Contextual explanation: Internal cognitive conflict. 
Ego dystonic is best understood as a cognitive phenomenon—specifically, the experience of thoughts, impulses, or behaviours that are in conflict with an individual's internalised beliefs, values, or self-image. This clash creates psychological discomfort because the content feels alien or unacceptable to the person's sense of self.

Themes: Self-concept and internal dissonance. 
Ego dystonic relates to the theme of self-concept, as it highlights the boundaries of what a person accepts as part of their identity. It also embodies the theme of internal dissonance, since the core feature is the tension between one's thoughts or impulses and one's self-perception or values.

Nuance: Contradiction with self-image. 
What distinguishes ego dystonic within its category is the specific nature of the conflict: the thought or impulse is not just unwanted, but actively contradicts the person's self-image or core beliefs. This is different from general cognitive discomfort, as the defining feature is the sense of alienness or opposition to the self.