Cytokeratin expression in trichoblastic fibroma (small nodular type trichoblastoma), trichoepithelioma and basal cell carcinoma

Abstract

Classical trichoblastic fibroma or small nodular type trichoblastoma (Ackerman) is a rare tumour. This tumour, trichoepithelioma and basal cell carcinoma (BCC) have some overlapping histopathological features. There are only a few reports on immunohistochemical studies in large series of these three neoplasms. We investigated immunostaining patterns of 10 different anticytokeratin (CK) antibodies and several other markers in these neoplasms, comparing them with the patterns in normal adult and fetal skin. In trichoblastic fibroma (three cases), CK1/5/10/14, CK7, CK8/18, CK10/11, CK14, CK17 and CK19 were expressed in the basaloid nests, and CK6 and involucrin were detected in the inner layers of keratinous cysts. Trichoepithelioma (seven cases) expressed CK1/5/10/14, CK8/18, CK14, CK17 and CK19 in the basaloid nests, and CK6, CK10, CK10/11 and involucrin were positive in the keratinous cysts. However, no CK7 expression was observed. Solid and keratotic types of BCC (29 cases) expressed CK1/5/10/14, CK7, CK8/18, CK14, CK17 and CK19 in the basaloid nests. The keratinous cysts in BCC were stained with anti-CK6, CK10, CK10/11 and involucrin antibodies. Coupled with the expression of CK8/18, CK17 and CK19 in the outer root sheath of the adult hair follicle, these three neoplasms shared a keratin phenotype characteristic of the outer root sheath. Judging from our immunohistochemical results, trichoblastic fibroma and BCC cannot be differentiated by their patterns of CK expression. The expression of CK7, which is noted in fetal hair follicles, trichoblastic fibroma and BCC, suggests the presence of subpopulations that retain fetal phenotypic characteristics in these two neoplasms. Although the current concept regards trichoepithelioma and trichoblastic fibroma as a single tumour group, the lack of CK7 expression in trichoepithelioma supports the notion that the two are different.

Diagnostic utility of immunohistochemistry in distinguishing trichoepithelioma and basal cell carcinoma: evaluation using tissue microarray samples

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15] With exception of D2-40 labeling, 14 the studies present conflicting findings when comparing results for the same immunohistochemical markers. This may be due to the small number of basaloid tumors that comprised their casuistics.…”

“…Other authors built panels with epithelial markers or the association of epithelial and stromal markers. 11,12,16 In this work, the more effective panel was built using data obtained from a linear regression analysis and was composed of at least one marker displaying stromal labeling.…”

Histologic Mimics of Basal Cell Carcinoma

“…4,14 Reports have been mixed regarding CK7 expression in BCC. 14,15 Ber-EP4 typically shows strong expression. 4 There is diffuse nuclear expression of p63.…”

Histopathological Characteristics may not be Useful in the Differential Diagnosis Between Basal Cell Carcinoma and Benign Tumors of Cutaneous Appandages Originating from Hair Follicle

“…10 Trichoepithelioma (TE) is a benign, cutaneous mesenchymal tumor originating from germ layer of hair follicle. [11][12][13] Trichoblastoma (TB) is extremely rare benign tumors located deep dermis and subcutis. 14 It is frequently seen on head and neck 3,15 and mostly sized less than 1 cm in diameter.…”