Myoepithelial carcinoma on the right shoulder: Case report with published work review

Myoepithelial carcinoma is a malignant tumor that can differentiate towards myoepithelial cells and commonly occur in the salivary glands. There have been only a few reports of primary cutaneous myoepithelial carcinoma; however, most cases showed subcutaneous involvement and could also be diagnosed as soft tissue myoepithelial carcinoma arising from the subcutis with dermal involvement. It may thus be impossible to distinguish a primary cutaneous from a soft tissue myoepithelial carcinoma. Herein, we describe a case of myoepithelial carcinoma on the shoulder in an 85-year-old Japanese woman. The tumor was located in the whole dermis and subcutis; therefore, it could be diagnosed as either a cutaneous or soft tissue myoepithelial carcinoma. We reviewed previous cases of primary cutaneous and soft tissue myoepithelial carcinomas and compared their clinical and immunohistological features. We found no obvious differences in anatomical distribution or immunohistochemical findings. However, the recurrence rate of cutaneous myoepithelial carcinomas seems to be lower than that of soft tissue carcinomas. Such a difference may be attributable to the adequate surgical margin in cutaneous carcinomas compared with the deep-seated soft tissue carcinomas. The metastatic frequency did not significantly differ between the two types. Although we could summarize from only a small number of cases, these results indicate the difficulty in distinguishing between cutaneous and soft tissue myoepithelial carcinomas; furthermore, it may not be suitable to distinguish them on the basis of aggressive behavior.