How to identify differentially expressed genes within a single sample group?

[BhariD]

What are the reasonable ways to identify differentially expressed genes within a Single sample group consisting of 5 replicates with RNA-seq data? There is no second or other group to compare.
Appreciate your suggestions. Thank you.

[wdecoster]

Differentially expressed versus what?

[BhariD]

With differentially expressed genes, I meant to say genes that are over-expressed or under-expressed within a single experimental group consisting of more than one replicates. There is no second group or 'normal' group to compare the experimental group. For example, how to identify genes over- or under-expressed in tumor samples of a specific cancer type in the absence of 'normal' samples or any other possible secondary experimental group.

[wdecoster]

But "differentially expressed" implies you compare group A with group B to find differences between the groups.