Healed with steel: Myerson’s phenomenon involving a seborrheic keratosis

Summary: Myerson’s phenomenon is eczematous inflammatory reaction pattern that has been described most frequently with melanocytic lesions and sporadically in a variety of other cutaneous lesions including vascular malformations and nevus sebaceus. We present a case of a 71-year-old male who presented to the dermatology clinic with a mildly pruritic well circumscribed erythematous annular plaque with double edged yellow scale on the left lateral thigh. The plaque demonstrated mild central clearing and an eccentric tan crusted papule within the lesion. The differential diagnosis included tinea corporis, erythema migrans, and erythema annulare centrifugum. A shave biopsy was preformed and removed the entire tan papule. On histopathologic review, the sections demonstrated an overall well circumscribed acanthotic epidermal neoplasm with horn cyst formation and no atypia. There were areas of focal serum crust, parakeratosis of the epidermis and diffuse spongiosis which extended beyond the neoplasm to the surrounding epidermis. Patchy dense perivascular lymphohistocytic inflammation was present with scattered eosinophils. The patient was provided a diagnosis of Myerson’s phenomena involving a seborrheic keratosis. Without any additional intervention the lesion showed significant improvement at 3 week follow up and complete resolution at 4 months.