Histology reveals a nodular or diffuse proliferation of lymphocytes, usually with marked epidermotropism (Fig. 6.3). In spite of the name of this lymphoma, the epidermotropism may be less pronounced in some lesions, especially in advanced stages (Fig. 6.4). As in all aggressive cutaneous lymphomas, invasion and destruction of adnexal skin structures are common (Fig. 6.5). Cytomorphology is variable and can be characterized by small-, medium- or large-sized pleomorphic cells (Fig. 6.6). Some cases may show a predominance of immunoblasts. Intraepidermal vesiculation and necrosis can be seen. Angiocentricity and angiodestruction are uncommon.
Fig. 6.7 Epidermotropic CD8+ cutaneous T-cell lymphoma. Staining for CD8 highlights the epidermotropic lymphocytes.
Cases of CD8+ T-cell lymphoma with exclusive involvement of the subcutis should be classified as subcutaneous T-cell lymphomas (see Chapter 5).
Distinction of epidermotropic CD8+ cutaneous T-cell lymphomas from cutaneous y/ 8 T-cell lymphomas is difficult and often determined on an arbitrary basis. We prefer to classify those cases with a y/8 phenotype independently as they usually show a more prominent involvement of the subcutaneous fat than cases of epidermotropic CD8+ cutaneous T-cell lymphoma. Another differential feature is the presence of a marked interface dermatitis in many cases of cutaneous y/8 T-cell lymphoma. However, it remains to be determined whether or not these two diseases represent phenotypical variations of the same entity.
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