HMB

Melanocytes have not been described in the pituitary of mammals or in the meninges of the rat. In this paper, we report the presence of the cluster of melanocytes in the intermediate lobe of the pituitary and around the median eminence of the hypothalamus forming an ‘infundibulo-hypophysial circle’, and also describe the characteristics of meningeal melanocytes in Zucker rats. In the leptomeninges, numerous melanocytes were found on the ventrolateral surface of cerebral hemisphere in the area of the middle cerebral artery. Pigment granules were also observed in the surrounding tissue outside the melanocytes as well as incorporated in the cytoplasm of neural and epithelial cells. Electron microscopy revealed that melanosomes in hypophysial and meningeal melanocytes were in different (II-IV) stages of maturity. In the leptomeninges of Zucker rats, HMB-45 immunoreactivity was found in round non-melanosome-containing cells, while no HMB-45 reaction was found in the leptomeninges of the albino rat. We conclude that both obese and lean Zucker rats possess functionally active melanocytes in the meninges and the pituitary and transfer pigment granules to neighboring cells. The distributions of melanocytes in proximity to blood vessels in the leptomeninges and in the ‘infundibulo-hypophysial circle’ suggest an endocrine secretory function.

Renal Angiomyolipoma (AML) is a benign lesion with a variable admixture of fat cells, thick walled blood vessels, smooth muscle and polygonal epithelioid cells. The lesion can be diagnosed with certainty in the presence of all the components on fine needle aspiration, supported by CT findings. However the presence of predominant population of epithelioid cells with paucity or absence of other components can be particularly worrisome, especially if radiological findings are noncontributory. These large cells with low N:C ratio and frothy cytoplasm and anisonucleosis require detailed evaluation and careful search for typical background cytology. Two such cases of AML with a predominant population of epithelioid cells are being described with their cytological and histological findings with a review of literature to highlight the diagnostic dilemma and emphasize the utility of HMB-45 immunostaining in such cases.

Although angiomyolipoma (AML) is a relatively rare entity, it is the most common benign mesenchymal neoplasm of the kidney. To highlight the clinicopathological characteristics of AML and to assess the role of Human Melanoma Black-45 (HMB-45), Melan-A, smooth muscle actin (SMA), S-100 and cytokeratin in its diagnosis. The study included 15 cases of AML. Clinical and radiological data were retrieved from the archival files and all cases were subjected to a histopathological evaluation as well as immunohistochemical staining for HMB-45, Melan-A, SMA, S-100, and cytokeratin. AML was more common in females (female:male = 4:1), the mean age was 53.9 ± 6.45 years. 60% of patients were symptomatic while the remaining 40% were asymptomatic. A statistically significant relationship was found between size of the tumor and the presence of the symptoms (P = 0.02). Patients with tumor size less than 4 cm were asymptomatic, while those with tumor size larger than 4 cm had different symptoms. Thir...