Contributor: Gordon K. Klintworth
The designation clear cell carcinoma (clear cell tumor) refers to several different tumors that have a clear cytoplasm in hematoxylin and eosin stained tissue sections. The water-clear cytoplasm is due to the presence of abundant intracytoplasmic glycogen, lipid or mucin. Clear cell carcinomas can arise in many parts of the body: kidney (renal cell carcinoma), breast (clear cell breast carcinoma), cervix uteri  (clear cell cervix carcinoma), vagina (clear cell vagina carcinoma), endometrium (endometrium clear cell carcinoma), colon (clear cell colon carcinoma), gall bladder [clear cell tumor - gall bladder], liver [carcinoma - hepatocellular clear cell], gallbladder [carcinoma - gallbladder clear cell],  extrahepatic bile ducts [carcinoma - bile duct clear cell], rectum (clear cell rectum carcinoma), lung (clear cell lung carcinoma), salivary glands (clear cell salivary gland carcinoma), skin (clear cell basal cell carcinoma, clear cell hidradenocarcinoma, clear cell syringoma), thymus (clear cell thymus carcinoma), thyroid gland (clear cell thyroid carcinoma), pancreas [clear cell tumor - pancreas], ovary [carcinoma - ovary clear cell],  jaw (clear cell oncogenic tumor) endocrine system and oral mucosa. In addition other clear cell tumors are the clear cell myoepithelioma, and clear cell oncocytoma). The distinction between these tumors may be difficult and impossible without immunohistochemical stains. Stains with periodic acid-Schiff with and without diastase, mucicarmine, pCEA, EMA, BER-EP4, Kermix, Factor XIII-A, hepatitis B surface antigen, C-reactive protein, and alpha-1 antitrypsin may be helpful in establishing a definitive diagnosis.
The differential diagnosis of a clear cell carcinoma includes several benign (balloon cell nevus, benign "sugar" tumor of the lung, clear cell meningioma) and malignant tumors (clear cell sarcoma , balloon cell melanoma).