Cutaneous T cell lymphomas (CTCL) generally have the phenotype of CD3+, CD4+, CD45RO+ memory T cells. CTCL expressing a CD8+ T cell phenotype are extremely rare and ill-defined. To elucidate whether these CD8+ CTCL represent a distinct disease entity, the clinical, histological, and immunophenotypical features of 17 CD8+ CTCL were reviewed. None of the 17 cases expressed markers characteristic of natural killer cells or gamma/delta T cells. Nine of 17 cases showed the characteristic clinical and histological features as well as clinical behavior of well defined types of CTCL, such as mycosis fungoides (2 cases), pagetoid reticulosis (2 cases), lymphomatoid papulosis (2 cases), and CD30+ large T cell lymphoma (2 cases), all of which usually express a CD4+ T cell phenotype, and 1 case of subcutaneous panniculitis-like T cell lymphoma. The other 8 cases formed a homogeneous group showing a distinctive set of clinicopathological and immunophenotypical features, not consistent with that of other well defined types of CTCL. Clinical characteristics included presentation with generalized patches, plaques, papulonodules, and tumors mimicking disseminated pagetoid reticulosis; metastatic spread to unusual sites, such as the lung, testis, central nervous system, and oral cavity, but not to the lymph nodes; and an aggressive course (median survival, 32 months). Histologically, these lymphomas were characterized by band-like infiltrates consisting of pleomorphic T cells or immunoblasts, showing a diffuse infiltration of an acanthotic epidermis with variable degrees of spongiosis, intraepidermal blistering, and necrosis. The neoplastic cells showed a high Ki-67 proliferation index and expression of CD3, CD8, CD7, CD45RA, betaF1, and TIA-1 markers, whereas CD2 and CD5 were frequently lost. Expression of TIA-1 pointed out that these lymphomas are derived from a cytotoxic T cell subset. The results of this and other studies reviewed herein suggest that these strongly epidermotropic primary cutaneous CD8+ cytotoxic T cell lymphomas represent a distinct type of CTCL with an aggressive clinical behavior.

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Among the members of the three families with MEN 2A and RET 634 mutation, the incidence of CLA was 36%, a figure similar to that reported in the literature for phaeochromocytoma (30-50%) and even higher than that for hyperparathyroidism (10-20%). The present data confirm that CLA is linked to codon 634 RET mutations and is a precocious marker of the disorder.

Lichen striatus (LS) is an uncommon dermatosis that generally affects children. The histopathology of LS often shows a polymorphic epidermal reaction process of variable lichenoid and spongiotic changes having no specific histopathological criteria or simulating other diseases. In the present study, we have evaluated the histopathological features of 41 biopsy specimens and the immunohistochemical aspects of 10 cases of LS. In 50% of the cases, we found histopathological and immunopathological features constantly present and allowing a correct diagnosis. In 9 cases, the histopathology was not specific, and in 10 cases, a clear differentiation from other diseases was not possible. Immunohistochemical study demonstrated a CD3+ T-lymphocytic infiltration in which CD8+ cells surrounded necrotic keratinocytes and intraepidermal vesicles filled with Langerhans cells. These findings seem to corroborate the hypothesis that a somatic mutation of a keratinocytic clone could induce an autoimmune response of the host.