Intradermal Band-like Lipomatous Metaplasia Can Be Associated With the Regression of Overlying Skin Neoplasms: A Clinicopathologic Study of 20 Cases.

Lipomatous metaplasia has been rarely reported in both neoplastic and inflammatory dermatological disorders. Most neoplastic cases show the lipomatous change within the tumor silhouette, but band-like lipomatous metaplasia in the dermis under tumors has not been well-described. The aim of this study was to reveal the characteristics and relationship of intradermal band-like lipomatous metaplasia and coexisting skin tumors. A total of 20 cases with intradermal band-like lipomatous metaplasia were retrieved from 10,992 archive cases between April 1997 and March 2020 at Hyogo Cancer Center, and subjected to a detailed clinicopathologic analysis. Nine (45%) patients had superficial variant basal cell carcinoma as a coexisting neoplasm. Eight (40%) patients had squamous cell carcinoma, 5 of which were in situ. The remaining 3 (15%) cases were invasive extramammary Paget disease. All 20 cases showed at least one of 3 signs of tumor regression, namely, partial loss of overlying neoplasia, significant inflammatory infiltrate under the tumor, and fibrosis around the tumor. We concluded that intradermal band-like lipomatous metaplasia could be seen in association with the regressing process of cutaneous superficially-spreading neoplasms.