Figure 3.

Histologic variants outside of those in the medulloblastoma, include the classic biphasic variant (A‐D) and the ganglioneuroblastoma variant (E‐L). Classic biphasic tumors are characterized by nodules of differentiation with primitive internodular areas (A). These tumors can be differentiated from desmoplastic/nodular tumors by reticlulin stain (B) which fails to outline the nodules. On the molecular subgrouping stains, classic biphasic tumors fall into the non‐WNT/non‐SHH molecular group based on negativity for YAP1 (C) and GAB1 (D), and staining for beta‐catenin that is restricted to the cytoplasm (not shown). The ganglioneuroblastoma variant is characterized by a mixture of primitive elements mixed with areas ganglion cell differentiation (E‐G). The ganglion cell differentiation is marked by especially high intensity staining for synaptophysin (H) and immunoreactivity for NeuN (I). Tumors showing ganglioneuroblastoma histology typically fall in the non‐WNT/non‐SHH molecular subgroup, showing negative staining for YAP1 (J), negative staining for GAB1 (K), and cytoplasmic only staining for beta‐catenin (L).