Malignant pigmented clear cell epithelioid tumor of the kidney: clear cell ("sugar") tumor versus malignant melanoma

Malignant Pigmented Epithelioid Angiomyolipoma of the Kidney in a Child with Tuberous Sclerosis Complex

INTRODUCTION

Pigmented epithelioid angiomyolipoma is a variant of epithelioid angiomyolipoma (EAML) that has not previously been described in children with tuberous sclerosis.

CASE PRESENTATION

A 15-year-old boy with tuberous sclerosis had a rapidly enlarging renal mass associated with a left lung nodule. Microscopically it was a pigmented EAML, confirmed by immunohistochemistry.

DISCUSSION/CONCLUSION

The pigmented variant of EAML can arise and metastasize from the kidney of a teenager with tuberous sclerosis.

Perivascular epithelioid cell tumor (PEComa) of the cystic duct

Perivascular epithelioid cell tumors, also known as PEComas, are rare mesenchymal tumors composed mainly of epithelioid cells found in perivascular tissue. PEComas occur most frequently in the kidney, uterus, the gastrointestinal tract, liver, and retroperitoneum; those originating in the biliary tree are extremely rare. We report a case of benign PEComa of the cystic duct with positive TFE3 staining on immunohistochemistry.A 66-year-old woman was referred for a 20 mm mass adjacent to the common bile duct discovered incidentally on abdominal ultrasound. Laboratory data including tumor markers were unremarkable. The tumor appeared to arise from the cystic duct, showed early enhancement, and compressed the common bile duct on imaging studies. Endoscopic ultrasound-guided fine-needle aspiration revealed round- and spindle-shaped atypical cells with eosinophilic cytoplasm and brown deposits suggestive of melanin granules. Histological examination of the resected specimen revealed a tumor consisting of epithelioid cells forming an alveolar structure, with melanin pigmentation. Immunohistochemistry was positive for HMB-45 and TFE3, consistent with benign pigmented PEComa of the cystic duct. Melanotic, myogenic, and TFE3 staining are helpful when diagnosing PEComas arising in unusual locations.

Urological Melanoma: A Comprehensive Review of a Rare Subclass of Mucosal Melanoma with Emphasis on Differential Diagnosis and Therapeutic Approaches

Melanoma is reported as the 19th most common cancer worldwide, with estimated age-standardized incidence rates of 2.8-3.1 per 100,000. Although the origin is most frequently cutaneous, mucosal melanoma has been described several times in literature, and despite its rarity (only 1% of all melanomas), increasing attention is being paid to this disease form. Within this subgroup, melanomas of the uropoetic apparatus are a rarity among rarities. Indeed, less than 50 cases of primary melanoma originating from the urinary bladder have been described, and even less originating from the kidney, renal pelvis and urethra. In this work, we present a detailed review of the literature related to this subclass of mucosal melanoma, delve into the biological landscape of this neoplasm and discuss current approaches, future perspectives and potential therapeutic approaches.

Epithelioid Angiomyolipoma: A Case Report

Epithelioid angiomyolipoma is a recently recognized tumor entity. We report a case of epithelioid angiomyolipoma of the kidney that occurred in a 70-year-old female. The patient presented with massive abdominal hemorrhage and shock. There was no history of tuberous sclerosis complex. The tumor consisted of smooth muscle, adipocytes, small-to-medium-sized hyalinized blood vessels and numerous pleomorphic epithelioid cells with clear to eosinophilic cytoplasm. Mitosis was exceptional and no glandular pattern was recognizable. Immunohistochemically the epithelioid cells were strongly positive for HMB45 and CD68, focally positive for S-100, actin and vimentin, and negative for epithelial markers including epithelial membrane antigen and cytokeratins. Previous reports in the English literature suggest that epithelioid angiomyolipoma may have malignant potential. In our case, at six months from surgery the patient is alive and well without evidence of relapse or metastasis.

Pigmented perivascular epithelioid cell tumor (PEComa) arising from kidney: A case report

INTRODUCTION

Perivascular epithelioid cell tumor (PEComa) is a mesenchymal neoplasm composed of perivascular epithelioid cells with clear to eosinophilic cytoplasm. Pigmented PEComa arising from kidney is extraordinarily rare and sometimes can exhibit aggressive biological behavior.

CASE REPORT

We present here a rare case of pigmented renal PEComa in a 46-year-old female. The patient had complained of lumbago complicated with nausea and vomiting for 2 weeks and therefore was referred to our department. An enhanced computed scan revealed a 4 × 3 × 3 cm round-like mass in the lower pole of right kidney with inhomogeneous enhancement. The tumor cells immunestained was positive for HMB-45, focally positive for c-Kit (CD117), and negative for vimentin, S-100, AE1/AE3, CK-7, CK-18, CD-10, RCC antigen, CgA, DOG-1, EMA, smooth muscle actin, and synaptophysin. We successfully performed 3-dimensional laparoscopic resection of the neoplasm, which was then diagnosed as pigmented PEComa by postoperative pathology. No further growing lesion or metastasis was observed during a 1-year follow-up.

CONCLUSION

This case report shows that pigmented renal PEComa is often presented as a renal mass with nonspecific symptoms and imaging features. The gold diagnosis of renal pigmented PEComa is mainly based on the combination of histopathology and immunohistochemistry. Complete resection by 3-dimensional laparoscopic nephron-sparing surgery can be an effective therapeutic management.

Pancreatic perivascular epithelioid cell tumor: A case report with clinicopathological features and a literature review

Perivascular epithelioid cell tumor (PEComa) of the pancreas is an unusual tumor deriving from mesenchyma. This paper described a case of pancreatic PEComa, which was initially suspected as neuroendocrine carcinoma by biopsy, and therefore surgical treatment was recommended due to undetermined diagnosis. Examination of the surgical specimen under a microscope showed that the tumor cell’s morphology was epithelioid or spindle-shaped, and ranged in a nested pattern. Additionally, these cells had a large extent of acidophilic cytoplasm, no mitotic figures, and expressed HMB-45, melan-p, and smooth muscle actin immunohistochemically. Pathological examination indicated that PEComa originated from the pancreas, but symptoms related to tuberous sclerosis were absent. Since PEComa is extremely rare in the pancreas, it is likely to be ignored in differential diagnosis. In conclusion, our article highlighted the clinicopathological features of PEComa, and we conducted a literature review focusing on PEComa so as to deepen the understanding of this tumor type.

Xp11 neoplasm with melanocytic differentiation of the prostate harbouring the novel NONO-TFE3 gene fusion: report of a unique case expanding the gene fusion spectrum

Recently, an increasing number of TFE3 rearrangement-associated tumours have been reported, such as TFE3 rearrangement-associated perivascular epithelioid cell tumours (PEComas), melanotic Xp11 translocation renal cancers and melanotic Xp11 neoplasms. We have suggested that these tumours belong to a single clinicopathological spectrum. 'Xp11 neoplasm with melanocytic differentiation' or 'melanotic Xp11 neoplasm' have been proposed to designate this unique neoplasm. Herein, we describe the first case of an Xp11 neoplasm with melanocytic differentiation to be described in the prostate, bearing the novel NONO-TFE3 gene fusion. This study both adds to the spectrum regarding melanotic Xp11 neoplasms and expands its gene fusion spectrum. Moreover, we discuss the relationship of these rare tumours to neoplasms such as conventional PEComas, alveolar soft part sarcomas, malignant melanomas, clear cell sarcomas and Xp11 translocation renal cancers.

Melanotic xp11.2 neoplasm of the ovary: report of a unique case

We describe a primary ovarian neoplasm, occurring in a 15-year-old female patient, with morphologic, immunohistochemical, and molecular genetic features identical to those of the very rare tumors of the kidney previously described as "melanotic Xp11 translocation renal cancer." This represents, to the best of our knowledge, the first report of a melanotic Xp11 translocation-associated neoplasm arising outside of the kidney. We discuss the relationship of these rare tumors to neoplasms showing perivascular epithelioid cell differentiation, in particular those showing TFE3 rearrangements.

Pigmented perivascular epithelioid cell tumor (PEComa) of the kidney: a case report and review of the literature

Heavily pigmented perivascular epithelioid cell tumors (PEComa) are rare, only eight cases of which have been reported. Unlike typical epithelioid angiomyolipoma, most of these tumors have been encountered in female patients without tuberous sclerosis. The long-term prognosis thereof is undetermined. Cytological similarity and heavy melanin pigment make it difficult for pigmented PEComa to be differentiated from pigmented clear cell renal cell carcinoma or malignant melanoma. The immunoprofile of tumor cells, such as human melanoma black-45 expression, as well as the absence or presence of other melanocytic or epithelial markers, are helpful in determining a differential diagnosis. Here we report a case of heavily pigmented PEComa of the right kidney and review the literature describing this tumor. In this case, the immunoprofile and clinical features corresponded well to those described in the literature. Since the prognosis of such disease has not yet been established, close follow-up of this patient was recommended.

Pancreatic PEComa: a case report with ultrastructural localization of HMB-45 within melanosomes

PEComas (perivascular epithelioid cell tumors) represent a group of mesenchymal neoplasms showing characteristic morphologic, immunohistochemical, ultrastructural, and genetic features. These neoplasms are usually considered benign, being often well circumscribed by a thin capsule and showing scarce atypia. However, in some cases, they show local invasion and multiple metastases and cause the patient's death. PEComas have been found in many locations, but only 7 cases have been described in the pancreas to date. Here, the authors report an additional case of this rare neoplasm and demonstrate the HMB-45 immunoreactivity of melanosomes or premelanosomes at the ultrastructural level.

Malignant pigmented clear cell epithelioid cell tumor (PEComa) in an adolescent boy with widespread metastases: a rare entity in this age group

Malignant pigmented clear cell epithelioid cell tumor of the kidney is a rare variant of perivascular epithelioid cells tumors (PEComa) or epithelioid angiomyolipoma (AML). PEComa is characteristically composed purely of epitheloid cells. The fat cells and the blood vessels that are typical of classic AML are absent. Most epithelioid AML cases are benign; however, malignant epithelioid AML of the kidney has been occasionally reported in adults in association with tuberous sclerosis. We report the radiological-pathological features of a malignant pigmented clear cell epithelioid renal tumor in a 15-year-old boy presenting with extensive metastases but without clinical evidence of tuberous sclerosis.

Comparison of human glomerulus proteomic profiles obtained from low quantities of samples by different mass spectrometry with the comprehensive database

BACKGROUND

We have previously constructed an in-depth human glomerulus proteome database from a large amount of sample for understanding renal disease pathogenesis and aiding the biomarker exploration. However, it is usually a challenge for clinical research to get enough tissues for large-scale proteomic characterization. Therefore, in this study, we focused on high-confidence proteomics analysis on small amounts of human glomeruli comparable to those obtained from biopsies using different mass spectrometers and compared these results to the comprehensive database.

RESULTS

One microgram of human glomerular protein digest was analyzed each on five LC- combined mass spectrometers (LIT-TOF, LTQ-Orbitrap, Q-TOF, LIT and MALDI-TOF/TOF) yielding 139, 185, 94, 255 and 108 proteins respectively identified with strict criteria to ensure high confidence (> 99%) and low false discovery rate (FDR) (< 1%). An integrated profile of 332 distinct glomerular proteins was subsequently generated without discerned bias due to protein physicochemical properties (pI and MW), of which around 60% were detected commonly by more than two LC-MS/MS platforms. Comparative analysis with the comprehensive database demonstrated 14 proteins uniquely identified in this study and more than 70% of identified proteins in small datasets were concentrated to the top abundant 500 in the comprehensive database which consists of 2775 non-redundant proteins.

CONCLUSION

This study showed representative human glomerulus proteomic profiles obtained from biopsies through analysis of comparable amounts of samples by different mass spectrometry. Our results implicated that high abundant proteins are more likely to be reproducibly identified in multiple mass spectrometers runs and different mass spectrometers. Furthermore, many podocyte essential proteins such as nephrin, podocin, podocalyxin and synaptopodin were also identified from the small samples in this study. Bioinformatic enrichment analysis results extended our understanding of the major glomerular proteins about their subcellular distributions and functions. The present study indicated that the proteins localized in certain cellular compartments, such as actin cytoskeleton, mitochondrial matrix, cell surface, basolateral plasma membrane, contractile fiber, proteinaceous extracellular matrix and adherens junction, represent high abundant glomerular proteins and these subcellular structures are also highly significantly over-represented in the glomerulus compared to the whole human background.

Renal epithelioid angiomyolipoma with atypia: a series of 40 cases with emphasis on clinicopathologic prognostic indicators of malignancy

As epithelioid cellular morphology can be seen in clinically benign usual angiomyolipomas (AMLs), we divide epithelioid AMLs into those without and with atypia, the latter category associated in the literature with malignant potential. We herein report the histologic spectrum and biologic behavior of 40 consecutive cases of epithelioid AML with atypia and assess whether cases can be stratified prognostically based on clinical and pathologic features. Atypical epithelioid cells were defined as atypical polygonal cells with abundant cytoplasm, vesicular nuclei, prominent nucleoli, and nuclear size that exceeds x2 the size of adjacent nuclei. The degree of atypia was divided to moderate and severe. Cases with bland epithelioid cells with minimal variation in nuclear size were not included. Mean age was 50.5 years (range 17 to 81), and the female to male ratio was 1.6:1. Average tumor size was 7.2 cm (range 1.0 to 17.7). The percentage of epithelioid component ranged from 5%-100% (mean 68%). Of the epithelioid component, the percentage of cells exhibiting nuclear atypia ranged in individual cases from 5% to 100% (mean of 58.4% atypical cells); 26/40 (65%) cases showed severe nuclear atypia. Cells displaying severe nuclear atypia were typically of large size with abundant cytoplasm, compared with those with moderate atypia being of small to intermediate in size with scant to moderate amount of cytoplasm. Neoplastic multinucleated giant cells and necrosis was present in 22 cases (55%) and 15 cases (37.5%), respectively. Mitoses were identified in 72.5% (29/40) of cases and ranged from 1 to 6 per 10 hpf with 7 cases showing atypical mitotic figures. Lymphovascular invasion or renal vein invasion was present in 3 cases each. Hilar and perinephric fat involvement was present in 5 and 6 cases, respectively. Clinical follow-up was available in 34 out of the 40 cases. Of the 34 cases, 9 (26%) were malignant and showed local recurrence or distant metastases. Of the 9 patients with malignant tumors, 4 died of the disease at 6, 12, 15, and 34 months after the original diagnosis was rendered, and 4 were alive with disease (mean follow-up period of 52 mo, range 24 to 72 mo). Twenty-four patients showed no evidence of recurrence and/or metastases with a mean follow-up period of 34 months (range 1 to 156 mo). We compared the 21 cases of atypical epithelioid AMLs that exhibited a benign clinical course with a minimum follow-up period of 6 months postsurgery to the 9 cases with malignant behavior. All of these were more frequently observed in clinically malignant cases: older age, larger tumor size, higher percentage of epithelioid component, severe atypia, higher percentage of atypical cells, higher mitotic count, atypical mitotic figures, necrosis, lymphovascular invasion, and renal vein invasion. Using these features, we developed a predictive model of 4 atypical features that included: (1) > or =70% atypical epithelioid cells, (2) > or =2 mitotic figures per 10 hpf, (3) atypical mitotic figures, and (4) necrosis; the presence of 3 or all of the features was highly predictive of malignant behavior. This model accurately categorized 78% of clinically malignant and 100% of the clinically benign epithelioid AMLs with atypia.

Renal epithelioid angiomyolipoma: a study of six cases and a meta-analytic study. Development of criteria for screening the entity with prognostic significance

AIMS

Renal epithelioid angiomyolipoma (EAML) is only described in case reports or in multi-institutional small series. The aim was to report cases seen at our institution and to perform a meta-analysis based on a literature review.

METHODS AND RESULTS

Six EAML cases seen at our institution were reviewed and a meta-analysis performed using cases retrieved from a literature review. There were a total of 69 cases for review. The male:female ratio was 1:3. In the absence of areas of typical AML, useful features in distinguishing EAML from epithelial renal neoplasms include: extreme degree of cytological atypia, histiocytoid appearance, presence of melanocytic pigments, solid architecture with the absence of frequent areas of alveolar pattern, tubulo-papillary formation and scarring. A fatal outcome, distant or lymph node metastasis, venous invasion and local recurrence were considered as adverse events and occurred in 40% of cases over a period of follow-up of 3-60 months (mean 22.5 +/- 18 months). Tumours with an unfavourable outcome showing marked cytological atypia and extensive tumour necrosis were larger (135 +/- 43 mm) than those with a favourable outcome (79 +/- 50 mm) (P < 0.002), and predominantly occurred in men.

CONCLUSIONS

Renal neoplasms with certain unusual features should be investigated immunohistochemically to rule out the possibility of EAML. The frequency of adverse outcome is lower in EAML than in renal cell carcinoma.

Pigmented perivascular epithelioid cell tumor of the kidney

A case of pigmented perivascular epithelioid cell tumor of the kidney in a 57-year-old woman with a clinically indicated tuberous sclerosis is presented. The lesion was a 3.0-cm, well-demarcated, black-colored mass. The tumor was histologically characterized by an epithelioid arrangement of round to polygonal cells with round nuclei and clear cytoplasm containing abundant melanin. Tumor cells showed mild atypia and low mitotic activity. A spindle cell proliferation was focally observed. There were no adipose elements or thick-walled vascular vessels. The stroma demonstrated intervening, thin, fibrovascular septa. Immunohistochemically, the tumor cells were strongly positive for HMB-45 but negative for epithelial and muscle markers, vimentin, and S100 protein. The patient had no evidence of disease 3 months after surgery. Pathologists and clinicians should know about the existence of pigmented perivascular epithelioid cell tumor of the kidney. This type of tumor should be differentiated from clear cell renal cell carcinoma or malignant melanoma.

The Evolving Concept of Renal Neoplasia: Impact of Emerging Molecular and Electron Microscopic Studies

The classification of renal tumors has evolved from one that initially encompassed only 2 types of tumors, i.e., clear and granular cell carcinomas, to the markedly expanded recent classification that incorporates new entities, some of which are primarily defined by specific molecular abnormalities. Despite these advances, a single tumor category, clear cell carcinoma, still incorporates the majority (approximately 70%) of renal tumors. It is, however, postulated that this single category is likely to encompass several different tumor types that are, at present, undifferentiated. Electron microscopic studies have been pivotal in defining the spectrum of oncocytoma-chromophobe renal cell carcinoma. Cytoplasmic eosinophilia found in some renal cell carcinomas currently classified as clear cell type is under intense study. Tumors that have recently emerged from this group include tumors with translocations involving chromosome Xp11.2, carcinomas associated with neuroblastoma and epithelioid angiomyolipoma. The spectrum of renal tumors seen in younger patients is wider than among older patients, with rare and unusual tumors being more likely seen in younger patients. The author concludes that although the routine application of electron microscopy to kidney tumor diagnosis may not be practical, systematic ultrastructural studies of these tumors may aid in the definition of new entities.

Melanotic Xp11 translocation renal cancers: a distinctive neoplasm with overlapping features of PEComa, carcinoma, and melanoma

We describe 2 cases of malignant melanotic epithelioid renal neoplasms bearing TFE3 gene fusions. Both neoplasms occurred in children (an 11-y-old boy and a 12-y-old girl), and presented with disseminated metastatic disease including mediastinal and mesenteric adenopathy. Both neoplasms featured sheets of epithelioid cells with clear to finely granular eosinophilic cytoplasm set in a branching capillary vasculature. The neoplastic cells contained variable amounts of finely brown pigment confirmed to be melanin by histochemical stains. By immunohistochemistry, the neoplastic cells labeled for melanocytic markers HMB45 and Melan A, but not for S100 protein, MiTF, or any epithelial marker (cytokeratins, epithelial membrane antigen), renal tubular marker (CD10, PAX8, PAX2, RCC Marker) or muscle marker (actin, desmin). Both neoplasms demonstrated nuclear labeling for TFE3 protein by immunohistochemistry, and the presence of TFE3 gene fusions was confirmed by TFE3 fluorescence in situ hybridization analysis. These distinctive neoplasms combine morphologic features of perivascular epithelioid cell neoplasms (PEComas), Xp11 translocation carcinoma, and melanoma, though the phenotype most closely approaches PEComa. These neoplasms represent the first documented examples in which TFE3 gene fusions coexist with melanin production, and their identification raises the possibility that TFE3 gene fusions may underlie an aggressive subset of lesions currently classified as PEComa in young patients.

The use of the Ki-67 marker in the pathological diagnosis of the epithelioid variant of renal angiomyolipoma

OBJECTIVE

Epithelioid angiomyolipoma (EAML) is a rare malignant variant of renal angiomyolipoma (AML). There were 34 cases of EAML reported in 25 studies (including this present study) over the past decade. About 68% were females and 32% males. The mean age was 40.1 years, 53% developed metastatic disease after nephrectomy, and eight patients had TSC. All cases are reported positive when stained with HMB-45 which also labels all classical AML. This study evaluates the use of Ki-67 (proliferation marker) in the pathological diagnosis of EAML and distinction from classical AML.

METHOD

Immunohistochemical reactions for Ki-67 were generated on multiple representative blocks of tissue obtained from two cases of HMB-45 positive EAML and four cases of classic AML and the percentage of positively staining cells estimated.

RESULTS

Both cases of EAML were strongly positive for Ki-67 while all four classic AML were completely negative.

CONCLUSION

The Ki67 is a useful marker in which distinguishes the malignant epithelioid variant of AML from classic AML.

Heavily Pigmented Renal Cell Carcinoma: A Case Report, With Review of the Literature and Differential Diagnosis

Clear cell carcinoma is the most common histotype among renal cell tumors. The prominent vascular network of sinusoidal vessels lined by delicate endothelial cells may often lead to hemorrhagic areas with secondary deposition of chunky birefringent hemosiderin granules. The finding of pigmentation other than iron, and in particular melanin deposits, in renal tumors is a rare occurrence that should lead to differential diagnosis with other primary and metastatic tumors of the kidney.

Perivascular epithelioid cell tumor of the rib

We present a rare case of perivascular epithelioid cell tumor (PEComa) in the right 6th rib of a 28-year-old man. A plain computed tomography scan showed a round osteolytic lesion in the right 6th rib. The resected tissue contained a globular-shaped, soft tumor. Histologically, the tumor was rich in vasculature and exclusively composed of perivascular epithelioid cells with clear cytoplasm. Immunohistochemically, the tumor expressed diffusely a melanocyte marker, human melanoma black-45, and focally a myogenic marker, alpha-smooth muscle actin, but not an epithelial marker, AE1/AE3. Fontana-Masson-positive melanin pigments were present and c-kit receptor tyrosine kinase (CD117), involved in the development of melanocytes but not myogenic cells, was expressed in tumor cells. These findings indicate that the tumor is PEComa with some differentiation into melanocytes. Notably, owing to the unique location of the occurrence, the tumor occupied bone marrow tissues of the rib, resulting that the tumor has the potential for hematogenous metastasis. In spite of the lack of cells with severe atypia, necrosis, and numerous mitoses, tumor cells invaded into surrounding tissues and overexpressed cyclin D1. To the best of our knowledge, this is the first case report of PEComa arising from the rib with the signs of malignant potential.

Perivascular epithelioid cell tumour (PEComa) of the soft tissue

AIMS

PEComa is a rare tumour developing from perivascular epithelioid cells (PEC) and is characterised by positive immunoreactivity for HMB45. Since PEComas are tumours having both a spindle cell component and an epithelioid and giant cell component, as seen in many sarcomas, as well as having a wide distribution in various organs and soft tissue, we reviewed cases originally diagnosed as sarcomas of the soft tissue in our institution and screened them by immunostaining for HMB45.

METHODS

Consecutive soft tissue sarcomas (31 tumours) retrieved from the Surgical Pathology file at our institution for a period of 3 years were submitted for immunostaining for HMB45. Cases with positive HMB45 immunostaining were submitted for further immunostaining for MART1, CD68, S100 protein, cytokeratin AE1/3, EMA, vimentin, MSA and CD117.

RESULTS

Of 31 sarcomas, three tumours in the group of 11 malignant fibrous histiocytomas (MFH) and unclassified sarcomas showed positive immunoreactivity for HMB45 and MART1 in 1-25% of tumour cells. The three tumours were located in the lower extremities and measured 8, 11 and 12 cm in diameter. Patient gender male:female was 2:1 and ages were 46, 56 and 60 years. Microscopically, the tumours were composed of a variable proportion of spindled cells, multinucleated cells and epithelioid cells disposed in diffuse sheets or nests. Mitotic figures and necrosis were frequent. The immunoreactivity was diffuse for CD68, focal for AE3 and EMA, negative or focal for MSA and CD117, and negative for S100 and AE1. All three patients developed lymph node or distant metastases and died of the disease within 1-2 years.

CONCLUSIONS

PEComa re-screened from the group of high grade sarcomas without definite differentiation range from pleomorphic to monomorphic cytohistopathological features. Immunostaining for HMB45 of unclassified sarcomas is useful for the classification of these tumours. They occur preferentially in the lower extremities and have a high malignant potential when associated with large size, tumoural necrosis and high mitotic activity.

Giant Cells: Contradiction to Two-Hit Model of Tuber Formation?

Tuberous sclerosis (TSC) is an autosomal dominant disease characterized by the formation of hamartomatous lesions in many organs, including brain, heart or kidneys. It has been found that TSC is caused by the mutation in one of the two tumor suppressor genes: TSC1 or TSC2, encoding hamartin and tuberin, respectively. According to Knudson's two-hit model of tumorigenesis, second-hit mutation and resulting loss of heterozygosity (LOH) of a tumor suppressor gene is necessary for tumor formation. In fact, LOH is commonly found in several types of hamartomas formed in the process of tuberous sclerosis, but, interestingly, not in brain lesions, containing characteristic giant cells. In this paper, we review literature covering origination of giant cells and present several hypotheses explaining why in spite of the presence of hamartin and tuberin, brain lesions form in TSC patients.

C-Kit-positive metastatic malignant pigmented clear-cell epithelioid tumor arising from the kidney in a child without tuberous sclerosis

We report the first pediatric case of malignant pigmented epithelioid clear-cell tumor arising from kidney; the lesion occurred in a 12-year-old girl without tuberous sclerosis. The tumor was widely metastatic to the retroperitoneum and chest, and the patient died of the disease 9 months after diagnosis, despite active chemotherapy. Pigmented epithelioid clear-cell tumor of the kidney is a rare variant of epithelioid angiomyolipoma and a member of the family of perivascular epithelioid cell tumors (PEComas). The tumor demonstrated overlapping features between clear-cell sugar tumor and epithelioid variant of angiomyolipoma. Tumor cells were positive for HMB-45 expression, negative for any evidence of muscular differentiation, and contained melanin pigment and premelanosomes in the cytoplasm. Diffuse C-Kit (CD117) positivity was identified throughout the tumor. This is the first report of C-Kit-positive malignant PEComas.

[Tumors of the kidneys: new entities]

Since 1998 new entities have surfaced in renal tumor classification and have been included in the WHO 2004 classification. In this article, we will discuss the following entities: multilocular clear cell renal carcinoma, Xp11 translocation carcinoma, low grade mucinous tubular carcinoma, epithelioid angiomyolipoma, benign mixed epithelial and stromal tumor. We will investigate new concepts of hybrid oncocytoma and chromophobe renal cell carcinoma and the syndrome of Birt-Hogg-Dube which is associated to kidney tumors. At least, we will touch on new elements in the Bellini carcinoma definition.

Giant Cells: Contradiction to Two-Hit Model of Tuber Formation?

1. Tuberous sclerosis (TSC) is an autosomal dominant disease characterized by the formation of hamartomatous lesions in many organs, including brain, heart or kidneys. It has been found that TSC is caused by the mutation in one of two tumor suppressor genes: TSC1 or TSC2, encoding hamartin and tuberin, respectively. 2. According to Knudson's two-hit model of tumorigenesis, second-hit mutation and resulting loss of heterozygosity (LOH) of a tumor suppressor gene is necessary for tumor formation. In fact, LOH is commonly found in several types of hamartomas formed in the process of tuberous sclerosis, but, interestingly, not in brain lesions, containing characteristic giant cells. 3. In the present paper we review literature covering origination of giant cells and present several hypotheses explaining why in spite of the presence of hamartin and tuberin, brain lesions form in TSC patients.

Lack of response of a metastatic renal perivascular epithelial cell tumor (PEComa) to successive courses of DTIC based-therapy and imatinib mesylate

An 11 year-old girl presented with two large abdominal masses in the left flank and epigastrium and left supraclavicular lymphadenopathy. Subsequent investigations led to the diagnosis of metastatic perivascular epithelioid cell tumor (PEComa) arising from the left kidney. Effective treatment for this rare tumor is not yet known. The tumor did not respond to an initial treatment of two cycles of a dacarbazine (DTIC) based regimen. She was placed on a trial of imatinib mesylate based on tumor expression of c-KIT, a tyrosine kinase targeted by this drug. This report highlights the first documented case of the use of imatinib for PEComa. Lack of response and adverse effects of the drug required discontinuation of therapy.

Perivascular epithelioid cell tumor of the orbit: a case report and review of the literature

We present a unique case of a perivascular epithelioid cell tumor (PEComa) in the orbit of a 9-year-old female patient. The entity of PEComas has been described only recently. Characteristic histologic features and an immunohistochemical profile of negativity for epithelial markers and positivity for melanogenesis-related markers define the tumors. In children and young adults, this tumor has a predilection for the falciform ligament and ligamentum teres of the liver. It is associated with, but not exclusive to, tuberous sclerosis. To the best of our knowledge, this is the first reported case of a PEComa of the orbit in a child or adult. The main differential diagnoses for this melanin pigment-producing lesion include melanoma and pigmented paraganglioma. The histologic features, immunohistochemical profile, ultrastructural studies, and molecular studies led us to favor a diagnosis of PEComa. The prognosis of this entity is undetermined due largely to the small number of reported cases.

Triple synchronous neoplasms in one kidney: report of a case and review of the literature

We report the case of a patient with three synchronous but histologically different primary renal tumors that were all in the same kidney. Two tumors were different subtypes of renal cell carcinoma (RCC), and the third was a variant form of angiomyolipoma. The patient was a 62-year-old man who was receiving antihypertensive drugs and came to our hospital for a regular check-up. Ultrasonography performed during the visit revealed a left renal mass, but the patient had no related symptoms. Subsequent computed tomography revealed two round, high-density masses, one in the mid-portion and the other in the lower pole of the left kidney, and multiple cysts in the right kidney and the liver. The mass in the mid-portion measured 3.3 x 3.0 x 2.8 cm, and the mass in the lower pole measured 1.7 x 1.1 x 0.9 cm. A left radical nephrectomy was performed. On gross examination, an additional ovoid nodule (0.6 cm in the greatest dimension) was found in the lower pole. Microscopically, the largest tumor consisted of a broad alveolar arrangement of large round cells with abundant eosinophilic or clear cytoplasm, distinct cell borders, and perinuclear halos, features consistent with chromophobe RCC. The smallest tumor was a conventional (clear-cell) RCC. The third tumor was composed solely of atypical epithelioid cells with prominent nucleoli and yellowish-brown to black pigments. The tumor cells were positive for melanin (Fontana-Masson stain), the melanoma marker HMB45, vimentin, smooth-muscle actin, and the macrophage marker CD68 and were negative for cytokeratin. This tumor was considered a pigmented epithelioid type of angiomyolipoma. The histologic, histochemical, and immunohistochemical features in this case confirmed the presence of three synchronous primary tumors, a chromophobe and a clear-cell type RCC and a pigmented epithelioid angiomyolipoma, all of which were in the same kidney. This case is the first of its type reported in the literature.

Heavily melanotic perivascular epithelioid clear cell tumor of the kidney

A black-colored and well-circumscribed renal tumor in a 71-year-old woman is reported. The tumor was unique in that it was rich in vasculature and exclusively composed of perivascular epithelioid clear cells. Morphological features were reminiscent of conventional renal cell carcinoma (RCC). However, immunohistochemical examinations showed that the tumor cells did not express any epithelial markers, but diffusely and intensely expressed a melanocytic marker, gp-100/HMB-45. Another striking feature of the tumor was a large amount of cytoplasmic pigment that made the tumor wholly black. The pigment was not stained with Berlin-blue, completely bleached with potassium permanganate, and stained with Fontana-Masson staining, which suggests that the pigment was melanin. Morphological features and immunohistochemical findings indicated that the present tumor was an extreme example of a perivascular epithelioid clear cell tumor with a large amount of melanin, which has not been previously reported. One should be aware of the pure form of perivascular epithelioid clear cell tumor of the kidney because it is sometimes very difficult to differentiate this tumor from conventional RCC. Immunohistochemical examinations and the presence of cytoplasmic melanin can help the differentiation.

Perivascular epithelioid cell tumor of the jejunum

Certain HMB-45-positive epithelioid cell tumors have recently been categorized under a unified concept: perivascular epithelioid cell tumor (PEComa). In this report, we describe ajejunal PEComa arising in a 32-year-old woman without other tumors or stigmata of tuberous sclerosis. The tumor consisted of nests of epithelioid cells with clear to granular eosinophilic cytoplasm. The nests were separated by thin fibrovascular septa. The tumor cells were positive for HMB-45 and progesterone receptor, and negative for cytokeratin, epithelial membrane antigen, vimentin, desmin, alpha-smooth muscle actin and CD34. RT-PCR analysis failed to reveal fusion transcript ETW/ATF1, which is characteristic of clear cell sarcoma of the soft parts. She developed a recurrent tumor at the pelvic wall and the left ovary at 13 and 25 months after the first operation, respectively. Each tumor was resected surgically, and no additional therapy was performed. We think the tumor of this case is a malignant form of PEComa because of the clinical history of multiple recurrences and the size of the primary tumor. Our case underscores that to make a correct diagnosis, clinical information and immunohistochemical examination are essential.

[Sugar tumor. Rare differential diagnosis of pulmonary clear cell tumor after renal carcinoma]

Pulmonary clear cell or sugar tumor is a rare entity of unknown etiology and histogenesis. As primary extrapulmonal sugar tumor (PEST) this neoplasia can also be found in the trachea, vulva, rectum, pancreas or atrial-septal region. So far about 40 case reports have been published in english literatur. We present the case report of a patient with a pulmonal sugar tumor, who previously underwent nephrectomy because of clear cell renal carcinoma. Clinical aspects, differential diagnosis, therapy and histogenetic aspects are discussed.

Oncocytic angiomyolipoma of the kidney: a case report

We describe a case of oncocytic angiomyolipoma composed of polygonal eosinophilic cells, that shares many features with renal oncocytoma. It was composed of alveolar structures, with accumulation of foamy histiocyte-like cells surrounding large globules of acellular, nonfibrillary, densely eosinophilic basal membrane-like substance. Immunohistochemically, there was focal reactivity for HMB45 and negativity for the epithelial markers. Oncocytic angiomyolipoma lacks the atypical features of the recently described epithelioid variant of angiomyolipoma. None of the reported cases have been associated with tuberous sclerosis.

Pediatric liver tumors and hepatic ontogenesis: common and distinctive pathways

Several types of pediatric liver tumors exhibit structural features apparently reflecting processes which normally occur during hepatic ontogenesis: some hepatoblastomas mimic distinct phases of hepatogenesis, including the formation of mesenchymal structures closely associated with immature epithelia, and there are tumors almost exclusively consisting of complex mesenchymal patterns. Current classifications of hepatoblastomas refer to the identification of more or less mature (differentiated) single or mixed components seen in histologic preparations. These do not, however, attempt to integrate ontogenic pathways, in contrast for example, to nephroblastoma and associated lesions, where such a view has proved to be highly fruitful. Based on the fact that an enormous amount of knowledge has recently been accumulated regarding hepatic ontogenesis, time may have come to look at these tumors with a new eye. In what follows, we aim at trying to analyze distinct features of pediatric hepatic tumors (except vascular tumors) within the background of ontogenesis. Some key steps of hepatogenesis and the regulatory factors involved may, in the future, deliver an armamentarium to search for novel molecular mechanisms involved in tumorigenic pathways.

Monotypic angiomyolipoma of the nasal cavity: a heretofore undescribed occurrence

A monotypic angiomyolipoma of the nasal cavity in a 34-year-old woman is described. Tumor cells were spindled or epithelioid and contained glycogen and diastase-resistant PAS-positive granules. There were few mitoses, and necrosis was absent, indicating a benign tumor. The stroma was markedly vascular, and a few adipocytes were seen in one area. Cells were positive for melanocyte and muscle markers. Electron microscopy revealed abundant dense granules. Although melanin was absent histochemically, it was present using a chemical assay, and the granules may, therefore, be atypical melanosomes. Fine actin filaments, attachment plaques and lamina were present. Initial assessment of the lesion indicated malignant melanoma, but the immunostaining and histologic features indicated monotypic angiomyolipoma. To the best of our knowledge, this is the first such case in the nasal cavity.

Abdominopelvic sarcoma of perivascular epithelioid cells. Report of four cases in young women, one with tuberous sclerosis

The perivascular epithelioid cell has been proposed to be the unifying proliferating cell type in a number of lesions such as angiomyolipoma, lymphangiomyomatosis, clear cell "sugar" tumor and renal capsuloma. With the exception of rare examples of angiomyolipoma, they are non-metastasizing. We report four examples of a new member of this family of perivascular epithelioid cell neoplasms that occur in abdominopelvic location and show metastatic properties. The patients, all women, were aged 19 to 41 years (mean, 32), and presented with a tumor mass involving the serosa of the ileum, uterus or pelvic cavity. Morphologically, the tumors were composed of sheets of large polygonal cells with glycogen-rich clear or eosinophilic cytoplasm and moderately pleomorphic nuclei, traversed by a delicate vasculature, mimicking clear cell carcinoma. There were areas of coagulative necrosis and occasional mitotic figures. Intracytoplasmic brown pigment was present in two cases. Spindly cells, smooth muscle and fat were absent. Lymphovascular invasion was present in all, lymph node metastasis was documented in two and metastasis to the ovary was present in one case. Two patients developed widespread metastatic disease after 10 and 28 months from diagnosis. One patient showed the clinical signs of tuberous sclerosis. In spite of the epithelial-like appearance, the tumor cells were negative for epithelial markers but were strongly positive with the melanogenesis-related marker HMB45. Another melanogenesis marker (MART-1) was positive in two cases. Other markers including S-100 protein, vimentin, muscle-specific actin, desmin and chromogranin A were negative. Thus, these tumors are not readily classifiable in the existing schema of known entities, and show overlapping morpho-phenotypic features of clear cell "sugar" tumor of the lung and epithelioid angiomyolipoma. We consider them as sarcomas composed of a pure population of uncommitted perivascular epithelioid cell, that lack modulation toward smooth muscle or adipose cells.

Primary extrapulmonary sugar tumor (PEST): a report of four cases

The cell of origin and direction of differentiation of the clear cell tumor of the lung (the so-called sugar tumor) remains enigmatic. Recognition of HMB-45 immunoreactivity and identification of melanosomes have suggested a relationship to angiomyolipoma of kidney or liver and lymphangiomyoma. This has given rise to the concept that clear cell tumors are neoplasms of so-called perivascular epithelioid cells--PEComas. Herein we report the existence of four similar tumors occurring in extrapulmonary sites, one of which had malignant features. The three benign tumors occurred in females ages 9, 20, and 40 years; two were located in the rectum and one in the vulva. The malignant tumor occurred in the inter-atrial cardiac septum of a 29-year-old man. Common histologic features were a richly vascular organoid architecture, tumor cells with clear to pale eosinophilic cytoplasm, abundant glycogen, and immunoreactivity for HMB 45, but not S100, multiple keratin, neuroendocrine, or muscle markers. Benign tumors demonstrated low mitotic activity, no necrosis, and good circumscription; the malignant tumor showed considerable mitotic activity, necrosis, and an infiltrative growth pattern. Ultrastructurally, glycogen was present, mitochondria were abundant, and membrane-bound lamellated bodies consistent with premelanosomes were present in two cases, and equivocal in one. Because these tumors have light microscopic, immunohistochemical, and electron microscopic features similar to pulmonary sugar tumors, we propose the name primary extrapulmonary sugar tumor (PEST) for them. Although most PEST's are probably benign, malignant forms appear to exist. These cases further support the concept of a family of systemic HMB-45 positive tumors that include sugar tumors, angiomyolipoma of kidney or liver, lymphangiomyomas, and clear-cell myomelanocytic tumors of the falciform ligament/ligamentum teres.