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Background: Spindle cell carcinoma (SpCC) is a rare microscopic type of cancer of the mouth and oropharynx. Although SpCC is thought to arise from squamous cell carcinoma (SCC), it carries a worse prognosis. Aim: To find out the difference in immunohistochemical expression of cytokeratin, vimentin and smoothmuscle actin, and mutational alterations in the K-ras oncogene between the two tumours, in an attempt to characterise SpCC. Methods: Immunohistochemical analysis was performed by standard avidin-biotin complex method in 35 cases each of SpCCs and SCCs. DNA extracted from paraffin wax-embedded tumours was used for PCR followed by single-strand conformation polymorphism for mutational analysis of K-ras exon 1 and exon 2. Results: In the SpCC group, cytokeratin positivity was significantly higher in epithelial areas (52.2%) than in spindle cell areas (16.1%), whereas vimentin was more positive in spindle cell areas (18.7%) than epithelial areas (2.7%). Cells intermediate between epithelial and spindle cell areas were consistently positive for both cytokeratin and vimentin. Cytokeratin was found to be significantly more positive in SCC (72.6%) than the squamous component and spindle cell component of SpCC. In this study, no mutation was detected in the Kras gene of either the SpCC or SCC group. Conclusions: The spindle cell component of SpCC is intermixed with cells that are morphologically mesenchymal but express dual antigen-positivity characteristic of epithelial (cytokeratin) and mesenchymal (vimentin) cells. These, possibly, are cells in transition suggesting that SpCC may be a sarcomatous metaplasia of SCC.

Crescentic glomerulonephritis remains one of the main causes of acute renal failure with histological diagnosis. Immunohistologic examination is essential for accurate classification into one of the three categories. This condition should be considered in rare causal associations like leprosy or MPGN with renal failure, to allow for timely performed renal biopsy and appropriate aggressive therapy.