Extramammary Paget's disease (EMPD) typically presents as an eczematous, eroded or crusted plaque. Only a few cases with depigmentation have been reported. We herein report a patient with a depigmented scrotal patch as the sole finding of EMPD. Since he had concurrent rectal cancer, we stained the tissue with gross cystic disease fluid protein-15 (GCDFP-15) and cytokeratin 20 (CK20) in order to differentiate primary/secondary EMPD. This case represents coincidental primary EMPD and rectal cancer, of which the initial features of EMPD were unusual.