Hypothesis: symmetrical cutaneous lymphoma.

Patients with malignant lymphoma may have cutaneous and subcutaneous involvement that exhibits a striking symmetry about the coronal axis. The symmetry of these lesions may be caused by site-specific migration from the circulation, preferential proliferation by lymphocytes of the neoplastic clones at defined anatomical sites, or both mechanisms. Similar behaviour by benign lymphocytes may explain the symmetry and selective anatomical distribution of lesions in other skin diseases.