A hepatic tumor associated with bilateral renal angiomyolipomas: A variant of angiomyolipoma?

Angiomyolipoma is usually derived from the kidney and composed of well developed vessels, smooth muscle and fat tissue. The liver is the only extra-renal site of angiomyolipoma. A peculiar type of hepatic tumor accompanied by bilateral renal angiomyolipomas is reported here. The tumor was mostly composed of large epithelioid cells and a small part of hyalinized large vessels and foam cell infiltration. Mature adipose tissue was absolutely absent. Epithelioid tumor cells arranged in an alveolar pattern had abundant glycogen and some diastase-resistant periodic acid-Schiff granules without obvious crystals. Immunohistochemical studies revealed that the epithelioid cells were positive for melanoma specific antibody (HMB-45), S-100 protein, aromatic L-amino acid decarboxylase and focally a-smooth muscle actin. Many melanosome- or premelanosome-like, electron-dense granules were observed in these cells. Thus, these cells were characterized by differentiation to both immature melanocytes and smooth muscle ceils. These epithelioid cells were similar to some cells in the renal angiomyolipomas of the same patient. The hepatic tumor was considered to be a result of monotonous proliferation of the epithelioid cells seen in renal angiomyolipoma. Differential diagnosis of this tumor was discussed.     

Renal angiomyolipoma: further immunophenotypic characterization of an expanding morphologic spectrum

BACKGROUND: Renal angiomyolipoma is a benign tumor histologically characterized by proliferation of spindle cells, epithelioid cells, and adipocytic cells in concert with many thick-walled blood vessels. To add further diagnostic confusion, an epithelioid cell-predominant variant of renal angiomyolipoma has recently been described. HMB-45 immunoreactivity correlates with ultrastructural striated organelles that closely resemble premelanosomes, although no evidence of melanogenesis has been documented in this tumor. OBJECTIVE: To further characterize the immunophenotypic and ultrastructural profile of renal angiomyolipoma based on phenotypic cell type (epithelioid, spindle, and adipocytic cell). DESIGN: Formalin-fixed, paraffin-embedded tissues from 27 renal angiomyolipomas and 8 renal cell carcinomas were immunostained with monoclonal antibodies to the melanoma-associated antigens HMB-45, HMB-50, NKI/C3 (CD63), and tyrosinase; the smooth muscle-related antigens calponin and muscle-specific actin (HHF-35); S100; and cytokeratin (CK). All renal angiomyolipomas were also immunostained with a polyclonal antibody to renin. Ultrastructural examination was performed on 9 selected cases. RESULTS: All renal angiomyolipomas stained positive for HMB-45, HMB-50, NKI/C3, muscle-specific actin (HHF-35), and calponin. Overall, HMB-45, HMB-50, and NKI/C3 preferentially stained the epithelioid cells. Tyrosinase staining was present in 50% of the renal angiomyolipomas with adequate tissue for staining (12 of 24 cases); positive staining and intensity paralleled HMB-45, HMB-50, and NKI/C3. Muscle-specific actin (HHF-35) and calponin preferentially stained the spindle cells. The adipocytic cells stained positive for both melanoma-associated antigens and smooth muscle antigens. Epithelioid cells, spindle cells, and adipocytic cells were CK, S100, and renin negative. Ultrastructural findings paralleled immunohistochemical staining patterns. Premelanosome-like organelles and electron dense granules were more readily detected in the epithelioid cells within the tumor, whereas ultrastructural characteristics of smooth muscle cells were more easily found in the spindle cells. All renal cell carcinomas stained positive for CK, NKI/C3 staining was variable, and all were negative for HMB-45, HMB-50, smooth muscle actin (HHF-35), and calponin. CONCLUSION: In renal angiomyolipoma, the epithelioid and spindle cells have preferential staining patterns for melanoma-associated antigens versus smooth muscle antigens, respectively. Positivity in renal angiomyolipoma for HMB-50, NKI/C3, and tyrosinase, in addition to HMB-45, provides evidence for the presence of different melanoma-associated gene products. Immunophenotypic overlap of the 3 histologically distinct renal angiomyolipoma cell populations suggests a common cell line, supporting a unitarian concept for renal angiomyolipoma. Ultrastructural characteristics of the 3 renal angiomyolipoma cell phenotypes parallel the immunophenotype, giving further support to a common cell line. Our study lends further credence to the perivascular epithelioid cell concept as proposed by Bonetti and colleagues.     

Angiomyolipoma mimicking true lipoma of the liver: report of two cases

Hepatic angiomyolipoma (AML) is very rare and only about 80 cases have been reported. The tumor is fundamentally heterogeneously composed of the three tissue components of blood vessels, smooth muscle cells (SMC), and fat cells. Two cases of hepatic AML are reported here, both of which are histologically composed predominantly of a fat cell element and resembled true lipoma (lipomatous AML). However, careful examination of both tumors revealed the presence of a small amount of epithelioid SMC, especially around blood vessels. Immunohistochemical study using monoclonal antibody for melanoma (HMB-45) clearly revealed a small amount of HMB-45-positive SMC around the blood vessels and scattered in the diffuse fat cell growth in both tumors. Since no liver tissue components or primary liver tumors are reactive with HMB-45 except AML cells, the presence of HMB-45-positive cells within the tumor clearly established the diagnosis of hepatic AML. Any fatty tumor or focal fatty lesion of the liver that superficially resemble true lipomas should be tested for the presence of HMB-45-positive SMC in the tumor to differentiate it from AML.     

Malignant angiomyolipoma in the liver: a case report with pathological and molecular analysis

Malignant angiomyolipoma (AML) of the liver is rare. We report a case of AML with malignant transformation and metastases. A 30-year-old man had developed giant hepatic masses. Microscopically, the periphery of the tumor showed components of classic hepatic AML, but the central region contained atypical epithelioid components with extremely pleomorphic and hyperchromatic nuclei with frequent mitotic figures. Immunohistochemical analysis revealed that the epithelioid cells were positive for HMB-45 and smooth muscle actin. Furthermore, the atypical epithelioid cells displayed P53 immunoreactivity and mutation at exon 7 for p53. The tumor showed a typical monoclonal pattern but no loss of heterozygosity or microsatellite instability. Markedly atypical epithelioid cells with vascular invasion, distant metastasis, and fatal outcome were interpreted as malignant characteristics of hepatic AML. It is suggested that large tumor size, pleomorphic nuclei with high proliferation activity, and P53 immunoreactivity may predict the existence of malignant transformation of hepatic AML.     

Retroperitoneal lipomatous angiomyolipoma associated with amyloid deposition masquerading as well-differentiated liposarcoma

Reported herein is a case of retroperitoneal angiomyolipoma associated with amyloid deposition, masquerading as well-differentiated liposarcoma. A 16 x 13 cm lipomatous tumor was resected from the perirenal retroperitoneum of a 71-year-old woman. Microscopically, the tumor was exclusively composed of mature adipose tissue and abnormal thick blood vessels, but bundles of smooth muscle were lacking. In addition, amyloid was deposited between fat cells. Initially, well-differentiated liposarcoma was highly suspected. However, there were a few epithelioid cells with clear vacuolated cytoplasm within the vessel walls, which were immunoreactive for smooth muscle markers and HMB-45. Real-time polymerase chain reaction failed to demonstrate the amplification of the murine double-minute type 2 gene and cyclin-dependent kinase 4 gene in this tumor. Therefore, the tumor was diagnosed as lipomatous angiomyolipoma. After the diagnosis, it was found that the patient had multiple myeloma and cardiac amyloidosis, suggesting that the amyloid deposition within the tumor was a complication of the myeloma. Lipomatous angiomyolipoma may be a diagnostic pitfall of retroperitoneal lipomatous tumors.     

Hepatic angiomyolipomas with a deceptive trabecular pattern and HMB-45 reactivity

We report two cases of giant hepatic angiomyolipoma with a prominent component of epithelioid smooth muscle cells exhibiting a distinctive trabecular arrangement. These cells possessed peripherally vacuolated and centrally condensed hyaline cytoplasm. The nuclei were eccentrically placed in the cytoplasm. Immunohistochemically, they expressed HMB-45 intensely in the central condensed cytoplasm and actin in a perimembranous fashion. Staining for desmin, myoglobin and vimentin was negative. HMB-45 may prove to be a sensitive marker for angiomyolipoma with epithelioid cells. Hepatocellular carcinoma and other hepatic tumours with polygonal clear cells can be readily distinguished by these means.     

Hepatic angiomyolipoma: report of two cases with emphasis on smear cytomorphology and the use of cell block with immunohistochemical stains

Angiomyolipoma is a benign mesenchymal lesion that occurs most commonly in the kidney. Its occurrence in the liver is relatively rare. We report two cases of hepatic angiomyolipoma diagnosed by ultrasound-guided, needle aspiration biopsy. One of the patients was a previously healthy 62-yr-old woman who presented with a hepatic mass incidentally during a healthy examination. The other patient was a 67-yr-old man, a victim of chronic hepatitis C, who was found to have a hepatic tumor in the right lobe during regular follow-up. Cytologic preparations of the two hepatic masses showed some mature adipocytes admixed with clusters of variable-sized mesenchyme-like cells with fibrillar cytoplasm and indistinct cytoplasmic borders. Some of the cells were round to oval and others were spindle shaped with oval, cigar-shaped or elongated nuclei. The nuclear chromatin was fine and some cells showed round nucleoli. No thick-walled blood vessels were noted in the cytological smears. In the cell block preparations, a mixture of thick-walled blood vessels, mature adipose tissue, and bundles of variable-sized smooth muscle cells were noted. The spindle or epithelioid smooth muscle cells were positive for vimentin, alpha-smooth muscle actin, and human melanoma black (HMB)-45 but negative for desmin and S100 protein in immunohistochemical stains. The purpose of the current study is to describe cytological features of this lesion with differential diagnosis because pathologists may be called on to render a diagnosis on needle aspiration. HMB-45 has been proved to be a sensitive marker for the smooth muscle component of angiomyolipoma. Cell block preparations assisted with immunohistochemical staining should be emphasized for definite diagnosis. Although a surgical procedure may still be necessary once a diagnosis of angiomyolipoma is made, treatment may be tailored for a less aggressive procedure than for malignant hepatic nodules.     

Extrarenal retroperitoneal angiomyolipoma: description of a case and review of the literature

A case of retroperitoneal extrarenal angiomyolipoma is described. The patient, a 61-year-old woman, presented with a large retroperitoneal lipomatous mass. Histologically, it consisted of lipomatous tissue. Focally, there was interstitial and perivascular proliferation of bland oval and epithelioid cells with a large, eosinophilic or clear cytoplasm. Immunohistochemically, these elements were positive for smooth muscle actin and HMB-45. The literature on retroperitoneal extrarenal angiomyolipoma is briefly reviewed. It is important that the pathologist recognize this lesion, even when it is located in the retroperitoneum outside the kidney, and differentiate it from a liposarcoma.     

Monotypic epithelioid angiomyolipoma of the liver

AIMS: Monotypic epithelioid angiomyolipoma is a recently recognized renal tumour, which is composed purely of epithelioid cells coexpressing markers of both smooth muscle differentiation and melanogenesis (HMB45). We report here the first case of monotypic epithelioid angiomyolipoma arising in the liver. CASE DETAILS: A 30-year-old woman without tuberous sclerosis complex (TSC) was incidentally found to have a hepatic mass by ultrasonography. Grossly, the resected tumour showed a nodule-in-nodule appearance, with large areas of haemorrhagic necrosis. Microscopically, the tumour was composed of pleomorphic epithelioid cells with clear, eosinophilic cytoplasm. Neither adipocytes nor abnormal vessels were recognized in the tumour. Immunohistochemically, the tumour cells were strongly positive for HMB45 and S100 protein, focally positive for desmin, vimentin and smooth muscle actin, and negative for epithelial markers (cytokeratins, EMA). Ultrastructural analysis showed numerous dense granules with some striated ones resembling melanosomes, myofilaments and pinocytic vesicles in the cytoplasm. Molecular analysis showed no allelic loss of the TSC2 region or 12 other chromosomal regions. The patient is free of disease over 1 year after the operation. CONCLUSION: We consider that this hepatic tumour is closely related to angiomyolipoma, and a counterpart of renal monotypic epithelioid angiomyolipoma.     

肝脏血管平滑肌脂肪瘤9例临床病理分析

目的探讨肝脏血管平滑肌脂肪瘤(hepatic angiomyolipoma,HAML)的临床病理特点、诊断及鉴别诊断。方法对9例HAML进行临床病理学观察与免疫组化标记及复习有关文献。结果 9例HAML年龄28～56岁,平均44.2岁,均无结节硬化症。术前影像诊断多数为肝癌。眼观:肿瘤直径1.2～14 cm。肝左叶4例、肝尾状叶3例和肝右叶2例。肿瘤境界清楚,无包膜,质地脆、易碎,可见出血、坏死。镜检:瘤组织由上皮样细胞、平滑肌样细胞、脂肪组织和厚壁血管组成。上皮样细胞体积大或巨大,呈多边形,胞质丰富,嗜酸性或空泡状,核仁明显,可见核内包涵体,偶见多核巨细胞。平滑肌样细胞呈梭形,9例中有4例几乎缺如脂肪组织。瘤细胞弥漫性或巢团状排列。瘤组织出血、坏死明显,呈浸润性边缘。免疫组化标记:瘤细胞HMB-45及Melan-A阳性,SMA和vimentin散在阳性,CK、EMA、AFP均阴性。结论 HAML是一种罕见的间叶组织源性肿瘤,多见于女性,组织学上以单一方向分化的大上皮样细胞为主,瘤细胞较为特异的表达HMB-45及Melan-A。免疫组化标记可与其它肝脏肿瘤鉴别。     

Angiomyolipoma of the bladder

Angiomyolipoma of the bladder is an extremely rare neoplasm. We report a case of a 55-year-old woman with an angiomyolipoma of the bladder visualized on pelvic sonogram as a 5 mm polyp in the floor of the bladder. The lesional tissue consisted of spindle cells, epithelioid cells, and adipocytes, with occasional thick-walled blood vessels. Immunohistochemical studies showed the spindle and epithelioid cells to be focally positive for HMB-45 and diffusely positive for actin and muscle cell antigen (HHF-35), which confirmed the diagnosis of angiomyolipoma. A review of the recent literature on the pathogenesis of angiomyolipoma follows.     

Lymphangiomyomatosis and angiomyolipoma: closely related entities characterized by hamartomatous proliferation of HMB-45-positive smooth muscle

Angiomyolipoma is a hamartomatous condition which can occur as a component of the tuberous sclerosis complex. Lymphangiomyomatosis, another hamartomatous lesion occurring predominantly in the lungs, has long been suspected to be related to angiomyolipoma and tuberous sclerosis because of occasional clinical associations. We undertook this study to provide further support for the close relationship between these two entities. Five cases of lymphangiomyomatosis and 20 case of angiomyolipoma were retrieved for histological review and immunohistochemical studies. The antibodies used were anti-muscle specific actin (HHF-35), anti-desmin (D33) and antimelanoma (HMB-45). Lesions featuring smooth muscle proliferation were used as controls. The proliferated smooth muscle cells in both lymphangiomyomatosis and angiomyolipoma were much plumper and paler or even clear, when compared with the deeply eosinophilic cytoplasm of the normal spindly smooth muscle cells and those of leiomyomas. Their nuclei were round to oval and pale rather than elongated and dark. Cells with bizarre nuclei were commoner in angiomyolipoma (18/20 cases) than lymphangiomyomatosis (1/5). In 12 cases of angiomyolipoma there were foci indistinguishable from lymphangiomyomatosis, i.e. plump spindle cells arranged in short fascicles around ramifying endothelium-lined spaces. All five cases of lymphangiomyomatosis stained for muscle-specific actin, desmin and HMB-45. For angiomyolipomas, the positivity rates for these markers were: 20/20, 17/20 and 18/20, respectively, including one case that was negative for both desmin and HMB-45. The various smooth muscle proliferations and tumours selected as controls were uniformly HMB-45 negative. The distinctive cytological features, morphological overlap and immunophenotypic profile all support a close relationship between lymphangiomyomatosis and angiomyolipoma, which probably represent different morphological manifestations of hamartomatous proliferation of a peculiar form of HMB-45-positive smooth muscle.     

Angiomyolipoma of the large intestine: report of a case.

A case of an angiomyolipoma of the large intestine occurring in a 55-year-old man without evidence of tuberous sclerosis is reported. Endoscopically, the lesion resembled a sessile adenomatous polyp. The tumor measured 1 cm. Histologic examination revealed a lesion composed predominantly of spindle and epithelioid cells with significant nuclear atypia. Mitoses were rare. The tumor was strongly positive for HMB-45, CD68, vimentin, desmin, and smooth muscle actin. Rare scattered cells reacted with CD34. No residual tumor was found in the resected colon.     

Clinicopathologic features of renal epithelioid angiomyolipoma: report of one case and review of literatures

Epithelioid angiomyolipoma (EAML) is a rare renal mesenchymal tumor with malignant potential and is frequently associated with tuberous sclerosis complex (TSC). As metastasis of the tumor cells occur early, EAML is considered a potentially malignant tumor type and intrigues further research on it. Under the microscope, we could find the tumor was composed of atypical polygonal cells sheet mixed with classic angiomyolipoma (AML) components such as blood vessels with notable thick vascular walls, smooth muscle-like cells and adipocytes. Immunohistochemical studies showed that epithelioid cells were focally positive for vimentin, melanocytic markers (HMB-45), myoid markers (α-smooth muscle actin), CD34 and CD68; negative for cytokeratin, epithelial membrane antigen, CD10, and S-100. And the Ki67 index showed approximately 3%. Here, we report the morphological and immunohistochemical features of clinically or histologically malignant renal EAML and discuss its diagnosis, differential diagnosis and the prognosis.     

Hepatic angiomyolipoma resembling an inflammatory pseudotumor of the liver. A case report

Hepatic angiomyolipoma (AML) may demonstrate a marked histologic diversity and is frequently misdiagnosed. HMB45 is a promising marker for this tumor and is expected to facilitate the recognition of some AMLs with unusual morphology. We report on a case of hepatic AML exhibiting histologic features that were similar to inflammatory pseudotumor (IPT) or to IPT-like follicular dendritic cell (FDC) tumor of the liver. The patient was a 21-year-old Japanese woman with a mass in the left lobe of the liver (70 x 73 mm). There were no clinical features of tuberous sclerosis. Histologically, numerous inflammatory cells, including small lymphocytes, plasma cells, and histiocytes, showed diffuse infiltration throughout the lesion. However, the present case also shared some of the morphologic findings of hepatic AML, including clusters of smooth muscle cells with clear cytoplasm, a few scattered adipose cells, and thick-walled blood vessels. Moreover, the smooth muscle cells consisted of spindle-shaped cells or larger, more rounded cells with either clear cytoplasm or eosinophilic epithelioid cell features positive for vimentin, muscle-specific actin, and smooth muscle actin. HMB45 immunostaining confirmed the diagnosis of AML. The present case indicates that IPT or IPT-like FDC tumor should be added to the list of differential diagnoses for AML of the liver.     

Angiomyolipoma of the anterior mediastinum

Angiomyolipoma is a benign tumor composed of varying proportions of smooth muscle cells, blood vessels, and adipose tissue that most commonly occurs in the kidney. Sporadic lesions and lesions arising in the setting of the tuberous sclerosis complex have been reported in extrarenal sites. We present the case of an incidentally discovered angiomyolipoma in the anterior mediastinum. Thymoma was suspected clinically, and the lesion was composed mainly of spindled-to-epithelioid cells arranged in a histologic pattern reminiscent of hemangiopericytoma, a pattern that has been described in thymoma. Immunohistochemical stains revealed positivity for smooth muscle actin and HMB-45, revealing the expression of smooth muscle and melanocytic markers characteristic of angiomyolipoma and other lesions in the PEComa family.     

Perivascular epithelioid cell tumor (PEComa) of the liver: a case report and review of the literature

Perivascular epithelioid cell tumor (PEComa) is rare entity and has been described only recently. By immunohistochemistry and genetics it belongs to the family of tumours which comprises angiomyolipoma, clear cell "sugar" tumor of lung, lymphangioleiomyomatosis and clear cell myomelanotic tumor of ligamentum falciforme/teres hepatis. We describe an unusual case of hepatic PEComa arising in a 55-year-old woman with previous history of glioblastoma. Histologically the tumor grew in expansive way, and was composed of clear and eosinophilic epithelioid cels, without vascular or lipomatous component characteristic of angiomyolipoma. There was mild nuclear pleomorphism, sporadic mitotic activity and haemorrhage without necrosis. On immunohistochemistry, the tumor was HMB-45+50, Melan-A and smooth muscle actin positive. Tyrosinase, S-100 protein, cytokeratin coctail, EMA, vimentin, muscle specific actin, CD10, TTF-1, hepatocyte, desmin and cyclin D1 were negative. Sporadic nuclear p53 positivity was seen. The main differential diagnosis of hepatic PEComa includes clear cell variant of liver cell adenoma and hepatocellular carcinoma, metastases of various clear cell carcinomas and metastasis of malignant melanoma. In respect of uncertain biologic potential of PEComa, long term follow up is indicated.     

Immunohistochemical study of hepatic angiomyolipoma

An immunohistochemical study was performed on nine hepatic angiomyolipomas (AML) found in eight patients. Histologically, the tumors were fundamentally composed of the three heterogeneous tissue components of blood vessels, smooth muscle cells (SMC), and fat cells, although the proportions and distributions were quite variable from tumor to tumor and from area to area in the same tumor. Additionally, cellular pleomorphism and atypia with occasional bizarre giant cells were found in the SMC component. This histologic feature might lead to a mistaken diagnosis of malignant neoplasm, and pathologists should therefore be aware of the broad histologic spectrum of hepatic AML. However, the immunostaining patterns were basically the same in all nine tumors. All tumor components were negative for epithelial membrane antigen (EMA) and for cytokeratin. The spindle-shaped SMC component of the tumor was occasionally positive for vimentin, desmin and alpha-smooth muscle actin, whereas epithelioid SMC were negative for all three. Both the epithelioid and spindle-shaped SMC were occasionally positive for S-100 and neuron-specific enolase. All types of SMC in the tumor, whether spindle, epithelioid, intermediate or pleomorphic SMC, were strongly positive for HMB-45, a melanoma-specific monoclonal antibody. Fat cells were occasionally positive for S-100. Endothelial cells were positive for factor VIII-associated antigen. Among hepatic tumors HMB-45 reactivity is, so far as we know, found exclusively in the SMC of AML, and the HMB-45 reactivity of a hepatic tumor is thus clearly an important piece of information in the diagnosis of AML.     

Renal epithelioid angiomyolipoma--a close mimic of renal cell carcinoma. Report of a case and review of the literature

The epithelioid variant of angiomyolipoma (EAML) is a rare tumor of unpredictable behavior that is composed of epithelioid, spindle, and giant cells and contains no or only a minimal amount of lipomatous tissue. The picture can lead to an erroneous diagnosis of renal cell carcinoma or sarcoma. We report on a case of EAML in the kidney of a 47-year-old female without any signs of tuberous sclerosis and review the literature. Grossly, a well-demarcated, spheroid, largely hemorrhagic tumor measuring 4.2 cm in diameter occupied the central third of the kidney. Histologically, it was solid, highly cellular, with occasional microcysts, composed of medium to large epithelioid cells with clear or oxyphilic cytoplasm, short spindle cells, and numerous giant multinucleated cells. After extensive sampling, adult-appearing fat tissue was found to present as rare foci of microscopic dimensions. Immunohistochemically, the tumor cells showed positive reactions with antibodies against HMB-45, melan A, CD-68, muscle-specific actin, and, rarely, smooth muscle actin. Cytokeratins and epithelial membrane antigen were negative. The EAML is a variant growing in a carcinoma-like pattern that can lead to an erroneous diagnosis of renal cell carcinoma. An extensive sampling and HMB-45 and CD-68 positivity combined with cytokeratin negativity are of paramount importance for the correct diagnosis. As a sporadic renal tumor it followed a benign course in most of the reported cases.