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Basal cell carcinoma (BCC) is a very common tumor, of which the diagnosis is generally easy. Clinical prediction of histopathological subtype however is however often difficult, i.e. the majority of sclerosing BCCs believed to be morpheaform are in fact trabecular or nodular. There is a subgroup of aggressive BCCs, including trabecular (the most common), morpheaform (rare) and micronodular (very rare) subtypes. Differentiating trichoblastoma from BCC is not always easy, but there are distinctive histopathologic criteria and preferential expression of Berp4 in BCC and PHLDA1 in trichoblastoma that may be of help. The group of trichoblastic tumors comprises giant but benign trichoblastomas and trichoblastic carcinomas at the end of the spectrum (of low or high grade). In case of metastatic BCC, one must rule out trichoblastic carcinoma. Morphologic variants of BCC such as pigmented, clear cell, granular cell BCC or BCC with areas of keratinisation are not of poorer prognosis than the classic types. On the opposite, BCC with sebaceous differentiation (in fact sebaceomas) belong to the spectrum of tumors found in Muir-Torre and must be identified. Basosquamous BCCs should be treated like squamous cell carcinomas as they are more aggressive than the nodular subtype. Cet article fait partie du numéro supplément Prise en charge des carcinomes basocellulaires difficiles à traiter réalisé avec le soutien institutionnel de Sun Pharma.