In any oral malignancy, is it possible that total leukocytes count is normal and no lymphadenopathy .

Yes: Localized malignancies such as squamous cell may not have systemic manifestations such as lymphadenopathy, especially at early stages.

Yes, possible: Most oral cancers are squamous cell carcinomas. If early stage, there will be no spread to the lymph nodes. Also the total leukocyte count will not be affected.

Two comments: There are several different populations of white bood cells and each give you different clues. Lymphocytes, for instance, tell you about infection. Eosinophils may be a more specific indicator of malignancy. Total white blood cell count may not tell the whole story early on - and if it is early, you may not yet have enough reaction in the local area to cause big lymph nodes to appear.