Is aggressive digital papillary adenocarcinoma really aggressive digital papillary adenocarcinoma?

Is aggressive digital papillary adenocarcinoma (ADPA) really aggressive? Does it only occur at digital location? Does it always have microscopic papillary features? Is it really adenocarcinoma? Let’s us address these questions one by one. Is ADPA aggressive? From the term, namely, aggressive digital papillary adenocarcinoma, one would interpret this as high grade malignant tumor with grim prognosis. Is this the case? Let’s answer this question with historical literature review. In 1979 Helwig from the Armed Force Institute of Pathology introduced a term called aggressive digital papillary adenoma and presented 22 cases under this term at the American Academy of Clinical and Pathologic Conference in Chicago [1]. A brief written description of these cases was found as differential diagnosis in an article entitled “eccrine acrospiroma” published in 1984 [2]. Helwig described the so-called aggressive digital papillary adenoma by these words: “I presented 22 examples of aggressive digital papillary adenoma of which 21 occurred on the digits and one on the sole... Microscopically, nests and masses of cuboidal to columnar cells irregularly infiltrate the collagenous stroma. Usually, pleomorphism is minimal. The epithelial patterns vary from solid foci to a more common picture of repeated acinar or glandlike structures fused into larger masses. The gland-like structures have minute or, occasionally, large lumens and often show a papillary configuration. Small foci of squamous differentiation may occur. Thirteen of the 22 tumors recurred at least once, some extended into subjacent bone and, occasionally, amputation of the digit was required. Two tumors metastasized, one to the lung.” [2] As one can see from what was described, these lesions, some of them with recurrences and even metastasis, were not adenomas but carcinomas. For reasons unknown, Helwig did not make straightforward diagnosis of these lesions as carcinoma even in the presence of metastasis, instead he called them “aggressive” adenoma. The term “aggressive” adenoma was used here by Helwig to describe a lesion considered by him as an adenoma but showing recurrences and metastasis. In other word, if this lesion was called carcinoma, then the word “aggressive” would be redundant, since recurrence and metastasis are expected for carcinomas. Decades later when these lesions were called rightly by Duke et al. (also from Armed Force Institute of Pathology) as carcinomas, namely, aggressive digital papillary adenocarcinoma [3], the word “aggressive” was not removed and it remained in the term up to today. With the word “aggressive” remaining in the term, it gives a wrong impression that the lesion under consideration Is aggressive digital papillary adenocarcinoma really aggressive digital papillary adenocarcinoma?