Epithelioid Angiomyolipoma: A Case Report

HMB45 and Melan-A Expression in Renal Angiomyolipoma and Their Significance for the Diagnosis

Aims and Background

The melanosome-associated proteins, also called HMB45 and melan-A, are also present in renal angiomyolipoma. The aim of the present study was to evaluate the expression of HMB45 and melan-A in mesenchymal cells of renal angiomyolipoma and to investigate their significance in the differential diagnosis.

Methods

Twelve patients, 9 females and 3 males diagnosed with renal angiomyolipomas, were included in the present study. The most representative tumor tissue block was chosen from each case, and 5-üm sections were taken to poly-l-lysin-coated slides for immunohistochemical staining. The standard streptavidin-biotin immunoperoxidase method was used for immunostaining with HMB45 and melan-A antibodies.

Results

All of the cases showed positive cytoplasmic immunostaining for HMB45 and melan-A. Melan-A expression was shown in smooth muscle component, adipose tissue and predominantly in the perivascular cells, whereas HMB45 immunoreactivity was stronger than melan-A expression in all cases.

Conclusions

It was concluded that HMB45 and melan-A reactivity is a useful tool to distinguish renal angiomyolipomas from other primary and secondary mesenchymal and primary epithelial tumors. Melan-A and HMB45 share similar specificities for renal angiomyolipoma. In addition, such expression in renal angiomyolipomas may occur without any evidence of nevomelanocytic differentiation. Further research is required to determine the histogenesis of this entity.

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.

Acute abdomen as an unusual presentation of hepatic PEComa. A case report

Perivascular epithelioid cell (PEC) tumors (or PEComas) are myomelanocytic lesions defined by coexpression of melanocytic and muscle markers, suggesting dual differentiation. They are rare mesenchymal tumors and include subtypes with distinct clinical features: angiomyolipoma, lymphangioleiomyomatosis, and clear cell "sugar" tumors of the lung, pancreas and uterus. Consequent upon the World Health Organization's recognition of PEC-derived tumors as a distinct entity, an increasing number of reports has documented PEComas arising at various anatomical locations. Clear cell myomelanocytic tumors of the falciform ligament/ligamentum teres (CCMTs) represent a rare variant of the PEComas. These hepatic PEComas, different from angiomyolipoma of the liver, pose a clinical, radiological and morphological diagnostic challenge. Because of their rarity, the clinical features and biological behavior of these tumors have yet to be established. We experienced our first case of CCMT in a 36-year-old woman who presented to our emergency department with a 3-day history of abdominal discomfort and progressive growth of an epigastric bulk. Intralesional hemorrhage was causing abdominal distension, which progressed to acute abdomen soon after. The hemoglobin concentration was 9.9 g/dL. Liver laboratory tests showed slight elevation of AST, ALT and gamma-GT. The alpha-fetoprotein level was not elevated. The radiological images showed a hemorrhagic mass with some bizarre features in left hepatic lobe, immediately adjacent to the ligamentum teres and falciform ligament. The patient underwent a left hepatic lobectomy. The diagnosis of CCMT was based on histological and immunohistochemical staining. The postoperative course was uneventful. The patient received no adjuvant treatment and is currently, 34 months after surgery, alive and disease free. In this report we describe a peculiar and hitherto undescribed clinical presentation of this tumor and its further course. Moreover, we discuss previously undescribed diagnostic imaging. We recommend that all unusual carcinomas and mesenchymal tumors of the liver should be tested for HMB-45: when positive, there is a high likelihood of PEComa.

Epithelioid angiomyolipoma of the kidney

Epithelioid angiomyolipoma is a recently recognized variant of angiomyolipoma, which is characterized by the presence of polygonal cells with densely eosinophilic cytoplasm and varying degrees of nuclear atypia. Only a relatively small number of cases of epithelioid angiomyolipoma of the kidney have been reported in the literature. We report a case of epithelioid angiomyolipoma of the kidney that occurred in a 38-year-old woman. The tumor was composed of diffuse sheets of epithelioid cells, adipocytes and only scattered thick-walled blood vessels. The epithelioid cells had pleomorphic and hyperchromatic nuclei with densely eosinophilic cytoplasm. Hemorrhage, necrotic foci and clusters of foamy macrophages were present. HMB-45, CD117 (c-kit) and CD68 were detected in the epithelioid cells. There was no expression of cytokeratin, epithelial membrane antigen or desmin. The patient showed no evidence of recurrence or metastatic disease 9 months after nephrectomy.