Teratomas, Dermoids, and Epidermoids of the Head and Neck

Abstract Introduction

Cranial Epidermoid and Dermoid Inclusion Cysts Teratomas Summary

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Introduction

Teratomas, dermoids, and epidermoids are distinct lesions that have some overlapping features. Confusion and controversy persist about the general features of their origins and about their specific features, such as the cause of the "fatty" or lipid material, that often provide a radiologic clue to diagnosis. This article illustrates the spectrum of these congenital masses of the head and neck, presents some theories about their origins and embryologic development, and attempts to clarify some common misconceptions about their pathologic and radiologic characteristics.

One misconception is that an epidermoid lesion contains tissues derived from one of the three embryonic germ layers (ectoderm), a dermoid has tissues from two germ layers (ectoderm and mesoderm), and a teratoma has tissues from all three germ layers (ectoderm, mesoderm, and entoderm). However, this delineation is not completely applicable. Epidermoids are derived from ectoderm, but they are inclusion cysts lined solely by squamous epithelium. A dermoid is also an ectodermal inclusion cyst, with all its more complex tissues derived solely from ectoderm. One of the most important points is that a teratoma is not necessarily composed of tissues derived from all three germ layers. Instead, a teratoma can be defined as a true neoplasm that contains tissues that either are foreign to the primary site of origin or are histologically diverse and represent more than one of the embryonic germ layers (1,2,3,4,5,6). The designation of teratoma can be appropriate even for a lesion with tissues derived from only a single embryonic germ layer, if the tumor shows histologically divergent differentiation. Such teratomas are found in the head and neck and can be purely ectodermal but include both cutaneous and neural tissues (neural tube, neuroglia, or brain). However, as determined by means of adequate tissue sampling and thorough microscopic evaluation, up to 90% of childhood teratomas contain tissues derived from all three embryonic germ layers (6). The Table (Table 1) lists the three embryonic germ layers and some of their derivative tissues.

In this article, epidermoid and dermoid lesions are discussed together because of their similarities and since their embryologic development is almost identical. Their origins, pathologic and histologic characteristics, clinical presentation, and radiologic appearance are described. Teratomas are discussed as a group in a similar manner, with more detail presented for tumors manifesting in various locations, including cranial, the orbit, the neck, and the tongue. Radiologic characteristics of teratomas are described in terms of a differential diagnosis for lesions occurring in these sites.

Abstract Introduction

Cranial Epidermoid and Dermoid Inclusion Cysts Teratomas Summary

Source Information References