Can someone who is never speaking of himself and present himself as very altruistic be egocentric / narcissistic? I've tried to make some searches on egocentrism and its opposite (Allocentrism).

The definitions from Wikipedia are: 


  Egocentrism is the inability to differentiate between self and other.
  More specifically, it is the inability to untangle subjective schemas
  from objective reality; an inability to understand or assume any
  perspective other than their own.
  
  Although egocentrism and narcissism appear similar, they are not the
  same. A person who is egocentric believes they are the center of
  attention, like a narcissist, but does not receive gratification by
  one's own admiration. An egotist is a person whose ego is greatly
  influenced by the approval of others while a narcissist is not.
  
  Allocentrism is a collectivistic personality attribute whereby people
  center their attention and actions on other people rather than
  themselves.


But since the prosocial actions are often motivated by ego needs (see Polatch effect for the extreme) can we say that among extreme idealistic people (i.e. militants in extreme organizations) we can find Narcissists as well? 

A narcissist has absence of self-compassion, he thinks to be perfect. Is there a correlation between some form of Narcissism and altruism?

EDIT: I found this


  “(The) Israeli zoologist Amotz Zahavi (suggested that) (a)ltruistic
  giving may be an advertisement of dominance and superiority.
  Anthropologists know it as the Potlach Effect ...  Only a genuinely
  superior individual can afford to advertise the fact by means of a
  costly gift ... through costly demonstrations of superiority,
  including ostentatious generosity and public spirited risk taking...
  (I)f Zahavi is right ... conspicuous generosity (is) a way of buying
  unfakeably authentic (self-)advertising.”


(any help at improving the question is very welcome)
According to the empathy-altruism hypothesis, in some circumstances, people help because they genuinely care about the welfare of the other person and not because of any other personal goal i.e. avoid distress, social norm, Self-affirmation etc.


  The empathy-altruism hypothesis basically states that
  psychological altruism does exist and is evoked by the empathic desire
  to help someone who is suffering. Feelings of empathic concern are
  contrasted with feelings of personal distress, which compel people to
  reduce their own unpleasant emotions. People with empathic concern
  help others in distress even when exposure to the situation could be
  easily avoided, whereas those lacking in empathic concern avoid
  helping unless it is difficult or impossible to avoid exposure to
  another's suffering.


...


  The social exchange theory states that altruism does not exist unless
  benefits to the helper outweigh the costs. C. Daniel Batson disagrees.
  He holds that people help others in need out of genuine concern for
  the well-being of the other person. The key ingredient to helping is
  "empathic concern". According to his 'empathy-altruism hypothesis', if
  you feel empathy towards another person you will help them, regardless
  of what you can gain from it (1991).


There is a lot of debate about the empathy-altruism hypothesis theory, but I tend to agree with it.