for retroperitoneal masses, and the histopathologic features of the tumor. There are <250 reported extra neuraxial hemangioblastomas and just 14 reported cases situated outside of the neural tissue. Our case is the eighth case report of a hemangioblastoma arising from the soft tissue of the retroperitoneum.

Adrenal hemangioblastoma

Hemangioblastoma (HB) is a rare benign tumor that most commonly occurs in the cerebellum. HB is composed of neoplastic stromal cells and abundant small vessels. However, the exact origin of stromal cells is controversial. Extraneural HBs have been reported in a small series, and peripheral HBs arising in the adrenal gland are extremely rare. Herein, we report a case of sporadic adrenal HB in a 54-year-old woman. The tumor was a well-circumscribed, yellow mass measuring 4.2 cm in diameter. Histologically, the tumor was composed of small blood vessels and vacuolated stromal cells with clear cytoplasm. On immunohistochemical stain, the stromal cells were positive for S-100 protein, neuron-specific enolase, and synaptophysin. The tumor did not reveal mutation of VHL alleles. We herein present a case of HB of the adrenal gland and review of the literature.

Hemangioblastoma-like Clear Cell Stromal Tumor of the Lung: A Clinicopathologic and Immunohistochemical Study of 5 Cases

Five cases of an unusual primary benign stromal tumor designated as hemangioblastoma-like clear cell stromal tumor of the lung are presented. The patients are 4 women and 1 man between the ages of 39 and 52 years of age (average: 45.5 y). The patients presented with nonspecific symptoms of cough, chest pain, or dyspnea. None of the patients had any prior history of malignancy or tumor elsewhere. Diagnostic imaging showed the presence of an intrapulmonary tumor. Lobectomy was performed in all 5 patients. Grossly, the tumors were well-demarcated but not encapsulated with focal areas of hemorrhage without necrosis. Histologically, low power examination showed a cellular proliferation alternating with discrete dilated vessels reminiscent of a vascular neoplasm. Higher magnification showed medium-sized cells with clear cytoplasm arranged in sheets and cords. Mitotic activity and marked cellular atypia were not present. A wide panel of immunohistochemical studies was performed including epithelial, neural, muscle, vascular, and neuroendocrine markers, all of which showed negative staining. Tumor cells showed positive staining for vimentin. In 2 cases, fluorescence in situ hybridization for the solitary fibrous tumor was performed and was negative. Clinical follow-up in 3 patients showed no evidence of recurrence. The cases herein presented highlight an unusual benign stromal tumor of the lung, which needs to be considered in the differential diagnosis of tumors with a clear cell and vascular appearance.

Renal Cell Carcinoma With Hemangioma-Like Features: Diagnostic Implications and Review of the Literature

Renal cell carcinoma (RCC) with clear cell morphology may show a prominent delicate vascularity. In this article, we report the morphologic and immunohistochemical features of a clear cell papillary RCC mimicking hemangioblastoma and a clear cell RCC mimicking hemangioma. Case 1 showed tubular and papillary growth of clear cells with distinctive areas of capillary proliferation and admixed stromal-like cells resembling a hemangioblastoma. Case 2 consisted of homogeneously delicate microvascular proliferations resembling a capillary hemangioma with scattered inconspicuous clear cells. The clear cells of Case 1 were PAX8(+), CK7(diffuse+), CA9(diffuse+, cup-shaped), and inhibin A(−). The hemangioblastoma-like areas were PAX8(+), CK7(−), CA9(diffuse+), and inhibin A(diffuse+). Case 2 showed PAX8(+), CK7(−), and CA9(diffuse+). They can be diagnostically challenging, and it is important to recognize that a pure hemangioma or hemangioblastoma of the kidneys is very rare, and that RCCs with clear cell morphology rarely exhibit hemangioma-like characteristics.

Extraneuraxial hemangioblastoma: A clinicopathologic study of 10 cases with molecular analysis of the VHL gene

Less than 250 extraneuraxial hemangioblastomas occurring in paraneuraxial or peripheral sites have been reported to date, sporadically or in the setting of von Hippel-Lindau disease. Seventeen such cases underwent molecular genetic analysis, using either the patient's peripheral blood in 9 cases or paraffin embedded tumor tissue in the rest. VHL gene mutations were documented in 3/9 cases in which DNA from peripheral blood lymphocytes was used, all with clinically manifest von Hippel-Lindau disease; instead, no VHL gene alterations were found in all of the 8 cases with sporadic extraneuraxial hemangioblastoma in which DNA from tumor tissue was analyzed. Our aim is to investigate the molecular genetic profile of the VHL gene in extraneuraxial hemangioblastoma using paraffin embedded tumor tissues. The clinical features, histopathology, and molecular investigations of 10 extraneuraxial hemangioblastomas (7 females, 3 males; median age: 47 years) are presented herein. The histopathologic diagnosis was supported by immunohistochemistry (10/10) and electron microscopy (4/10). Molecular genetic analysis was conducted (10/10) for VHL gene mutations, LOH, and gene promoter methylation. Two of the present cases were already published with only limited or no molecular investigations. Four tumors of the present series were paraneuraxial, and 6 peripheral (2 involved soft tissues, and 4 the kidney). One tumor was von Hippel-Lindau disease-associated, 1 was classified as "hemangioblastoma-only VHLD", 7 were sporadic, and one was unknown. All were histopathologically analogous to their counterpart located inside the central nervous system. Immunophenotypically, all tumors expressed vimentin, S-100, NSE, and alpha-inhibin (10/10). Ultrastructurally, unbound lipid droplets filled the cytoplasms of the stromal cells. Molecular analysis revealed 3 inactivating mutations (1 germline, two somatic) in the coding sequence of the VHL gene in 2 different extraneuraxial hemangioblastomas, and LOH in 4 (two as a double hit), all non-renal extraneuraxial hemangioblastomas. Methylation analysis failed to disclose promoter methylation in any case. In conclusion, we report eight new cases from the wide category of extraneuraxial hemangioblastomas (4 paraneuraxial, and 4 renal), one of which was von Hippel-Lindau disease-associated and 7 sporadic. VHL gene alterations were found not only in the von Hippel-Lindau disease-associated tumor, but - for the first time - also in 3 sporadic ones, two of which with novel mutations.

Extraneuraxial Hemangioblastoma: Clinicopathologic Features and Review of the Literature

Extraneuraxial hemangioblastoma occurs in nervous paraneuraxial structures, somatic tissues, and visceral organs, as part of von Hippel-Lindau disease (VHLD) or in sporadic cases. The VHL gene plausibly plays a key role in the initiation and tumorigenesis of both central nervous system and extraneuraxial hemangioblastoma, therefore, the underlying molecular and genetic mechanisms of the tumor growth are initially reviewed. The clinical criteria for the diagnosis of VHLD are summarized, with emphasis on the distinction of sporadic hemangioblastoma from the form fruste of VHLD (eg, hemangioblastoma-only VHLD). The world literature on the topic of extraneuraxial hemangioblastomas has been comprehensively reviewed with ∼200 cases reported to date: up to 140 paraneuraxial, mostly of proximal spinal nerve roots, and 65 peripheral, 15 of soft tissue, 6 peripheral nerve, 5 bone, and 39 of internal viscera, including 26 renal and 13 nonrenal. A handful of possible yet uncertain cases from older literature are not included in this review. The clinicopathologic features of extraneuraxial hemangioblastoma are selectively presented by anatomic site of origin, and the differential diagnosis is emphasized in these subsets. Reference is made also to 10 of the authors' personal cases of extraneuraxial hemangioblastomas, which include 4 paraneuraxial and 6 peripheral (2 soft tissue hemangioblastoma and 4 renal).

Sporadic Retroperitoneal Hemangioblastoma: Report of a Case and Review of the Literature

We report a case of sporadic isolated hemangioblastoma arising from the retroperitoneum and provide a review of the scarce literature regarding this very rare tumor. Furthermore, we thoroughly describe the pathologic features and the broad differential diagnosis that should always be included in the study of any retroperitoneal soft tissue mass to arrive at the final diagnosis.

Extraneural hemangioblastoma of the kidney: the challenge for clinicopathological diagnosis

Background

Hemangioblastoma is a benign cerebellar tumour which may occur as a sporadic entity or in association with von Hippel-Lindau (VHL) disease in approximately 25% of cases. Renal hemangioblastoma (RH) is an extremely rare and newly recognised tumour. Here, we describe five cases of RH, one discovered by CT in an accident and the other four detected during routine examinations.

Methods

Five cases of renal hemangioblastoma retrieved from the Department of Pathology, Fudan University Shanghai Cancer Center were studied and the literatures were reviewed. Immunohistochemistry was used to differentiate and confirm this tumour.

Results

Pathological examination following tumour resection revealed RH in all cases, the first patient was also diagnosed with renal cell carcinoma (RCC), suggesting the possibility of VHL syndrome, but PCR sequencing analysis of the VHL gene confirmed no mutation in any of the three exons, implying sporadic disease .Histologically, the tumours were circumscribed, composed of sheets of oval or polygonal cells and a prominent vascular network. Tumour cells had pleomorphic nuclei, but mitotic figures were rare. The diagnosis of hemangioblastoma was confirmed by immunohistochemistry.

Conclusions

RH is very rare and is challenging to differentially diagnose. Distinguishing RCC and RH is difficult and each has a different prognosis, so differentiating between them is essential for avoiding over-diagnosis and unnecessary treatment.

Primary gastric hemangioblastoma: report of a case

Capillary hemangioblastoma (CHB) is a benign, highly vascularized tumor that generally occurs in central nervous system either in the setting of von Hippel-Lindau (VHL) disease or, more often, as a solitary sporadic lesion that is increasingly recognized in extraneural sites. We present the case of a 18 year-old man with abdominal pain, nausea and hematemesis, the endoscopy showed polypoid tumor bleeding of 5 cm in gastric antrum. The patients had not signs of VHL disease and was subjected to subtotal gastrectomy and referred to our institution. To our knowledge this is the first reported case of CHB occurring in stomach.

Hemangioblastoma in the lung: metastatic or primary lesions?

Hemangioblastoma primarily occurs in the CNS, most commonly in the posterior fossa. Extracranial locations are less common, and metastatic tumor involving the lung is exceedingly rare with only three cases previously reported. Two were autopsy studies in patients who died of complications of the CNS hemangioblastomas in 1943 and 1981, and the third was mentioned in a case report addendum providing follow-up information on hepatic hemangioblastoma in 1991. We report a case of a 48-year-old man who presented with multiple lung nodules treated by surgical excision. Pathological study revealed features classic for hemangioblastoma. The patient had a remote history of hemangioblastomas having been excised from the posterior fossa 7 and 20 years previously. This report details a fourth case of metastatic pulmonary hemangioblastoma. It is the first report on surgically resected hemangioblastomas from the lung of a living patient with histological and immunohistochemical characterization.

PAX8 expression in sporadic hemangioblastoma of the kidney supports a primary renal cell lineage: implications for differential diagnosis

Hemangioblastoma is a benign, morphologically distinctive neoplasm of disputed histogenesis that typically occurs in the central nervous system either in the setting of von Hippel-Lindau disease or more often sporadically. Extraneural hemangioblastoma is exceptional and raises a challenging differential diagnosis. Herein, we report a primary renal hemangioblastoma occurring in 51-year-old woman without stigmata of von Hippel-Lindau disease. Histologically, the tumor was composed of sheets of polygonal epithelioid stromal cells with ample pale or eosinophilic, vacuolated cytoplasm in an arborizing capillary network. Tumor cells showed variable nuclear pleomorphism, intranuclear cytoplasmic invaginations, scattered hyaline globules, and psammoma-like calcifications. Some areas showed branching hemangiopericytoma-like vessels with tumor cells radiating from the wall, while other areas were edematous and hyalinized with sparse stromal cells and abundant reticular vessels. Immunohistochemically, the tumor cells reacted strongly and diffusely with antibodies to PAX8, CD10, α-inhibin, S100 protein, neuron-specific enolase, and vimentin, and they showed focal positivity with antibodies to epithelial membrane antigen and AE1/AE3. Tumor cells were negative for CK7, CK8/18, RCC antigen, synaptophysin, chromogranin, c-kit, D2-40, HMB45, melan-A, cathepsin K, SMA, desmin, CD31, CD34, and estrogen and progesterone receptors. Positive immunoreactivity for PAX8 is unexpected and contrasts to central nervous system (CNS) hemangioblastomas, which are essentially always negative for PAX8. This novel finding adds support to the hypothesis that the immunoprofile of extraneural hemangioblastoma varies with site of origin, perhaps as a result of tumor cell lineage and retention of organ-specific markers or acquisition of site-specific antigens due to local factors.

Hemangioblastoma of the gastrointestinal tract: a first case

We present the first documented case of hemangioblastoma located in the left colon. A 75-year-old woman undergoing adjuvant chemotherapy for breast cancer experienced rectal bleeding. Colonoscopy revealed a roundish mass covered with normal mucosa in the sigmoid colon. Endoscopic ultrasound showed an isoechoic lesion originating from the third layer of the intestinal wall; underlying layers were normal. Endoscopic ultrasound features were not suggestive of either cancer or malignant stromal tumor. Left hemicolectomy was subsequently performed due to repeated episodes of lower gastrointestinal bleeding. Grossly, a circumscribed submucosal yellowish nodule (13 mm) was observed, which was not attached to any peripheral nerve. Histologically, the lesion was composed of large, atypical cells traversed by a network of blood vessels. Immunohistochemically, the cells showed positivity for inhibin and NSE and weak positivity for S-100. A diagnosis of hemangioblastoma was made. This case highlights that hemangioblastoma of the gastrointestinal tract can also occur.

Hemangioblastoma-like clear cell stromal tumor of the lung

The authors report 2 cases of an apparently unpublished stromal tumor of the lung characterized by a predominantly endobronchial growth pattern and benign-appearing clear cells. Both tumors were discovered incidentally in adult patients during routine workups for other medical reasons and treated with lobectomy. On gross inspection there was no evidence of infiltration of the adjacent lung tissue. Microscopically, both lesions featured monotonous oval-shaped to spindle-shaped cells growing in a vaguely nested pattern. The cytoplasm was slightly vacuolated or granular. In 1 case there was a variable admixture with mature fat. Immunohistochemistry was negative for markers of epithelial and stromal differentiation except for vimentin. A focal reaction for CD34 was seen in 1 case. No mutation of coding sequence of VHL gene was seen in one case. Medical follow-up at 1 year was negative for tumor recurrence or metastases. The broad differential diagnosis within the spectrum of stromal lung tumor is discussed. Owing to distinctive microscopic features such as the nesting of clear cells within a vascularized background, both tumors appeared similar to hemangioblastoma, although the expected immunohistochemical profile of the latter was not fully expressed. Because of pattern of growth seen in both lesions we believe that the appellation of endobronchial, hemangioblastoma-like clear cell stromal tumor may be provisionally designed.

Soft-tissue hemangioblastoma of the retroperitoneum: a case study and review of the literature

A 71-year-old woman was found to have a solid retroperitoneal mass measuring 7 x 6 cm on a computed tomography scan. The tumor was not connected to the spinal cord or large nerves. It was resected and showed the typical histology of hemangioblastoma, that is, numerous capillaries and stromal cells with focal cytoplasmic vacuolization. Immunohistochemical study revealed that the tumor stromal cells were positive for S-100 protein, neuron-specific enolase, and inhibin-α, supporting the diagnosis. In addition, the tumor cells labeled for carbonic anhydrase IX and brachyury. The diffuse strong carbonic anhydrase IX expression suggested that soft-tissue hemangioblastoma may share with central nervous system hemangioblastoma the tumorigenic mechanism involving the von Hippel-Lindau gene product and hypoxia-inducible factor. The brachyury expression observed in this case, albeit focal and weak, may implicate embryonic hemangioblasts as a potential line of differentiation, as was proposed in central nervous system hemangioblastoma. The patient is well 4 years after the surgery without any recurrence. A review of the literature revealed that soft-tissue hemangioblastoma is typically a solid tumor found in older females and often involves the retroperitoneum/pelvis.

Sporadic hemangioblastoma of the kidney: an underrecognized pseudomalignant tumor?

Hemangioblastoma is a benign tumor that can occur sporadically, or in association with von Hippel-Lindau disease in approximately one-quarter of the cases. Only exceptionally does it occur outside the central nervous system. This report describes 2 cases of sporadic renal hemangioblastoma, with 1 patient presenting with hematuria and polycythemia, and the other low back pain. Histologically, the tumors were circumscribed, and composed of sheets of large polygonal cells traversed by arborizing thin-walled blood vessels. Many of the tumor cells showed pleomorphic nuclei, but the mitotic figures were rare. The cytoplasm was eosinophilic, and occasionally finely vacuolated indicating the presence of lipid. The diagnosis of hemangioblastoma was confirmed by negative immunostaining for cytokeratin, and positive staining for α-inhibin, S100, and neuron-specific enolase. This benign neoplasm which can be mistaken for various malignancies such as renal cell carcinoma, epithelioid angiomyolipoma, adrenal cortical carcinoma, and paraganglioma, deserves wider recognition for its occurrence as a primary renal tumor.

Primary Capillary Hemangioblastoma of Bone: Report of a Case Arising in the Sacrum

Capillary hemangioblastoma (CHB) is a benign, highly vascularized tumor that generally occurs in the central nervous system either in the setting of von Hippel-Lindau (VHL) disease or, more often, as a solitary sporadic lesion that is increasingly recognized in extraneural sites. We present the case of a 72-year-old woman with low back pain and a well-demarcated lytic lesion of the sacrum, which at histological and ultrastructural examination was indistinguishable from central nervous system CHB. The patient had no signs of VHL disease and died of another cause with no evidence of disease 57 months after curettage of the lesion. To our knowledge, this is the second case of CHB reported to occur in bone.

Extraneural hemangioblastoma: a report of 5 cases

Hemangioblastoma is a morphologically distinctive tumor that can occur sporadically or in association with von Hippel-Lindau disease, and which involves the central nervous system in the majority of the cases. Rare occurrences of hemangioblastoma in peripheral nerves and extraneural tissues have been reported. The histogenesis of this tumor remains uncertain. Various cell lineages such as vascular, glial, neural, fibrohistiocytic, and smooth muscle/myofibroblastic have been proposed for the so-called stromal cells, which are thought to represent the neoplastic component of these lesions. We report on 5 cases of hemangioblastoma arising in extraneural tissues. Two of the tumors were located in the presacral region, and one each in the maxilla, kidney, and adrenal glands. All 5 cases were morphologically indistinguishable from central nervous system hemangioblastoma. The existence of these cases suggests that the "stromal" cells of hemangioblastoma can demonstrate a variety of mature specific lineages, such as smooth muscle/myofibroblastic, or neuroendocrine, depending on the location and possibly the microenvironment.

Central nervous system capillary haemangioblastoma: the pathologist's viewpoint

Haemangioblastomas are rare neoplasms of uncertain histogenesis. They represent 1.5-2.5% of intracranial tumours. While the cerebellum is by far the most frequent site, these lesions also tend to occur in the medulla and spinal cord. Most haemangioblastomas are sporadic but up to one quarter are associated with Von Hippel-Lindau disease (VHL). Although a fairly good number of haemangioblastomas were reported, a lack of side-by-side analysis of these reports has resulted in tentative conclusions that merely offer a first glimpse at their clinicopathologic diversity and histogenesis. To remedy this issue, this study presents a literature review concerning these lesions. Medline literature including both relevant monographs and clinicopathological case series. Haemangioblastomas occur either as a part of VHL disease (25-30%, inherited mutation of VHL gene on 3p25-26 chromosome) or as sporadic tumours (often with somatic mutation of VHL gene). They have diverse clinicopathologic presentations with cerebellar lesions having a better prognosis than their brainstem counterparts. Immunostaining is important for separation of haemangioblastomas from other tumours with similar histology. The rich vascularity of haemangioblastomas is due to overexpression of vascular endothelial growth factors. Moreover, 'stromal' cells represent the neoplastic cells of haemangioblastomas and are capable of forming blood islands with extramedullary haematopoiesis.

Capillary hemangioblastoma of soft tissue: report of a case and review of the literature

Capillary hemangioblastoma (CH) is a tumor of unknown histogenesis that arises primarily in the posterior cranial fossa, either as a sporadic event or in association with von Hippel-Lindau disease. To date, only 6 examples of a tumor with morphological features of CH arising in the somatic soft tissues have been documented in case reports and small series, and 3 of these tumors were associated with a peripheral nerve. Herein, we report a case of CH arising in the gastrocnemius muscle and not associated with a peripheral nerve in a 53-year-old woman with no clinical stigmata or family history of von Hippel-Lindau disease.

[Cerebellar hemangioblastomas--a study of the immunoprofile of neoplastic stromal component]

BACKGROUND

Central nervous system hemangioblastomas (HBs) are uncommon, highly vascularized tumors that are predominantly found in the cerebellum. They occur sporadically or in association with von Hippel-Lindau (VHL) disease. HBs are of unknown histogenesis, and the origin of stromal cells is still a subject of debate. The aim of this study was to investigate the immunoprofile of neoplastic stromal component, and to determine whether the profile of the expression of immunomarkers used can contribute to the elucidation of the histogenesis of HBs.

METHODS

A series of eight cerebellar HBs were histochemically examined for the detection of mast cells and immunohistochemically for the expression of factor VIII-related antigen (FVIII-RAg), CD34, vimentin, factor XIIIa (FXIIIa), S-100 protein, glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), neurofilaments (NF), synaptophysin, chromogranin, and somatostatin.

RESULTS

Mast cells were present in all hemangioblastomas, and were particularly abundant in one tumor. Immunohistochemically, intense reactivity for vimentin and NSE in the stromal cells was constantly seen. Immunoreactivity with S-100 protein and FXIIIa was variable, but generally many HBs stromal cells were negative for these markers. However, stromal cells were uniformly negative for FVIII-RAg in all HBs investigated. They were negative for CD34, GFAP, NF, synaptophysin, chromogranin, as well as somatostatin. GFAP-positivity of the occasional stromal type cells, located only peripherally, was interpreted as "pseudopositivity".

CONCLUSION

The immunoprofile of neoplastic stromal component in this study suggested a possible origin from undifferentiated multipotential mesenchymal cells. High expression of NSE (glycolytic and hypoxia-inducible enzyme) in the HBs stromal cells might be related to the loss of the VHL protein function.

Primary capillary hemangioblastoma of peripheral soft tissues

A case of capillary hemangioblastoma located in the peripheral soft tissue of the inner ankle in a 74-year-old woman is presented. The tumor was an unencapsulated but sharply circumscribed nodule 2.5 cm in size, of a yellow-white color. It showed reddish-brown spots with small cysts up to 2 mm filled with blood. Grossly the tumor was not attached to any peripheral nerve. Signs of von Hippel-Lindau's disease were excluded by thorough clinical evaluation. No additional tumor or erythrocytosis was found in the patient clinically. Immunohistochemically, the tumor stromal cell reacted strongly with antibodies to S-100 protein, NSE, and calponin and they were negative with antibodies to GFAP, CD34, CD31, cytokeratins, actin, desmin, EMA, and HMB-45. Endothelium of the capillaries reacted positively with antibodies to CD31, CD34, and Factor VIII-related protein. Capillary pericytes were actin-positive. All cells of the tumor stained positively with antibody to vimentin. MIB1 antibody reacted only in very few cells (<1%). Ultrastructurally, the stromal cells contained electron-lucent cytoplasm with lipid droplets, a small amount of rough endoplasmic reticulum, and glycogen particles. No electron-dense structures typical of secretory granules were seen in the stromal cells. No mutation of coding sequence of VHL gene was found.