Renal angiomyolipoma is a benign mesenchymal initially described by Grawitz et al. in 1900. Represent approximately 1% of renal tumors surgically removed. That was also described by Bourneville and Brissaud as part of tuberous sclerosis complex (TSC) at the same time. Hartwick et al. reported in 1989 an epithelioid angiomyolipoma with unusual histologic patterns mimicking malignancy after further investigation has revealed malignant characteristics in some cases. Has recently been classified as a variant of angiomyolipoma with malignant potential.
Pathology
Grossly, renal angiomyolipoma are large lesions, the mass of yellow-gray, well demarcated from the kidney, but not truly encapsulated. They are usually solitary, but if present in multiple numbers, the image is of a dominant tumor associated with minor injuries. As they grow, they cause a mass effect rather than infiltrating the surrounding tissue. They consist of a variable proportion of thick-walled blood vessels, poorly organized smooth muscle bundles and mature adipose tissue, and the variable proportion of each component accounts for the appearance of the lesion. Smooth muscle cells are often spindle-shaped epithelioid and occasionally rounded. regional lymph nodes are considered to represent multicentric involvement site of metastasis. Rarely, direct extension of tumor to the inferior vena cava and renal venous system in the absence of distant metastasis has been described.
The higher prevalence of angiomyolipoma in women has increased speculation that there may be a sex enhancement of growth hormone angiomyolipoma. Progesterone and estrogen receptors have been detected in these tumors, together with reports of rapid growth during pregnancy.
The immunohistochemical profile is characterized by co-expression of melanocytic (for example, HMB-45) and smooth muscle (smooth muscle actin, for example) markers. It can also be positive for CD68, neuron specific enolase, S-100, desmin, and hormone receptors, whereas epithelial markers were always negative.
Two genes are known to cause tuberous sclerosis, a gene TSC (TSC1) on chromosome 9q34, encoding hamartin, and TSC2 on chromosome 16p13, which produces tuberin, a protein active GTPase. The biology of these genes has been elucidated extensively in recent years. Angiomyolipoma frequently have a loss of heterozygosity one of the two TSC loci in both sporadic tumors associated with tuberous sclerosis.
Epithelioid angiomyolipoma is a potentially malignant mesenchymal neoplasm closely related to classic angiomyolipoma. There is a higher association (> 50%) with tuberous sclerosis. Patients are usually symptomatic, both sexes are equally affected, and the mean age of onset (38 years) is generally younger compared to classic angiomyolipoma. The lack of fat makes it more difficult radiological diagnosis. About a third of cases of epithelioid angiomyolipoma metastasize to lymph nodes, liver, lungs, or spine.
Pathology
Grossly, renal angiomyolipoma are large lesions, the mass of yellow-gray, well demarcated from the kidney, but not truly encapsulated. They are usually solitary, but if present in multiple numbers, the image is of a dominant tumor associated with minor injuries. As they grow, they cause a mass effect rather than infiltrating the surrounding tissue. They consist of a variable proportion of thick-walled blood vessels, poorly organized smooth muscle bundles and mature adipose tissue, and the variable proportion of each component accounts for the appearance of the lesion. Smooth muscle cells are often spindle-shaped epithelioid and occasionally rounded. regional lymph nodes are considered to represent multicentric involvement site of metastasis. Rarely, direct extension of tumor to the inferior vena cava and renal venous system in the absence of distant metastasis has been described.
The higher prevalence of angiomyolipoma in women has increased speculation that there may be a sex enhancement of growth hormone angiomyolipoma. Progesterone and estrogen receptors have been detected in these tumors, together with reports of rapid growth during pregnancy.
The immunohistochemical profile is characterized by co-expression of melanocytic (for example, HMB-45) and smooth muscle (smooth muscle actin, for example) markers. It can also be positive for CD68, neuron specific enolase, S-100, desmin, and hormone receptors, whereas epithelial markers were always negative.
Two genes are known to cause tuberous sclerosis, a gene TSC (TSC1) on chromosome 9q34, encoding hamartin, and TSC2 on chromosome 16p13, which produces tuberin, a protein active GTPase. The biology of these genes has been elucidated extensively in recent years. Angiomyolipoma frequently have a loss of heterozygosity one of the two TSC loci in both sporadic tumors associated with tuberous sclerosis.
Epithelioid angiomyolipoma is a potentially malignant mesenchymal neoplasm closely related to classic angiomyolipoma. There is a higher association (> 50%) with tuberous sclerosis. Patients are usually symptomatic, both sexes are equally affected, and the mean age of onset (38 years) is generally younger compared to classic angiomyolipoma. The lack of fat makes it more difficult radiological diagnosis. About a third of cases of epithelioid angiomyolipoma metastasize to lymph nodes, liver, lungs, or spine.
Microscopically there are layers of epithelioid cells with abundant eosinophilic granular cytoplasm, enlarged vesicular nuclei and prominent nucleoli. Classic angiomyolipoma areas can be found interspersed focal. Tumors with necrosis, increased mitotic activity, nuclear atypia, and infiltration into surrounding tissues should be considered potentially malignant. The immunohistochemical profile positive for melanocytic markers as HMB-45, but not always positive for smooth muscle markers such as actin. Although rare angiomyolipoma, epithelioid should be kept in perspective, when the diagnosis of angiomyolipoma was made.
to be continued to part 2
to be continued to part 2