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Role of POU4F3 in the Diagnosis of Cutaneous Follicular Tumors
Andrew A Gerber1, Gregory A Hosler1,2, Mai P Hoang3
1Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Background:
Detection of keratin 20+ intratumoral Merkel cells can help differentiate benign cutaneous follicular tumors from malignant histopathologic mimics, though interpretive challenges highlight the need for additional diagnostic markers. POU4F3, a sensitive and specific nuclear marker for neoplastic Merkel cells, has yet to be thoroughly investigated as a marker for non-neoplastic Merkel cells within follicular neoplasms.
Methods:
We compared the performance of POU4F3 and keratin 20 in the detection of intratumoral Merkel cells. POU4F3 and keratin 20 immunostains were performed on 78 cases representing benign follicular tumors (trichoblastoma/trichoepithelioma, desmoplastic trichoepithelioma, trichofolliculoma, and basaloid follicular hamartoma), tumors with unclear pathogenesis (fibroepithelioma of Pinkus and cutaneous lymphadenoma), and malignant mimics (microcystic adnexal carcinoma and basal cell carcinoma).
Results:
POU4F3+ intratumoral Merkel cells were detected in all cases of trichofolliculoma, basaloid follicular hamartoma, and fibroepithelioma of Pinkus, and in most cases of trichoblastoma/trichoepithelioma (94%), desmoplastic trichoepithelioma (91%), and cutaneous lymphadenoma (60%). POU4F3+ intratumoral Merkel cells were observed in 22% of microcystic adnexal carcinomas and absent in all basal cell carcinomas. Concordance between POU4F3 and keratin 20 expression was observed in 95% of cases.
Conclusions:
These findings support POU4F3's diagnostic value in distinguishing benign follicular tumors from malignant histopathologic mimics.
