Exceedingly rare cases of neoplasms with clear-cut histopathologic features of benignity can show locoregional or even distant spread. Such cases can become putative examples of “benign metastasis” when a completely favorable clinical outcome is documented after an adequately long follow-up. We report 8 cases of morphologically benign clear cell nodular hidradenoma (CCNH) with lymphatic involvement. In 5 cases the cutaneous tumor showed small foci of intravascular deposits of neoplastic cells; in 2 cases the cutaneous tumor presented with a synchronous tumor in a regional node; in 1 case a nodal location CCNH was found with no evidence of any primary in the skin. All the cases were treated with conservative surgery and none of them showed disease progression during a follow-up period ranging from 2 to 11 years. These data suggest that in the absence of other histopathologic features of malignancy, lymphatic spread in CCNH can still carry an excellent prognosis and can be therefore considered as an example of “benign metastasis.” As the latter concept can be set forth only after an uneventful long-term follow-up, in routine practice, cases of morphologically benign CCNH with lymphatic involvement are best labeled “atypical CCNH,” or “CCNH-like tumor of uncertain malignant potential.”
*Department of Dermatopathology, St John’s Institute of Dermatology, St Thomas’s Hospital, London, UK
†Department of Oncology, Anatomic Pathology Unit, Gaetano Rummo General Hospital, Benevento, Italy
‡Department of Histopathology, Institute for Pathology, University of Bern, Bern, Switzerland
§Department of Dermatology, University of Lubeck, Lubeck, Germany
This work was presented in part at the ninth Joint Meeting of the International Society of Dermatopathology, March 1 and 2, 2006, San Francisco, CA.
Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.
Correspondence: Catherine M. Stefanato, MD, FRCPath, Department of Dermatopathology, St John’s Institute of Dermatology, St Thomas’s Hospital, Lambeth Palace Road, SE1 7EH London, UK (e-mail: email@example.com).