Erythema multiforme,Stevens–Johnson syndrome and toxic epidermal necrolysis: Frozen‐section diagnosis

Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) may be fatal. Although classified by body surface area skin detachment, initial stages of both may present with erythema multiforme (EM)‐like lesions. To diagnose and predict disease activity adequately as early as possible for patients revealing EM‐like lesions, we performed frozen‐section diagnosis. Thirty‐five patients clinically diagnosed as EM, SJS or TEN were biopsied to diagnose and predict disease progression within the initial‐visit day. Half of a histological section taken from a lesion was snap‐frozen and immediately cryostat‐sectioned, acetone‐fixed and stained with hematoxylin–eosin. Specimens were examined with light microscopy for presence of epidermal necrosis. A section from unaffected sites was also examined for 11 patients. Specimens were examined with light microscopy for presence of graft‐versus‐host reaction (GVHR)‐like findings: apoptotic keratinocytes and satellite cell necrosis. Epidermal necrosis was seen in nine patients. Initial diagnosis of the nine was one of overlap SJS‐TEN, four of SJS and four of EM, and final diagnosis of those was one of TEN, one of overlap SJS–TEN, four of SJS and three of EM. Dissociation between initial and final diagnosis was seen in three cases. GVHR‐like findings in the epidermis were observed in two patients finally diagnosed as overlap SJS–TEN and TEN. Frozen sections are useful not only to make a diagnosis of erythema multiforme but to assess a potential to exhibit more aggressive clinical behaviors (SJS or TEN).