Cutaneous Myoepithelial Neoplasms on Acral Sites Show Distinctive and Reproducible Histopathologic and Immunohistochemical Features

Abstract

Cutaneous myoepithelial neoplasms are a heterogenous group of neoplasms with mixed tumors typically affecting the head and myoepitheliomas showing a predilection for the extremities. Their malignant counterparts, myoepithelial carcinoma, and malignant mixed tumor are exceptionally rare in the skin, and the morphologic criteria for malignancy are only poorly defined. The aim of the present study was to characterize the clinicopathologic features of myoepithelial neoplasms presenting on acral skin. The clinical and histopathologic features of 11 tumors were recorded, and follow-up was obtained. Immunohistochemistry was performed for S100, SOX10, glial fibrillary acidic protein, keratins, epithelial membrane antigen, p63, p40, smooth muscle actin, desmin, and PLAG1. The tumors mainly affected the feet of adults (range: 26 to 78 y; median: 47 y) with a predilection for the great toe and a male predominance of 1.8:1. Most tumors (91%) displayed a lobular architecture composed of solid and nested growth of epithelioid cells with plasmacytoid features in a myxoid or angiomatous stroma. Scattered cytologic atypia and rare duct differentiation were frequently noted. Three tumors with confluent cytologic atypia, infiltrative growth, and lymphovascular invasion were classified as malignant. By immunohistochemistry, the tumors were positive for S100, SOX10, keratins AE1/AE3, CK5/6 and CK7, and PLAG1. Local recurrence and bilateral pulmonary metastasis were observed in a patient presenting with a histopathologically benign-appearing tumor. Two patients with malignant tumors experienced local recurrences, and 1 developed metastasis to soft tissue, lung, and mediastinal lymph nodes. All patients are currently alive, all but 1 with no evidence of disease after a median follow-up interval of 96 months (range: 2 to 360 mo). In conclusion, acral myoepithelial neoplasms show distinctive and reproducible histopathologic and immunohistochemical features. They are best regarded as a distinctive subset of mixed tumors with features reminiscent of their salivary gland counterparts. While most tumors pursue a benign disease course, histopathologic features appear to be a poor indicator of prognosis.

Sweat Gland Tumors Arising on Acral Sites

“…Similarly, by analogy to their salivary counterpart, rearrangements of the PLAG1 gene have been identified in cutaneous mixed tumors, 33,34 as observed in our study that demonstrated TRPS1::PLAG1 fusion in 75% of the cases, with no morphologic differences in the nonrearranged case. It should be noted that although no cutaneous myoepithelial tumor lacking an epithelial component, that is, myoepithelioma, was included in our study, the recent series by Mehta et al 35 demonstrated immunohistochemical expression of PLAG in this setting, which could reflect a similar gene rearrangement.…”

EWSR1::NR4A3 gene fusion in a cutaneous atypical myoepithelial neoplasm

“…At this anatomic location, cytologic atypia is common. Although most of these tumors follow an indolent clinical course, histopathologic features have not been shown to predict clinical outcomes, with some bland tumors eventually resulting in metastatic disease 11 …”

“…10 Characterization of cutaneous acral myoepitheliomas has recently been undertaken, and these neoplasms are generally characterized by sheets of epithelioid cells with prominent telangiectasia and a myxoid stroma. 11 At this anatomic location, cytologic atypia is common.…”

“…Although most of these tumors follow an indolent clinical course, histopathologic features have not been shown to predict clinical outcomes, with some bland tumors eventually resulting in metastatic disease. 11 Because dermal tumors often extend to the soft tissue and vice versa, the classification of where these neoplasms arise is controversial. 7 Because of this overlap and scarcity of literature on myoepithelial carcinomas solely of the skin, the discussion will include those neoplasms arising in the soft tissue.…”

Cutaneous Syncytial Myoepithelioma with Positive CD34 Immunohistochemical Staining: An Unusual Tumor and a Challenging Diagnosis

“…Only one patient experienced a local recurrence 51 months after surgery, despite the initial excision being performed via a shave biopsy with a positive deep margin [ 3 ]. In contrast, some authors believe that histopathologic features appear to be a poor indicator of prognosis because some myoepitheliomas, of other variants than the syncytial one, develop metastasis, although with a benign morphological appearance [ 25 ]. In addition, there is a lack of evidence regarding the timing of follow-ups and the potential need for diagnostic investigations.…”