Clear cell basal cell carcinoma with sialomucin deposition

Clear cell basal cell carcinoma (BCC) is a variant of BCC with a characteristic clear cell component that may occupy all or part of the tumor islands. Periodic acid-Schiff (PAS) staining for glycogen is variably positive, and mild deposition of sulfated mucin has been noted. However, to our knowledge, clear cell BCC with sialomucin deposition has not been reported. Here we report a case of clear cell BCC showing sialomucin deposition. The clear tumor cells stained with PAS and showed incomplete diastase-resistance. In addition, mucin staining with alcian blue was positive at pH 2.5 but not at pH 0.5.