RESUMEN
Cutaneous syncytial myoepithelioma (CSM) is a recently recognized, histopathological variant of myoepithelial (ME) tumors of the skin. It is characterized by a syncytial arrangement of spindled, ovoid, and/or epithelioid cells forming a well-circumscribed, unencapsulated dermal nodule. There is a paucity of intervening stroma, and absent duct or gland formation. Strong immunohistochemical staining for S100 and epithelial membrane antigen (EMA) has been described, while cytokeratin expression has been uncommon. The majority of CSMs harbor a rearrangement involving the EWSR1 gene. Although various fusion partner genes have been discovered in ME tumors at other anatomic sites, none has yet been described in CSM. We present a case of CSM represented clinically by a papule on the mid-upper back of a healthy 44-year-old female. It exhibited morphological and immunohistochemical features of a CSM with strong, diffuse S100 and alpha-actin expression, and focal positivity for EMA and cytokeratin AE1/AE3. Fluorescence in-situ hybridization showed an EWSR1 gene rearrangement. Massively parallel next-generation RNA sequencing revealed PBX3 as the fusion partner. The EWSR1-PBX3 gene fusion has been previously identified in three cases of ME tumors of bone and soft tissue, and in a case of retroperitoneal leiomyoma. This is the first report of an EWSR1-PBX3 fusion in CSM.
Asunto(s)
Biomarcadores de Tumor , Proteínas de Homeodominio , Mioepitelioma , Proteínas de Fusión Oncogénica , Proteínas Proto-Oncogénicas , Proteína EWS de Unión a ARN , Neoplasias Cutáneas , Adulto , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Femenino , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Humanos , Queratinas/genética , Queratinas/metabolismo , Mioepitelioma/genética , Mioepitelioma/metabolismo , Mioepitelioma/patología , Fusión de Oncogenes , Proteínas de Fusión Oncogénica/genética , Proteínas de Fusión Oncogénica/metabolismo , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas/metabolismo , Proteína EWS de Unión a ARN/genética , Proteína EWS de Unión a ARN/metabolismo , Neoplasias Cutáneas/genética , Neoplasias Cutáneas/metabolismo , Neoplasias Cutáneas/patologíaRESUMEN
BACKGROUND: multinucleate cell angiohistiocytoma is a rare benign fibrohistiocytic and vascular proliferation, typically characterized by the development of solitary papules, in an acral distribution in otherwise healthy late middle-aged to elderly women. OBJECTIVE: our objectives are to present a novel case of generalized multinucleate cell angiohistiocytoma and to review the current literature regarding the clinical and histologic findings in this condition, as well as its potential causes and treatments. OBSERVATIONS: we describe a 35-year-old man who presented with generalized asymptomatic firm violaceous papules. Histopathology revealed dermal vascular proliferation; a perivascular infiltrate of lymphocytes, histiocytes, neutrophils, and plasma cells; thickened surrounding collagen bundles; and characteristic multinucleate cells with scalloped borders. CONCLUSION: our patient is one of three patients reported to date with generalized lesions of multinucleate cell angiohistiocytoma who were all in a younger age group (20-40 years old) than previously reported for solitary lesions.