Trichofolliculoma has been shown positive for K15 and K16, suggesting differentiation to the outer root sheath and the hair bulge. 8 The present results strongly support the concept of Kimura et al. 1 that FSCH is distinct from sebaceous trichofolliculoma as it is devoid of prominent differentiation towards the hair follicles. Trichoadenoma has been shown positive for K15 and K17, suggesting differentiation towards the infundibulum and the hair bulge. 9 In trichilemmoma, the tumour was shown to express K15, K16 and K17, suggesting that it differentiates towards the infundibulum, the outer root sheath, the hair bulge and the sebaceous gland. 6 In summary, in FSCH, keratin expression in each of the epithelial components, including the infundibular cystic-like structure, sebaceous duct-like structure and sebaceous celllike structure, was almost identical to that in the normal pilosebaceous unit. Based on the expression of keratin and filaggrin, FSCH differentiates toward the follicular infundibulum, sebaceous duct and sebaceous cells. These findings help to distinguish FSCH from other tumours of hair appendages. Kusumoto K et al. Trichofolliculoma: case report with immunohistochemical study of cytokeratins. Br J Dermatol 2003; 148:597-8. 9 Kurokawa I, Mizutani H, Nishijima S et al. Trichoadenoma: cytokeratin expression suggesting differentiation towards the follicular infundibulum and follicular bulge regions. Br J Dermatol 2005; 153:1084-6.