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Podoplanin, which is immunoreactive to D2-40 antibody, is reportedly expressed in lymphatic vessels in non-neoplastic tissues, and also in vascular and non-vascular tumors. However, its expression in non-neoplastic and neoplastic liver tissues has not been well documented. In this study, we examined podoplanin expression in specimens from 10 normal livers and 73 cases of liver tumors: hemangioma (16 cases), epithelioid hemangioendothelioma (9 cases), angiosarcoma (4 cases), angiomyolipoma (7 cases), hepatocellular carcinoma (11 cases), intrahepatic cholangiocarcinoma (11 cases), and metastatic liver cancer (15 cases). We compared levels of podoplanin and other endothelial markers (CD31, CD34, and factor VIII) in liver tumors. In the normal liver, podoplanin was expressed in lymphatic endothelium, nerve fibers, and mesothelium in the hepatic capsule, but not observed in any cells within hepatic lobules. Among liver tumors, podoplanin was specifically expressed in seven of nine cases (78%) of epithelioid hemangioendothelioma but not in other hepatic tumors. The expression of CD31, CD34, and factor VIII was observed in endothelial cells in all cases of hemangioma, epithelioid hemangioendothelioma, angiosarcoma, and angiomyolipoma with one exception, a case of epithelioid hemangioendothelioma which was without CD31 expression. Interestingly, the intensity of podoplanin expression was negatively correlated with the expression of CD34 and factor VIII. In conclusion, podoplanin would be useful as a diagnostic marker for epithelioid hemangioendothelioma in liver tumors.

Lymphangioleiomyomatosis is a progressive lung disease characterized by a diffuse proliferation of pulmonary smooth muscle cells and cystic degeneration. Lymphangioleiomyomatosis can occur either independently of other disease or in association with tuberous sclerosis complex, a tumor-suppressor gene syndrome caused by mutations that inactivate either TSC1 or TSC2. TSC2 mutations and loss of heterozygosity have been identified in sporadic lymphangioleiomyomatosis-associated angiomyolipomas, thus implicating the TSC/Ras homolog-enriched in brain (Rheb)/mammalian target of Rapamycin (mTOR)/p70 S6 kinase signaling pathway in their pathogenesis. This study was undertaken to determine whether the mTOR/p70 S6 kinase signaling pathway is activated in lymphangioleiomyomatosis-associated angiomyolipomas lacking TSC1/TSC2 loss of heterozygosity. Phospho-ribosomal protein S6 (Ser235/236) immunohistochemistry was performed on five lymphangioleiomyomatosis-associated angiomyolipomas, two matched lymphangioleiomyomatosis pulmonary samples, and three sporadic angiomyolipomas. TSC1/TSC2 loss of heterozygosity was previously excluded in these angiomyolipomas. Moderate or strong phospho-ribosomal protein S6 immunoreactivity was found in all lymphangioleiomyomatosis-associated and sporadic angiomyolipomas, suggesting a high incidence of mTOR/p70 S6 kinase signaling pathway activation despite a lack of TSC1/TSC2 loss of heterozygosity. Focally positive phospho-S6 staining was also evident in both lymphangioleiomyomatosis pulmonary samples. We hypothesized that this S6 hyperphosphorylation could reflect mutational activation of Rheb or Rheb-like protein (RhebL1), Ras family members which directly activate mTOR. Mutational analysis performed on DNA from these eight angiomyolipomas plus five additional sporadic angiomyolipomas did not reveal mutations in exons 3 and 4 (homologous sites of Ras activating mutations) of either Rheb or RhebL1. These data suggest that activation of the Rheb/mTOR/p70 S6 kinase pathway is related to the pathogenesis of lymphangioleiomyomatosis-associated and sporadic angiomyolipomas lacking TSC1/TSC2 loss of heterozygosity. This high incidence of mTOR signaling pathway activation suggests that treatment with mTOR inhibitors, such as Rapamycin, may benefit patients with angiomyolipomas independent of the detection of TSC1/TSC2 loss of heterozygosity.

This report deals with 11 examples of renal angiomyolipomas (AML) which appear to include an epithelial element as a part of the neoplasm in the form of gross or microscopic cysts-usually both. There were seven females and four males between the ages of 20 and 70 years with mean age of 45 years. Three of these were known to be symptomatic: intermittent flank pain and gross hematuria for 2 months; recurrent hematuria both before and after flank trauma and a third patient with acute abdomen due to a ruptured tumor blood vessel. Cysts were described in three of the six cases where radiographic data were available. Seven tumors were in the right kidney and four in the left. In gross descriptions, cysts were mentioned in seven and they ranged from 6.0 to 2.0 cm with a median and mean maximal diameter of 5.0 and 4.0 cm, respectively. Microscopically, virtually all of the tumors included multiple smaller cysts and these were lined by flat, cuboidal or columnar epithelium and occasionally hobnail epithelium. There was usually a subepithelial collar of poorly differentiated cells, but the solid element of all tumors was myomatous angiomyolipoma; only one case had any adipose tissue. A dominant histological feature was the prominent lymphatic channels-identical to those of lymphangiomyomas and myomatous or triphasic AMLs. They are much more conspicuous in these cystic cases. Immunohistochemically, all tumors tested were reactive with actin, desmin and HMB-45, with the latter being more intensely positive in the subepithelial collars. Estrogen and progesterone receptors were usually positive, also. The behavior of these lesions appears to be no different from that of other AMLs.

Angiomyolipoma (AML) is a rare benign tumor that occurs most commonly in the kidney. Occasionally it may be found in the liver. Lesions in the liver are usually solitary. Multiple AMLs are extremely rare and are typically seen in patients with tuberous sclerosis. We now report an unusual case of a 46-year-old woman with multiple hepatic AMLs. There were more than 15 lesions distributed predominantly in the right hepatic lobe. The tumors ranged from 0.2 to 6 cm in size and consisted of a variable admixture of proliferating blood vessels, adipose tissue, and smooth muscle. There was no clinical evidence of tuberous sclerosis in this patient. Polymerase chain reaction amplification of the highly polymorphic human androgen receptor gene (HUMARA) was performed and the pattern of X chromosome inactivation was analyzed. Three of the five representative AML nodules showed a preferential loss of one of the two HUMARA alleles indicating a clonal proliferation with involvement of different alleles. Histologic examination of the corresponding lesions showed clonal lesions to be predominantly composed of epithelioid myoid cells while the polyclonal lesions were predominantly composed of adipose tissue. While the histologic diagnosis of AML in a surgical resection specimen is often straightforward, the radiographic, cytologic and intra-operative interpretation of a case with multiple lesions presents a considerable challenge.

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

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by seizures, mental retardation, and hamartomatous tumors in multiple organs, including subependymal giant cell astrocytomas, cardiac rhabdomyomas, and renal angiomyolipomas. Mutations in two genes are associated with TSC: TSC1, which was cloned in 1997, and TSC2, which was cloned in 1993. We report here the expression of hamartin, the product of the TSC1 gene, in normal human tissues and in renal angiomyolipomas from TSC1- and TSC2-linked patients. By Western blot analysis, hamartin is strongly expressed in brain, kidney, and heart, all of which are frequently affected in TSC. By immunohistochemical analysis, the expression pattern of hamartin in normal human tissues was almost identical to that of tuberin, the product of the TSC2 gene. This is consistent with the recent finding that tuberin and hamartin interact and with the clinical similarity between TSC1- and TSC2-linked disease. Strong hamartin expression was seen in cortical neurons, renal tubular epithelial cells, pancreatic islet cells, bronchial epithelial cells, and pulmonary macrophages. Hamartin was also expressed in endocrine tissues, including islet cells of the pancreas, follicular cells of the thyroid, and the zona reticularis of the adrenal cortex. In eight angiomyolipomas from a TSC1-linked patient, no hamartin expression was detected, whereas tuberin, the product of the TSC2 gene, was expressed. In 19 angiomyolipomas from a TSC2-linked patient, in whose angiomyolipomas loss of tuberin expression had previously been shown, hamartin expression was present. These data suggest that tuberin and hamartin immunoreactivity can distinguish tumors with underlying TSC1 mutations from those with TSC2 mutations. This differentiation might have diagnostic implications.

Angiomyolipomas can occur sporadically or in association with tuberous sclerosis complex (TSC). TSC is an autosomal dominant disorder characterized by seizures, mental retardation, and benign tumors of the brain, heart, kidney, and skin. Angiomyolipomas are more common in women than in men, suggesting a possible hormonal influence on tumor growth. In this study, 35 angiomyolipomas from 23 patients were immunostained with antibodies to estrogen receptor (ER) and progesterone receptor (PR). Eleven angiomyolipomas (31%) contained clusters of PR-immunoreactive smooth muscle cells. None contained ER-immunoreactive cells. Of the 21 tumors from patients with TSC, 11 (48%) were PR immunoreactive. All of the PR-immunoreactive angiomyolipomas were from women younger than 50 years of age, and all except one of these women had TSC. This study suggests that hormonal factors play a role in the pathogenesis of TSC-associated angiomyolipomas.