Highly variable clinical feature and course of aggressive digital papillary adenocarcinoma.

Aggressive digital papillary adenocarcinoma (ADPA) is a rare cutaneous tumor with sweat gland differentiation. Due to the high risk of local recurrence and delayed metastasis, the wide local resection of the primary lesion and long-term follow up are recommended for ADPA. Here, we report two cases of ADPA. Case 1 had a blue-gray nodule on the tip of the right middle finger. Case 2 had had a papule on the dorsal side of the left ring finger for 13 years. In both cases, papillary proliferations of the tumor cells showed multilobular adenomatous structures with back-to-back patterns characteristic of ADPA. We amputated the finger at the proximal interphalangeal joint and performed a wide resection of the primary tumor in Case 1 and 2, respectively. Sentinel lymph node biopsy in the axilla was performed, and no sentinel lymph node metastasis was found in either case. Among the previously reported ADPA cases, clinically, most lesions were skin-colored or tan-brown to gray. The blue-gray color in Case 1 is thought to be extraordinary for ADPA. In Case 2, the patient had had the small lesion for more than 13 years and the tumor size had been stable during that long period. The present two cases suggest that ADPA shows a prominent variety of both clinical features and disease courses, and that we cannot exclude the possibility of ADPA even in cases of blue-gray nodules or small, stable, non-progressive papules.