Differentiation of Oncocytoma From Chromophobe RCC
Differentiation of Oncocytoma From Chromophobe RCC
RO was first described by Zippel in 1942 as a neoplasm entirely composed of large eosinophilic cells called oncocytes. Later, in 1976, Klein and Valensi identified another 13 cases as a distinct clinical pathological entity with a typical benign histological presentation and clinical course. RO was originally thought to derive from renal proximal tubules, but most pathologists now suggest a distal origin, most likely arising from intercalated cells of collecting ducts. The first description of chRCCs, as distinct from ccRCCs, was made by Theones et al in 1985, and a year later, they added the chRCC subtype to the classification of renal tumours. The cell characteristic had been described prior to the 1985 publication but only in experimentally induced adenomas in animals. The chromophobe cells had slightly opaque or finely reticular cytoplasm that resisted staining with haematoxylin and eosin. They were able to be distinguished from ccRCCs by a strongly positive reaction within their cytoplasm to Hale's colloidal iron, and a weaker positive reaction with Alcian Blue, a distinction that has since been found to be unreliable. The authors, however, made a step forward for classification of RCCs by suggesting that the descriptive term 'light cell' RCC should be discarded and replaced by either 'clear cell' or 'chromophobe cell' as appropriate. They pointed out that chromophobe cell tumours were likely to have a different derivation from ccRCCs and other RCCs, and that they may also have a different prognosis, a fact that has since been established. Since the description of chRCCs came a decade later than ROs, there were many instances in that era where renal tumours, which were likely to be chRCCs, were described as ROs. This may have contributed to the confusion surrounding the original recognition of the benign nature of ROs.
History
RO was first described by Zippel in 1942 as a neoplasm entirely composed of large eosinophilic cells called oncocytes. Later, in 1976, Klein and Valensi identified another 13 cases as a distinct clinical pathological entity with a typical benign histological presentation and clinical course. RO was originally thought to derive from renal proximal tubules, but most pathologists now suggest a distal origin, most likely arising from intercalated cells of collecting ducts. The first description of chRCCs, as distinct from ccRCCs, was made by Theones et al in 1985, and a year later, they added the chRCC subtype to the classification of renal tumours. The cell characteristic had been described prior to the 1985 publication but only in experimentally induced adenomas in animals. The chromophobe cells had slightly opaque or finely reticular cytoplasm that resisted staining with haematoxylin and eosin. They were able to be distinguished from ccRCCs by a strongly positive reaction within their cytoplasm to Hale's colloidal iron, and a weaker positive reaction with Alcian Blue, a distinction that has since been found to be unreliable. The authors, however, made a step forward for classification of RCCs by suggesting that the descriptive term 'light cell' RCC should be discarded and replaced by either 'clear cell' or 'chromophobe cell' as appropriate. They pointed out that chromophobe cell tumours were likely to have a different derivation from ccRCCs and other RCCs, and that they may also have a different prognosis, a fact that has since been established. Since the description of chRCCs came a decade later than ROs, there were many instances in that era where renal tumours, which were likely to be chRCCs, were described as ROs. This may have contributed to the confusion surrounding the original recognition of the benign nature of ROs.
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