You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is M.C. site of CA oesophagus is - and explain in detail?
Esophageal Carcinoma is of two common histological types


Squamous cell Ca - the MC type in the world (-95% according to Sabiston)
Adenocarcinoma - where incidence is increasing at a rapid rate and is now the MC type in the USA (Ref:• Harrison, Schwartz)


Distribution of Squamous Cell Ca.

Upper 1/3 → 10%
Middle 1/3 → 60%
Lower 1/3 → 30%     

Adenocarcinoma is mainly located in lower 1/3.
Nowhere, I could get the MC site of esophageal carcinoma overall (including both squamous and adeno variety). 
But one thing is sure - squamous cell Ca is the MC type of esophageal cancer in the world 


So I presume that the overall MC site would be the MC site involved by the MC type of esophageal cancer i.e. → Middle 1/3

So remember
MC type of esophageal Ca in world → Squamous Cell Ca (-95%) MC site → Middle 1/3