Melanocytic matricoma is a recently described lesion characterized by well-circumscribed nodules composed of matrical and supramatrical cells with clustered ghost cells, and admixed pigmented dendritic melanocytes, with no cyst formation or connection to the epidermis or pre-existing hair follicles. Although variable cytologic atypia and frequent mitoses in the epithelial component may be present, given the well-defined margins and absence of tumor recurrences, these lesions were initially considered benign neoplasms, and not matrical carcinoma. Theoretically, the detection of numerous melanocytes in matrical carcinoma should not be surprising, but is in fact a very unusual feature. A case with extensive melanization of epithelial elements and only rare melanocytes has been reported. We report two cases of matrical carcinoma with prominent melanocytic hyperplasia, with emphasis on the ultrastructural and immunohistochemical features. Our cases might be considered the malignant counterpart of the so-called melanocytic matricoma.
Basal cell carcinoma (BCC), the most common malignant neoplasm of skin, may show a wide spectrum of histologic appearances. The presence of peripheral palisades is a very characteristic feature of BCC but, to our knowledge, central nuclear palisading has never been described. We report two cases of BCC exhibiting striking central nuclear palisading with Verocaylike bodies, in a pattern reminiscent of schwannoma. Peripheral palisades and clefts were also present in most tumor nodules and lobules, giving the neoplasms the overall configuration of otherwise typical solid BCC. In addition, foci of conventional BCC could be found adjacent, and in transition, to schwannoid areas. The immunohistochemical study showed strong reactivity for keratins (AE1 and AE3) in tumor cells, whereas no immunostaining for S-100 or muscle-specific actin was found. This previously undescribed histological feature of BCC should lead us to include BCC in the list of tumors to be considered in the differential diagnosis of a cutaneous neoplasm with schwannoid features.
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