In 1927 Bloch1 described benign non-nevoid melanoepithelioma of the skin and subdivided it into two types. Type I consists of a mixture of basal cells, prickle cells, and highly dendritic melanocytes. Type II is composed mainly of deeply pigmented small cells of basal type.
Review of Literature
Since Bloch's time many authors have referred to these tumors under a bewildering variety of names and offered contradictory interpretations of their nature and classification (Table 1). This confusion can be traced to several factors in Bloch's original publication. Bloch was one of the exponents of the thesis that nevus cells are modified melanocytes, and that epidermal melanocytes are modified basal cells. Therefore, when he found pigmented epidermal tumors without the formation of nevus cells, he called them "non-nevoid" in distinction from pigmented nevus cell tumors. He made no distinction between lesions consisting of pigmented Malpighian cells without dendritic melanocytes (Type II)
MISHIMA Y, PINKUS H. Benign Mixed Tumor of Melanocytes and Malpighian Cells: Melanoacanthoma: Its Relationship to Bloch's Benign Non-Nevoid Melanoepithelioma. AMA Arch Derm. 1960;81(4):539–550. doi:10.1001/archderm.1960.03730040043009
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