This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Histo Pathology, Subject name: Pathology
For detection of carcinoma lip, stain used is? 
Select and explain. 
A. Giemsa, B. Crystal violet, C. Toulidine blue, D. Hematoxylin and eosin
C: Toulidine blue
Answer: C: Toulidine blue 
Explanation: Ans. (c) Toulidine blue(Ref: Early Diagnosis and Treatment of Cancer Series: Head and Neck Cancers, Wayne Koch Pg. 54)*Toluidine blue stain is used as a marker to differentiate lesions at high risk of progression in order to improve early diagnosis of oropharyngeal carcinomas.*Toluidine blue, an acidophilic metachromatic dye of thiazine group selectively stains acidic tissue components (sulfates, carboxylates and phosphate radicals), thus staining DNA and RNA.