Dermoid and epidermoid tumors

Robert Grant MD (Dr. Grant of the Edinburgh Centre for Neuro-Oncology has no relevant financial relationships to disclose.)
Edward J Dropcho MD, editor. (Dr. Dropcho of Indiana University Medical Center has no relevant financial relationships to disclose.)
Originally released March 14, 1995; last updated May 18, 2015; expires May 18, 2018

This article includes discussion of dermoid and epidermoid tumors, cholesteatoma, dermoid cyst, epidermoid cyst, pearly tumor, dermoid tumors, and epidermoid tumors. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

The author reviews dermoid and epidermoid tumors in the brain and spine. Tumor cysts arise from ectopic ectodermal cells that are retained within the neural groove during early gestation. These tumors often present with isolated cranial neuropathy in adulthood. CT and MRI may have characteristics similar to arachnoid cysts, but MRI usually shows restricted diffusion. Over 5% have atypical MR appearance and almost 60% of these are misdiagnosed. Complete removal at first operation is desirable for long-term cure, but the cyst wall often adheres to surrounding structures, including nerves and blood vessels, and extensive resections are associated with high rates of early or delayed postoperative deficits or hemorrhage. Total resection is possible only in 50% to 70% of cases. Malignant transformation to squamous cell carcinoma occurs rarely.

Key points

 

• Most epidermoids and dermoids are developmental in origin.

 

• The MRI appearances of epidermoids and dermoids are usually characteristic, but 5% have atypical appearance.

 

• Epidermoids and dermoids are potentially curable.

 

• During surgery it is important to minimize the spread of the cholesterol crystals to prevent aseptic meningitis or ventriculitis and avoid tissue adherent to vessels to prevent delayed ischemia or hemorrhage.

 

• Perioperative morbidity (20%) and mortality (7%) remains high, particularly if total resection is attempted.

 

• Late recurrence is common with incompletely resected tumors.

Historical note and terminology

The first description of an epidermoid has been attributed to Pinson, an artist in the School of Medicine in Paris, who made a wax model of a smooth cyst at the cerebellopontine angle in 1807 (Mahoney 1936). It was not until 1829 that Cruveilheir, a French pathologist, first recognized epidermoids as a specific entity and called them "cholesteatomas" (Cruveilheir 1829). Epidermoid and dermoid tumors are classified by the World Health Organization under the heading of Other CNS Neoplasms: Cyst and Tumor-like Lesions (Kleihues et al 1994). Medical literature uses the terms "cysts" or "tumors" interchangeably to describe "epidermoids" and "dermoids." Along with craniopharyngiomas, Rathke cleft cysts, germinomas, and nongerminomatous germ cell tumors they are referred to as "dysontogenetic" (Niikawa et al 1992). Malignant transformation does occur and can be classified using Hamlat's criteria as (1) initial malignant transformation of epidermoid cyst, (2) malignant transformation from remnant epidermoid cyst, (3) malignant transformation from dermoid or epidermoid cyst, (4) malignant transformation with leptomeningeal carcinomatosis, (5) other malignancies arising from benign cysts (Hamlat et al 2005).

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