Renal angiomyolipoma with sarcomatous transformation and pulmonary metastases

Association of cystic nephroma with angiomyolipoma in the same kidney

The synchronous occurrence of two different renal tumors in a patient is a rare event. Here we report an incidentally discovered coexistence of cystic nephroma with angiomyolipoma in the right kidney. The patient was a 68-year-old woman without the tuberous sclerosis complex. To the best of our knowledge, this combination of neoplasms has not yet been described before. This rare situation emphasizes the need for careful diagnosis and the correct management of coincident renal neoplasms.

Malignant epithelioid angiomyolipoma ('sarcoma ex angiomyolipoma') of the kidney: a case report and review of the literature

Malignant epithelioid angiomyolipoma is a recently described rare tumor of the kidney. Its existence has been questioned, however, on the basis of incomplete evidence of malignant behavior, the absence of an associated classic angiomyolipoma component, or the absence of immunoreactivity for HMB-45 in some cases. We describe a case that was HMB-45-positive and arose in association with a classic angiomyolipoma. The patient was treated with a partial nephrectomy. Three years later, she developed rapidly enlarging liver nodules. A fine-needle aspiration of the liver confirmed the presence of pleomorphic epithelioid cells morphologically and immunohistochemically identical to those comprising the primary renal tumor. After two cycles of treatment with doxorubicin, there was a 50% reduction in the size of the tumors with marked improvement in performance status. We believe this case confirms the existence of a malignant epithelioid angiomyolipoma.

Retroperitoneal epithelioid angiomyolipoma leading to fatal outcome

Epithelioid angiomyolipoma (AML) is a newly established variant of AML, characterized by monomorphous epithelioid cells that show HMB-45 immunopositivity, and it often displays aggressive behavior. To date, they have mostly appeared in the kidneys; however, the present autopsy case of a 43-year-old female without the stigmata of tuberous sclerosis complex had a huge retroperitoneal mass, accompanied by involvement of the regional lymph nodes. Histopathologically, the tumor was composed of round, polygonal or short spindle-shaped monomorphous cells with abundant eosinophilic cytoplasm and large nuclei with frequent multinucleation. Mitotic figures were scattered. Mature fat cells and thick-walled abnormal blood vessels were totally absent. Immunohistochemically, the tumor cells were reactive with HMB-45 and alpha-smooth muscle actin antibodies. In spite of curative surgery and repeated radio- and chemotherapy, the tumor continued to grow and brought about the patient's death 4 years after the initial symptoms. At autopsy, the peritoneal cavity was filled with the tumor mass exceeding 5.5 kg. Histopathological features were essentially the same as those of biopsy samples, but the cellular pleomorphism and emperipolesis were more easily identified. This report calls attention to this unusual manifestation of AML in the retroperitoneum and the importance of distinguishing it from sarcomas and/or paragangliomas.

Renal angiomyolipoma with epithelioid sarcomatous transformation and metastases: demonstration of the same genetic defects in the primary and metastatic lesions

Angiomyolipoma (AML) is a benign neoplasm that occurs either sporadically or in patients with tuberous sclerosis complex (TSC) and shows frequent allelic losses at chromosome arm 16p. It has been suggested recently that the melanogenesis marker-positive perivascular epithelioid cell (PEC) has been found consistently in AML. The authors report a 50-year-old woman without evidence of TSC affected by classic renal AML containing an area composed of atypical epithelioid cells with the same morphoimmunophenotypic characters of PEC. After 7 years from surgical removal of the lesion, the patient developed a local recurrence and successive lung and abdominal metastases that showed morphologic and immunohistochemical features overlapping those of the epithelioid area of the previously removed AML. Genetic analysis showed that the classic AML and its epithelioid area as well as the pulmonary and abdominal metastases shared the same allelic loss on chromosome arm 16p. Based on these findings, the authors view this case as evidence of a malignant transformation of a classic AML with morphologic, immunophenotypic, and genetic demonstration of its clonal origin.

Malignant angiomyolipoma of the liver: a hitherto unreported variant

AIMS

After their original recognition in the kidney, angiomyolipomas (AMLs) have been reported in the liver for more than 20 years. In the kidney, five cases of malignant AML have been reported. We report the first case of malignant hepatic AML.

METHODS AND RESULTS

A 70-year-old female patient presented with abdominal discomfort. Clinical examination revealed a palpable liver. CT scan showed a polymorphous hypervascular lesion in the right liver lobe. A biopsy was taken and resulted initially in a differential diagnosis between a hepatocellular carcinoma, a metastatic tumour (possibly of renal origin) and angiomyolipoma (AML). After immunohistochemistry, a hepatic AML was suggested, given the immunoreactivity for HMB45/NKIC-3. The mass was resected 5 years later because of relapsing abscess formation. Gross examination of the resection specimen showed a focally encapsulated brown mass with focal necrosis. Microscopic examination showed a tumour growing in sheets, separated by sinusoidal-like vessels. Most of the tumour cells had a large, polygonal, clear cytoplasm, often with eosinophilic condensation around the nucleus. There was prominent vascular invasion. Immunohistochemistry (reactivity for HMB-45, NKIC-3, S100 and alpha smooth muscle actin, negativity for cytokeratin and vimentin) and electron microscopy confirmed the diagnosis of monomorphic epithelioid AML with prominent vascular invasion. Seven months after tumour resection, the patient died of recurrent disease.

CONCLUSIONS

This case highlights the importance of immunohistochemistry and electron microscopy in diagnosing this type of tumour. Possibly, in the past, malignant AML of the liver has been misdiagnosed as HCC.

Paratesticular liposarcoma with smooth muscle differentiation mimicking angiomyolipoma

AIMS

To discuss the differential diagnosis of a case of well-differentiated liposarcoma which had areas resembling angiomyolipoma-a feature which, to our knowledge, has not been reported previously.

METHODS AND RESULTS

A tumour in the paratesticular region had apparently been present for 40 years, but had grown recently. A fat component containing lipoblasts was admixed with areas resembling angiomyolipoma, i.e. desmin positive, but HMB45-negative smooth muscle proliferation with atypia and thick-walled blood vessels devoid of elastin.

CONCLUSION

The diagnosis of liposarcoma, rather than angiomyolipoma with adipose atypia, in this case is based on the fact that smooth muscle differentiation is documented in liposarcoma, lack of HMB45 staining and recent clonality studies which suggest that the fat in angiomyolipoma is not neoplastic.

Giant abdominopelvic epithelioid angiomyolipoma associated with tuberous sclerosis: report of a case

Tuberous sclerosis is a hereditary autosomal-dominant disease characterized by hamartomas that can develop in any organ. We report herein the case of a 34-year-old female with tuberous sclerosis and a huge abdominopelvic mass that started growing quickly 2 years after its diagnosis. The patient had undergone several previous operations for hydrocephalus and cerebral tubers, and a nephrectomy for right renal angiomyolipoma. On admission, she was in poor general health with renal failure, severe anemia, and weight loss. A laparotomy revealed that the tumor occupied the pelvis, the lower and part of the upper abdomen, and was hypervascularized, with an extremely irregular surface covered in nodules, vegetations, and areas of hemorrhagic necrosis. The development of the mass and the impossibility of recognizing the internal genital organs led us to assume that the formation had originated from these. Frozen-section examination indicated an undifferentiated tumor that had not been completely resected. Her postoperative course was complicated by bronchopneumonia and progressive renal failure. The patient died 10 days after surgery due to cardiorespiratory failure. A histological diagnosis of epithelioid angiomyolipoma was confirmed. Although it is presently impossible to determine whether angiomyolipoma with predominant epithelioid cells is more aggressive than typical angiomyolipoma, it definitively demonstrated local aggressive behavior in this patient.

Renal angiomyolipoma: a clinicopathologic, immunohistochemical, and follow-up study of 46 cases

We reviewed 46 cases of renal angiomyolipoma covering the period from 1977 to 1997. Eight cases were associated with tuberous sclerosis and one with lymphangiomyomatosis. Histologically, the lesions were most often classic with the three usual components, i.e., mature adipose tissue, thick-walled blood vessels, and smooth muscle. Seven cases were particularly misleading: three cases were entirely adipose mimicking liposarcoma: two cases had an exclusively smooth-muscle component, one mimicking lymphangiomyomatosis and one with epithelioid cells; another case had a monophasic epithelioid pleomorphic component ("REON": renal epithelioid oxyphilic neoplasm) and proved to be fatal; and another case was associated with collecting duct carcinoma. The immunohistochemical profile showed the coexpression of alpha-smooth-muscle actin and HMB45. Our study is the first to show positivity of estrogen and progesteron receptors or both in more than 25% of cases. Of 35 cases with follow-up information, only one patient died of malignant spread of angiomyolipoma.

Cytologic analysis of renal angiomyolipoma: a comparison of radiologically classic and challenging cases

BACKGROUND

Angiomyolipoma is a benign kidney tumor with distinctive pathologic and clinical features. Because the prognosis differs from many other renal and retroperitoneal tumors, accurate diagnosis on cytologic material may be important for appropriate management.

METHODS

A retrospective analysis of cytologic material from eight patients with histologically confirmed angiomyolipomas was performed. The findings are described.

RESULTS

Three cases were diagnosed radiologically as angiomyolipoma, three were diagnosed as renal cell carcinoma, one was diagnosed as a "renal mass," and one was diagnosed as a fat-containing adrenal tumor. Compared with the tumors that were suggestive radiologically of angiomyolipoma, tumors that were suspicious radiologically for renal cell carcinoma tended to contain less fat on cytologic examination. One fat-containing tumor was not diagnosed as angiomyolipoma because the tumor was believed to be adrenal in origin. Cytologically, cohesive stromal fragments were comprised of cells ranging from epithelioid to elongate. Stromal atypia was present in 7 of 8 cases (88%) but was marked in only 2 cases (25%). Thick-walled vessels were noted in 3 of 8 cases (38%).

CONCLUSIONS

The cytologic diagnosis of angiomyolipoma is difficult in cases in which the radiologic diagnosis is not clear. The liberal use of immunostains is advised in the evaluation of stromal renal tumors.

Angiomyolipoma of the parotid gland: a case report

Angiomyolipoma is a hamartomatous process that most frequently occurs as a single lesion or multiple foci in the kidneys of patients affected by tuberous sclerosis. Angiomyolipoma can also arise in extrarenal sites, among which the liver is the most frequently recorded. Only rare cases of angiomyolipoma located in the head and neck region (ear and oral and nasal cavity) have been described. The purpose of the present article is to report a case of angiomyolipoma of the parotid gland. A 68-year-old woman appeared for treatment with a slow-growing nodule located in her right parotid gland. Ultrasound examination revealed a heterogeneous nodule with well-defined margins. The nodule was surgically removed by total parotidectomy and showed the characteristic appearance of angiomyolipoma, with an admixture of fat smooth muscle cells, and tortuous, thick-walled blood vessels. Careful physical examination of the patient failed to reveal features of tuberous sclerosis. Angiomyolipoma should be considered in the differential diagnosis of mesenchymal lesions involving the salivary gland.

Composite renal cell carcinoma and angiomyolipoma: a study of the histogenetic relationship of the two lesions

The purpose of the present study was to investigate the possible histogenetic relationship of renal cell carcinoma (RCC) and angiomyolipoma (AMYL) occurring in the same renal nodule by examining two cases of composite RCC and AMYL in patients without stigmata of tuberous sclerosis and by reviewing the medical literature of similar cases. Case 1 represents an epithelioid variant of AMYL with multiple additional nodules of typical AMYL in a surgically removed kidney. The patient subsequently developed a lesion consisting of a mixture of epithelioid variant of AMYL and RCC 24 months later in the retroperitoneum and, an additional 4 months later, in the liver. The RCC cells resembled mononucleated epithelioid cells of the epithelioid AMYL except that they were focally reactive with epithelial membrane antigen (EMA) in the retroperitoneum and focally reactive with both EMA and cytokeratin (CK) in the liver. Case 2 consisted of a typical AMYL admixed with a chromophil cell RCC. A review of the medical literature revealed seven additional cases with histopathological findings similar to this case. All cases had multiple foci of typical AMYL. Immunostaining results are available in five tumors. Chromophil RCC showed variable reactivity with CK and EMA. In addition, RCC in the two cases in the present study also displayed a positive reaction with mucin staining and a positive reactivity with carcinoembryonic antigen. There appears to be a spectrum of histopathological and immunohistochemical changes from the epithelioid variant of AMYL through a mixed epithelioid AMYL/RCC to chromophil RCC in three successive specimens in case 1. Moreover, the intimate admixture of AMYL and RCC and the similar expression of epithelial markers of RCC in the two cases in the present study, as well as other cases in the literature, suggest that some RCC develop from the same precursor cell as AMYL or from a component of AMYL.

Hepatic angiomyolipoma: a clinicopathologic study of 30 cases and delineation of unusual morphologic variants

Hepatic angiomyolipoma (AML) is frequently misdiagnosed. HMB-45 is a promising immunomarker for this tumor that leads to recognition of some AMLs with unusual morphology. The purpose of this collaborative study is to better define the morphologic variations of AML. Thirty AMLs were examined, including four biopsy specimens and two fine-needle aspirates. The diagnosis was confirmed by the presence of HMB-45-positive myoid cells. Almost half the cases were originally misdiagnosed as carcinomas or sarcomas. There was marked female predominance (25:5), and the mean age was 48.7 years (range 29-68). Three patients (10%) had evidence of tuberous sclerosis and all had renal AML. According to the line of differentiation and predominance of tissue components, the tumors was subcategorized into mixed, lipomatous (> or = 70% fat), myomatous (< or = 10% fat), and angiomatous type. The mixed type was the most common (11 resected cases), comprising sheets of epithelioid muscle cells admixed with islands of adipocytes, abnormal vessels, and frequently, hematopoietic cells. Six tumors (including three from biopsy specimens) were heavily fatty and showed predominantly adipocytes with epithelioid and short spindle myoid cells webbed between fat cells. Of 10 myomatous AMLs, five tumors showed a pure sinusoidal trabecular pattern and comprised mainly epithelioid cells. Typically, mature adipocytes were absent or scanty, but fat was seen as fine droplets within cytoplasm or as occasional large globules in sinusoids. Pelioid and inflammatory pseudotumor-like patterns were identified focally. Regarding cellular features of the myoid cells, most of the epithelioid cells were either eosinophilic or clear with spiderweb cell morphology. Three AMLs showed an almost purely oncocytic appearance with scanty fat. Large pleomorphic epithelioid cells existed as small foci. Spindle cells arranged in long fascicles were uncommon. D-PAS-positive globules were common around pelioid areas. Brown pigments with staining characteristics of hemosiderin and/or melanin were noted. In conclusion, we propose HMB-45-positive myoid cells as the defining criterion of hepatic AML, which is a tumor capable of dual myomatous and lipomatous differentiation and melanogenesis. Because of its protean morphologic appearance, recognition of the various variant patterns and cell types is important for a correct diagnosis, assisted by immunohistochemical confirmation with HMB-45. Trabecular and oncocytic cell tumors appear to stand out as distinctive subtypes.

Multiple giant angiomyolipomas with a polygonal epithelioid cell component in tuberous sclerosis: an autopsy case report

A recent case of angiomyolipoma (AML) with a prominent component of polygonal epithelioid cells is described. A 27-year-old Japanese male with tuberous sclerosis presented with massive abdominal tumors increasing progressively in size. The patient died of respiratory disturbance and the autopsy revealed massive tumors in the bilateral kidneys, liver and lymph nodes, subependymal giant cell glioma of the brain and lymphangiomyomatosis of the lungs. The giant tumors were an unusual type of AML with a component of polygonal epithelioid cells, which showed a hepatocellular carcinoma-like pattern in some areas. Smooth muscle components comprising spindle cells, short or plump spindle cells and polygonal epithelioid cells frequently exhibited positive staining for HMB-45 but negative staining for epithelial cell markers. The unusual AML presented in this case was thought to be of low-grade malignancy and slow growing. It has been suggested that angiomyolipomas with diffuse areas of epithelioid cell component are potentially malignant. Immunostainings positive for HMB-45 but negative for epithelial cell markers are considered to be useful in differentiating AML with polygonal epithelioid cell component from other tumors, especially from renal cell carcinoma and hepatocellular carcinoma.

Clonal analysis of renal sporadic angiomyolipomas

Renal angiomyolipomas are benign tumors composed of variable amounts of mature fat, smooth muscle, and thick-walled blood vessels. They occur either sporadically or in association with tuberous sclerosis. Such tumors are considered as hamartomas, but few data are available concerning their pathogenesis. Indeed, it is not known whether angiomyolipoma is a congenital malformation or a neoplastic process. To answer this question, we assessed the clonality of sporadic angiomyolipomas using molecular analysis. Seven women (mean age, 59 years) with renal angiomyolipomas were included. DNA of the tumor and the normal adjacent kidney was extracted from archival paraffin-embedded tissue. DNA methylation pattern at a polymorphic site on the HUMARA gene was studied by polymerase chain reaction (PCR) amplification after methylation-sensitive enzyme digestion. This procedure enables the differentiation between polyclonal and monoclonal lesions according to their X-chromosome inactivation pattern. Five of the seven women included were informative for the HUMARA gene. The mean size of the angiomyolipomas was 53 mm (range, 18 to 110). In one case, a tumor thrombus was observed in the inferior vena cava. Clonal analysis showed that all of the angiomyolipomas and the tumor thrombus studied were monoclonal. This study shows that sporadic angiomyolipomas are monoclonal lesions consistent with neoplastic disorders. This result strongly supports the hypothesis that angiomyolipomas arise from the clonal proliferation of an uncommited cell, which will further evolve toward different cell types.

Renal angiomyolipoma in children: diagnositc difficulty in 3 patients

PURPOSE

Because angiomyolipoma is less common in children than in adults, its diagnosis can be difficult. We present 3 cases of pediatric angiomyolipoma in which diagnostic problems resulted due to the presenting characteristics.

MATERIALS AND METHODS

We report on 3 children with unilateral renal angiomyolipoma. Computerized tomography (CT) and ultrasonography revealed 3 large renal masses, 20, 7 and 8 cm. in diameter, respectively. A correct diagnosis was not made preoperatively in any case by CT, ultrasound or fine needle biopsy. Wilms tumor was suspected in the first patient who received preoperative chemotherapy. Imaging was inconclusive in the other 2 cases.

RESULTS

All patients underwent surgical exploration and subsequent nephrectomy due to the large size of the tumor. At followup 33, 23 and 13 months postoperatively all children were well without signs of recurrence.

CONCLUSIONS

It has been reported that the demonstration of fat on renal ultrasound and CT can diagnose angiomyolipoma in 95% of the cases. Most radiologists rely solely on CT demonstration of lipid density in the renal mass to diagnose angiomyolipoma but the identification at imaging of lipid tissue may be difficult in small tumors. In our cases the fat content of the tumors was less than 10% despite the large size. This low fat content results in misdiagnosis, since fatty tissue is also present in other renal tumors, such as lipoma, liposarcoma, teratoma and Wilms tumors. We recommend conservative surgery when tumor size permits in pediatric patients with angiomyolipoma to avoid chemotherapy.

Low-grade spindle cell carcinoma of the kidney

The authors report a renal cell carcinoma composed largely of spindle cells of Fuhrman's nuclear grade II in which the bland appearance of the cells and low mitotic index were reminiscent of a benign or low-grade smooth muscle tumor. Keratin immunostaining was positive, but evidence of epithelial differentiation was obtained by electron microscopy. The tumor was an incidental finding and it did not invade the perirenal fat or the renal vein. Follow-up is only 24 months but the histological features suggest that the prognosis may be better than that of a classic sarcomatoid renal cell carcinoma.

Epithelioid angiomyolipoma of the kidney: a report of five cases with a prominent and diagnostically confusing epithelioid smooth muscle component

We report five angiomyolipomas with a prominent component of epithelioid smooth muscle cells that occurred in patients from 20 to 48 (mean, 36) years of age. The tumors often posed problems in diagnosis, particularly with regard to distinction from renal cell carcinoma. Two patients had tuberous sclerosis. Two patients with more than 5 years' follow-up are alive and well. The epithelioid smooth muscle cells typically formed sheets that in two tumors were traversed by hyaline cords. The epithelioid cells ranged from medium sized and polygonal with slightly pleomorphic nuclei and eosinophilic cytoplasm to giant cells with prominent nucleoli. Hemorrhage, necrosis, and clusters of foamy macrophages were present in three tumors. Mitotic figures were easy to find in two of the tumors, but they were absent in the others. Obvious elements of typical angiomyolipoma were present in two tumors. The others contained only scattered, thick-walled blood vessels or a few fat cells suggestive of typical angiomyolipoma. None of the tumors was positive for low- or high-molecular-weight cytokeratins or epithelial membrane antigen. Actin was detected in the epithelioid areas in four tumors. Melanoma-associated antigens related to the gp100-cl gene product, HMB-45 and HMB-50, were present in all the tumors. Another melanoma-associated antigen, CD63 (NKI/C3), also was present in all the tumors, a finding suggesting that angiomyolipoma has features in common with melanoma beyond premelanosomal structures.

Multicentric renal angiomyolipoma associated with pulmonary lymphangioleiomyomatosis: case report, with histologic, immunohistochemical, and DNA content analyses

A 26-year-old pregnant woman presented with pulmonary lymphangioleiomyomatosis (LAM) and multicentric angiomyolipoma (AML) involving the left kidney and perirenal lymph nodes. In both tumors, smooth muscle cells were the predominant component. Immunohistochemically, these cells stained for vimentin, smooth muscle actin, desmin, and HMB-45. Estrogen receptors were weakly positive in LAM and negative in AML. Progesterone receptors were negative for both lesions. DNA content analysis studies showed the renal AML to be diploid with a minor aneuploid component, the lymph node AML aneuploid, and the LAM diploid. The diagnostic and prognostic significance of hormonal studies and DNA content analysis are discussed.

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 angiomyolipoma and pulmonary lymphangiomyomatosis: a non-fortuitous association]

Angiomyolipoma is a rare tumor, frequently associated with tuberous sclerosis, but not observed in its isolated form. Usually, patients with tuberous sclerosis presented with pathognomonic cutaneous and central nervous system lesions. But the thesis of "formes frustes" without typical stigmata was suggested. A case of bilateral and multifocal angiomyolipoma in a young woman without evidence of phacomatosis is reported. The association with a pulmonary lymphangiomatosis make us suspected "a forme fruste" of tuberous sclerosis.

Renal angiomyolipomas and HMB-45 reactivity

BACKGROUND

Renal angiomyolipomas (RAML) are mesenchymal hamartomas composed of varying amounts of blood vessels, smooth muscle, adipose tissue, and supporting connective tissue. Although most of these tumors are easy to recognize, some show unusual histologic features and may pose a diagnostic dilemma. Recent reports indicate that RAML are immunoreactive for HMB-45 antibody, which is directed against a premelanomasome-associated glycoprotein and is thought to be specific for melanocytic differentiation.

METHODS

To determine whether HMB-45 reactivity would differentiate RAML from other renal tumors, the authors immunostained 72 primary renal tumors, including 19 angiomyolipomas and 2 retroperitoneal liposarcomas extending into the kidney, with HMB-45 monoclonal antibody. Also, the immunohistochemical profile of 19 renal angiomyolipomas was investigated using a broad panel of immunostains, including cytokeratin (AE1/AE3), epithelial membrane antigen, vimentin, smooth muscle actin (SMA), desmin, muscle-specific actin (MSA), S-100 protein, and neuron-specific enolase (NSE).

RESULTS

All tumors except RAML were negative for HMB-45 antibody. HMB-45 immunoreactivity was present in 17 of 19 RAML. Seventeen of 19 were positive for SMA and MSA (HHF 35), 8 for desmin, 17 for vimentin, and 9 for NSE.

CONCLUSIONS

Based on this study, it was concluded that, along with SMA and MSA, HMB-45 reactivity is a useful tool to distinguish RAML, especially those with unusual morphological features, from other primary renal neoplasms, including liposarcomas that extend into the kidney.