A rippled-pattern trichoblastoma: an immunohistochemical study.

Background: Since the first description by Hashimoto et al., there have been only a few case reports of rippled-pattern tricogenic tumor. In addition, there are no reports on detailed immunohistochemical analyses of this rare neoplasm. We describe here an additional case of rippled-pattern trichogenic tumor with a special reference to its immunohistochemical features.
Methods: A nodule arising on the occipital area of a 62-year-old Japanese woman was histologically and immunohistochemically investigated.
Results: Histopathologically, the lesion contained various-sized lobular nests, which consisted of oval to elliptical shaped basaloid cells without any atypia and were embedded in the collagenous stroma. Some elongated basaloid cells were arranged in a palisading fashion forming parallel rows of epithelial ribbons in a rippled-pattern. Cytokeratin (CK) immunohistochemistry showed constant expressions of CK1/5/ 10/14, CK5/8, CK14 and CK7, and focal expressions of CK17 and CK19 in the basaloid cells, suggesting a keratin phenotypical similarity to the cells in small nodular type trichoblastoma.
Conclusions: The present tumor is a variant of trichoblastoma, and considered to be in close association with the outer root sheath and/ or follicular germinative cells.