Reactive Eccrine Glands Hyperplasia in Vascular Proliferations
We have read with interest the report by Patterson et al1 on the clinicopathologic characteristics of eccrine angiomatous hamartoma.
In their study, the authors described 18 cases of eccrine angiomatous hamartoma. Their figures 3, 4, and 6 are supposedly from a single patient. The histopathology showed proliferated vessels involving the papillary dermis, deep dermis, and subcutaneous tissue. From our viewpoint, the proper diagnosis for the 3 figures should be verrucous hemangioma. In our recent publication,2 we showed that verrucous hemangioma is characterized by proliferation of vessels from papillary dermis into subcutaneous tissue. We also showed prominent eccrine glands proliferation in 4 cases of verrucous hemangioma. Actually, eccrine glands proliferation is not specific for eccrine angiomatous hamartoma. In addition to eccrine angiomatous hamartoma and verrucous hemangioma, we have observed eccrine glands proliferation in other vascular lesions including infantile hemangioma and tufted hemangioma (Fig. 1). We also found one publication that described eccrine angiomatous hamartoma which was actually infantile hemangioma with reactive eccrine glands hyperplasia.3 According to Kazakov et al,4 the proliferative eccrine glands in eccrine angiomatous hamartoma represent reactive hyperplasia of eccrine glands induced by excessive blood supply from abnormal surrounding vessels.
In our recent publication on eccrine angiomatous hamartoma,5 we analyzed 21 cases and performed immunohistochemical studies with lymphatic markers including D2-40 and Prox1, and found that D2-40 was positive or focally positive and Prox1 was positive in endothelial cells of eccrine angiomatous hamartoma. These results suggest that eccrine angiomatous hamartoma is actually a lymphatic malformation with reactive eccrine glands hyperplasia. However, the authors did not perform immunohistochemical evaluation in their work and did not cite our work. We feel that their figure 2 showed dark nodules on the knee that were similar in appearance to a superficial lymphatic malformation and suggested a lymphatic origin of the lesion.
In conclusion, Patterson et al have misdiagnosed verrucous hemangioma with reactive hyperplasia of the eccrine glands as eccrine angiomatous hamartoma. Eccrine angiomatous hamartoma is actually a lymphatic malformation with reactive eccrine glands proliferation. Reactive hyperplasia of eccrine glands is not exclusive to eccrine angiomatous hamartoma and can be observed in other vascular proliferations.