Storiform Collagenomas With Unusual Morphology: Expanding the Histologic Spectrum in Two Molecularly Proven Cases.

Storiform collagenoma is a rare benign dermal neoplasm recently shown to harbor concurrent PTEN and PDGFRB mutations. While most are sporadic, a subset occurs in the context of Cowden syndrome. We describe two storiform collagenomas with unusual morphology including infiltrative growth pattern and perivascular myoid differentiation. Confirmation of concurrent PTEN and PDGFRB mutations in both cases allowed for a more confident diagnosis of storiform collagenoma in these cases and their distinction from dermatofibrosarcoma protuberans.