Answer: D - BRAF (V600E) mutation 

Histologic sections show fragments of well differentiated non-keratinizing squamous epithelium surrounding central fibrovascular cores (Figs A-C). No stellate reticulum or wet keratin is seen. Such a papillary squamous proliferation in the sellar/suprasellar region is consistent with a "Papillary craniopharyngioma, CNS WHO Grade 1." The vast majority of these neoplasms harbor BRAF (p.V600E) mutations, which can be demonstrated with a mutation specific immunostain (Fig D). 

Craniopharyngiomas are benign tumors of the sellar region that are thought to arise from cellular elements of Rathke's pouch. Both types of craniopharyngioma, adamantinomatous craniopharyngioma (AC) and papillary craniopharyngioma (PC), feature squamous type epithelium. Unlike PCs, ACs are also characterized by stellate reticulum, wet keratin,  occasional islands of squamous whorls, and pronounced basal cell palisading. ACs are driven by beta-catenin mutations, in contrast to the BRAF mutations seen in PC.  Interestingly, PCs may have occasional goblet cells within the squamous epithelium, and rarely demonstrate regions of ciliated epithelium  (fig E). These findings can resemble a Rathke cleft cyst with extensive squamous metaplasia, with some authors suggesting that at least some PCs represent neoplastic transformation of Rathke cleft cysts. 

As craniopharyngiomas are benign lesions,  they would not be expected to harbor a TP53 mutation. BRAF-KIAA1549 fusions are classically associated with pilocytic astrocytomas.