Panfollicular carcinoma or trichoblastic carcinoma with panfollicular differentiation?

Herein, we report two cases of a follicular neoplasm with panfollicular differentiation showing architectural and cytologic findings suggestive of a malignancy. Immunohistochemical analysis of β-catenin expression in the neoplasm showed nuclear and cytoplasmic immunoreactivity, with no reactivity in the transitional and shadow cells, consistent with β-catenin expression of pilomatrical tumors. Staining for BerEp4 was positive at the periphery of both neoplasms, suggesting germinative differentiation of the neoplastic cells, whereas staining for the follicular stem-cell marker PHLDA-1 (TDAG51) showed strong focal expression in the tumor cells of both cases. Given these findings, these neoplasms show features of both panfollicular neoplasms and basal cell carcinoma with panfollicular/matrical differentiation. These are the first cases of this neoplasm reported to date. More reports are needed to assess their malignant potential.