The presence of round and annular red patches and plaques and atypical lymphocytes is suggestive of a diagnosis of parapsoriasis en plaque. However, no epidermal involvement was apparent. These findings are typical of the interstitial variant of mycosis fungoides reviewed by Su LD, et al in J Cutan Pathol 2002;29:135-41. Their patients presented with red macules, ill defined red plaques with minimal scale, and nodules on the trunk and proximal extremities. All patients had an interstitial dermal infiltrate of lymphocytes with rare histiocytes resembling the infiltrate seen in the interstitial form of granuloma annulare and inflammatory morphea. In all cases focal collections of epidermotropic lymphocytes were found , and clonal T-cell populations were detected by polymerase chain reaction T-cell gamma gene rearrangement analysis in 2 of 5 cases.
The epidermis is normal. In the dermis there is a perivascular and interstitial infiltrate of lymphocytes some of which appear atypical.