Carcinoma is a cancerous growth. Carcinoma is a skin cancer. Carcinoma occurs in the epithelial tissues. The cells layers are formed by this epithelium tissue. In other words, carcinoma affects those skin tissues that make up the protective inner sheet of all our vital internal organs. However, intensive researches are on to find out the exact clues that can go to prove that these malignant cells can effectively break through the defensive barriers of the cells by breaking the protective epithelium membrane.

The epithelium layer consists of the sentinel cells that not just protect the organs but also do several other vital functions. Among these roles played by the epithelium tissue are transcellular transport, secretion, sensation detection, absorption, and selective permeability.

In most of the unattended cases, carcinoma spreads to other portions of the body like the lymph nodes. Once carcinoma becomes malignant, it is medically termed as carcinoma in situ (CIS). Carcinoma is therefore a tumor that is malignant and invasive as well. Carcinoma is one the four common types of cancers. Carcinoma or for that matter any form of cancer occurs when there is an uninterrupted growth of anomalous (cancerous) cells after they mutate from the normal tissues. The uncontrollable birth of so many irregular cells can be diabolic as they can come in the way of the smooth functioning of the different important organs of the body. Once these mutated cancerous cells spread to other parts of the body they can very well destroy the body's immune system as well.

In many cases, the medical experts identify the tumors via the presumptive organs or cell of origin, viz., putative (also known as the renal cell carcinoma or the hepatocellular carcinoma) or the primary (prostate carcinoma).

According to the histopathology scheme, carcinoma has been classified into Adenocarcinoma and squamous cell carcinoma. In other words, the carcinoma cells can appear as glandular (as in the case of Adenocarcinoma) or squamous. There are then the undifferentiated forms of carcinoma where the tumors are anaplastic and have no fixed or typically identifiable appearances, histologically speaking.

Therefore, carcinoma is divided into five main types. They are adeno, squamous cell, small cell, large undifferentiated cell and Sinonasal. Adenocarcinoma forms structures that are glandular in shape. Adenocarcinoma habitats are the pneumocytes of the type-II category and the goblet cells. Adenocarcinoma takes birth in the epithelial glandular tissue cells. Its primary roosting place is the lung. Such carcinoma are located in the lung in a peripheral manner. Carcinoma of the Squamous cell arises owing to the squamous metaplasia. Such squamous cell carcinoma also lodges in the lung. Smoking leads to the carcinoma of small cell. Such carcinoma cells spread (metastasize) to other parts of the body in the initial stages. They can lower sodium concentration in the patient's body by secreting ADH. The undifferentiated carcinomas of large cells are rather aggressive. They generally attack the lung's central portions. Approximately 18 per cent of the neoplasms in the lung take place due to this type of carcinoma.

The medical experts use a typical system used to measure the level of differentiation of the malignant tumor from the mother tissue. This scale is called the grading system and it tells the metastasize extent of the neoplasm. Prognosis is less whenever the scale denotes minor differentiation. More often than not, the traditional system of Duke's staging classification is also used to diagnose the more common forms of tumors.