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The authors report six further cases of a cutaneous lymphoid proliferation that share many of the features of a case series previously described as indolent CD8-positive lymphoid proliferation of the ear. Previous reports of this entity have described the slow growth of cutaneous papules and nodules, with a predilection for the ear, associated with specific histopathologic and immunophenotypic features and a benign clinical course. These include the presence of a clear Grenz zone without epidermotropism, and a CD8+ granzyme B- immunophenotype with a low proliferative index. The current case series presents some atypical clinical features, including site of disease beyond the ear and recurrent disease. Despite this, indolent clinical evolution is apparent. Histopathologically, three of the six cases showed a moderate-high proliferative index, while two cases had very focal epidermotropism and Pautrier collections. A single example had significant granzyme B expression. These previously unreported features add to our understanding of this rare entity, which is not currently recognized in the World Health Organization ( WHO)/European Organization for Research and Treatment of Cancer ( EORTC) classification. [ABSTRACT FROM AUTHOR]

Mutations inβ-catenin are present in benign pilomatrixomas.β-catenin is a downstream effector in the WNT-signalling pathway, acting as a signal for differentiation and proliferation. Mutations inCTNNB1, the gene encodingβ-catenin, are present in a wide variety of benign and malignant neoplasms. We examinedβ-catenin in a series of pilomatrix carcinomas (15 cases) by using immunohistochemistry and DNA sequencing of exon 3 fromCTNNB1, and compared these to a series of benign pilomatrixomas (13 cases). All 11 pilomatrix carcinomas available for examination showed nuclear localization ofβ-catenin and mutations in exon 3 similar to those demonstrated in benign pilomatrixomas. Two of 11 pilomatrix carcinomas showed significant nuclear accumulation of p53, whereas this was absent in all 13 benign pilomatrixomas. Expression of nuclear cyclin D1 was similar in both benign pilomatrixomas and pilomatrix carcinomas. Clinical follow-up from the 15 malignant cases reported in this study and by others indicates that wide excision offers superior control of local recurrence, compared to simple excision. Immunohistochemical and molecular analysis ofβ-catenin reveals that both pilomatrix carcinomas and benign pilomatrixomas harbour mutations inβ-catenin. This implies a common initial pathogenesis and is compatible with the proposition that pilomatrix carcinomas may at least on occasion arise from their benign counterparts.Lazar AJF, Calonje E, Grayson W, Dei Tos AP, Mihm Jr MC, Redston M, McKee PH. Pilomatrix carcinomas contain mutations inCTNNB1, the gene encodingβ-catenin. [ABSTRACT FROM AUTHOR]