BACKGROUND: Trichoblastic fibroma is a benign trichogenic tumor that has both epithelial and mesenchymal components and exhibits partial to complete follicular induction. We studied 10 cases of trichoblastic fibroma and reviewed their clinical and histologic features. OBSERVATIONS: All 10 tumors were located on the face. Nine of 10 patients were women. The mean age at presentation was 63.8 years (range, 35 to 81 years). Two distinct subsets of trichoblastic fibroma were identified: the nodular variant and the plaque variant. The nodular variant is well circumscribed, while the plaque variant is poorly circumscribed, has significant subclinical extension, and may represent the low-grade malignant counterpart of the classic nodular trichoblastic fibroma. Histologically, both variants demonstrate mesenchymal induction with keratin cysts, papillary mesenchymal bodies, and an inductive fibroblastic stroma. CONCLUSIONS: Trichoblastic fibroma may be confused clinically and/or histologically with basal cell carcinoma. Identification of the mixed epithelial-mesenchymal components is helpful in tumor recognition. The plaque variant trichoblastic fibroma has not been previously reported. Familiarity with this variant is important because of the potential for infiltrative growth.
BACKGROUND:Trichoblastic fibroma is a benign trichogenic tumor that has both epithelial and mesenchymal components and exhibits partial to complete follicular induction. We studied 10 cases of trichoblastic fibroma and reviewed their clinical and histologic features. OBSERVATIONS: All 10 tumors were located on the face. Nine of 10 patients were women. The mean age at presentation was 63.8 years (range, 35 to 81 years). Two distinct subsets of trichoblastic fibroma were identified: the nodular variant and the plaque variant. The nodular variant is well circumscribed, while the plaque variant is poorly circumscribed, has significant subclinical extension, and may represent the low-grade malignant counterpart of the classic nodular trichoblastic fibroma. Histologically, both variants demonstrate mesenchymal induction with keratin cysts, papillary mesenchymal bodies, and an inductive fibroblastic stroma. CONCLUSIONS:Trichoblastic fibroma may be confused clinically and/or histologically with basal cell carcinoma. Identification of the mixed epithelial-mesenchymal components is helpful in tumor recognition. The plaque variant trichoblastic fibroma has not been previously reported. Familiarity with this variant is important because of the potential for infiltrative growth.