Psychosis can be considered a cancer of the mind. Psychosis is a class of conditions involving reality distortion due to neuropsychological mechanisms [1]. Cancer is a class of diseases involving uncontrolled cell growth which can potentially invade healthy cells, tissues, and organs [2]. Psychosis is caused by schizophrenia, delusional disorder, bipolar affective disorder, depression with psychosis and other diverse range of disorders. Delusion is a significant manifestation of psychosis and is defined as a fixed belief that is not amenable to change in light of conflicting evidence [3].  According to Sims [4], a delusion is a false, unshakeable belief which is out of keeping with the patient’s educational, cultural, and social background; it is held with extraordinary conviction and subjective certainty. Delusions were described as standing out as exotic specimens in the garden of belief, as examples of what happens precisely when the mechanisms of belief formation break down [5].

Though the underlying etiopathology of delusions is complex, they can be compared to cancerous phenomena in some respects. Cancer is associated with damage to the genetic apparatus of the normal body cells due to a myriad of causes that result in uncontrolled proliferation. This can disrupt the structure and function of other cells, tissues, and organs. Aberrant prediction error signals, likely due to dopamine dysregulation lead to insignificant events becoming important and form delusions which overtake and disrupt other thoughts [6].

There are multiple genetic and environmental factors involved in the etiology of both cancer and psychosis. In cancer, there is the emergence of mutated cells due to the alteration of genes regulating cell growth and differentiation. The body's immune system, at an early stage, repairs damaged tissues with mutated cells by immune cell proliferation, however, some cancerous cells survive this due to impaired antitumor immunity or other factors [7]. Similarly, our psychological defense mechanisms react to curtail abnormal thoughts but some abnormal thoughts may evade that system which leads to the formation of full-blown delusions causing psychosis.

Diagnosis of cancer is by biopsy and examining the tissue to look for abnormal cells or other abnormal patterns e.g. on radiological investigation. Diagnosis of delusion is also by a detailed interview of the patient, distinguishing abnormal beliefs from normal for that person with his sociocultural norms.

Cancer staging involves determining the extent of cancer and involves consideration of factors like tumor size, location, and spread to other systems in the body [8]. Staging is very helpful in determining the treatment plan and prognosis. A staging system has also been proposed for schizophrenia, one of the main causes of psychosis based on the characteristics of symptoms and their severity and chronicity. Staging can assist in determining treatment strategies and prognosis [9].

Management of cancer is a high-priority scenario with the UK guidance that a patient is seen within two weeks of referral for suspected cancer [10]. Management of psychosis is also a high-priority scenario with suggested two weeks guidance [11]. Treatment of cancer is done using a range of different approaches e.g. surgery, radiotherapy, and chemotherapy and can lead to significant side effects [12]. Treatment of delusion involves adopting biological, psychological, and social approaches tailored to the patient and antipsychotic medications can lead to significant side effects.

The prognosis of cancer is generally unfavorable, especially if not diagnosed and treated early. It is one of the leading causes of morbidity and mortality depending on the type of cancer and the systems that it affects. Similarly, the prognosis of disorders with delusion is considered unfavorable and carries morbidity and mortality including significant distress, breakdown of social relationships, impaired occupational functioning, aggression or death by suicide. Factors like the type of an underlying psychotic syndrome like schizophrenia or acute and transient psychosis and the duration of untreated psychosis can affect prognosis [13].

However, no doubt, there are significant differences between cancer and delusion. Whilst cancer is a disease, delusion is a symptom and sign of a wider disorder, though it can be the predominant disorder in some instances, e.g Delusional Disorder. Unlike cancer, delusions can't be physically observed.

In conclusion, it is vital to understand the true nature of psychosis to advance our knowledge of effective management. The comparison of psychosis to cancer offers a potential new avenue to explore its nature and offer new strategies of management. This opens a new avenue of research and underscores the importance of parity of esteem among mental and physical health conditions.

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