The Diagnosis: Epidermotropic CD8+ T-Cell Lymphoma
Epidermotropic CD8+ T-cell lymphoma is a rare aggressive form of cutaneous T-cell lymphoma (CTCL), accounting for less than 1% of all cases.1 Since this subtype of CTCL was first described in 1999 by Berti et al,2 approximately 45 cases have been reported in the literature.1 It typically is found in elderly men and presents as disseminated or localized papules, patches, plaques, nodules, and tumors, often with central necrosis, ulceration, crusting, and hemorrhage (Figure 1).1,3 These lesions rapidly progress and can affect any skin site, but acral accentuation and mucosal involvement are common.4 Due to the rapidly progressive nature of this disease, patients typically present with widespread plaque- and tumor-stage disease.3 Frequency of systemic spread is high, with metastasis to the central nervous system, lungs, and testes being most common. Lymph nodes typically are spared, helping to differentiate this form of CTCL from classic mycosis fungoides.
Figure 1. Background erythema of the chest with overlying ulcerated nodules.
Diagnosis of epidermotropic CD8+ T-cell lymphoma is based on a combination of clinical, histopathologic, and immunohistochemical features. Histopathologic components include epidermotropism, particularly in the basal cell layer, in a pagetoid or linear pattern. A second feature is a dermal infiltrate consisting of a nodular or diffuse pattern of atypical lymphocytes that extend to the subcutaneous fat (Figure 2). All cases of epidermotropic CD8+ T-cell lymphoma express the CD8+ phenotype and most have a high Ki-67 proliferation index and are CD3, CD45RA, and/or T-cell intracellular antigen 1 positive.1
Figure 2. Diffuse dense dermal infiltrate of lymphocytes filling the entire dermis (H&E, original magnification ×40).
Due to its aggressive nature, epidermotropic CD8+ T-cell lymphoma has a poor prognosis, with an average 5-year survival rate of 18% and median survival of 22.5 months.3 Treatment proves difficult as conventional therapies for CD4+ CTCL have proven ineffective for epidermotropic CD8+ T-cell lymphoma. Partial response has been seen with bexarotene alone and with total skin electron beam therapy combined with oral retinoids.1