Basal cell carcinoma associated with non-neoplastic cutaneous conditions: a comprehensive review.

Basal cell carcinoma (BCC) can be a component of a collision tumor in which the skin cancer is present at the same cutaneous site as either a benign tumor or a malignant neoplasm. However, BCC can also concurrently occur at the same skin location as a non-neoplastic cutaneous condition. These include autoimmune diseases (vitiligo), cutaneous disorders (Darier disease), dermal conditions (granuloma faciale), dermal depositions (amyloid, calcinosis cutis, cutaneous focal mucinosis, osteoma cutis, and tattoo), dermatitis, miscellaneous conditions (rhinophyma, sarcoidal reaction, and varicose veins), scars, surgical sites, systemic diseases (sarcoidosis), systemic infections (leischmaniasis, leprosy and lupus vulgaris), and ulcers. The relationship between the BCC and the coexisting non-neoplastic condition may be coincidental or possibly related to the development of the BCC; alternatively, the development of the BCC may be unrelated to the coexisting non-neoplastic conditions and secondary to either a Koebner isomorphic response or a Wolf isotopic response in an immunocompromised district of skin. This paper reviews several of the case reports and studies that describe the association of BCC with these non-neoplastic cutaneous conditions.