Yonago Acta medica 2014;57:59–60

Patient Report

Epidermal Cyst with Ossification: A Patient Report
Hiroyuki Goto, Koji Adachi, Yuichi Yoshida and Osamu Yamamoto
Division of Dermatology, Department of Medicine of Sensory and Motor Organs, School of Medicine, Tottori University Faculty ofMedicine, Yonago 683-8504, JapanABSTRACT
Epidermal cysts are common skin tumors that are composed of a cyst wall of epidermal cells and central keratinmaterial. They rarely show ossification. A 68-year-oldman was referred to our clinic for evaluation of multiple
cysts on his left forehead, left cheek and right shoulder.
Histopathological examination revealed that all of thecysts were epidermal cysts, and focal ossification wasobserved outside the cyst on the forehead. We speculated
that chronic inflammation caused ossification around thecyst. Therefore, epidermal cyst should be included in the
differential diagnosis of cysts with ossification.

Fig. 1. Clinical feature: the tumor on the forehead.

epidermal cyst; ossification; trichilemmal

the forehead showed focal ossification outside the cyst
(Fig. 2).

Epidermal cysts are common skin tumors that are composed of a keratinocytic cyst wall and central keratinmaterial.1 They usually occur in an area with abundantpilosebaceous follicles. Epidermal cysts rarely show ossification unlike other cysts such as trichilemmal cysts.
Here we present an unusual case of an epidermal cyst
with ossification.

DISCUSSION
Epidermal cysts are common tumors that are composedof a cyst wall and keratin material. It is sometimes difficult to distinguish epidermal cysts from trichilemmal
cysts only from clinical features. An epidermal cyst has
keratohyaline granules in the cyst wall, but a trichilemmal cyst does not have such granules. In our case, keratohyaline granules were seen in the cyst wall.

Key words

cyst

PATIENT REPORT
A 68-year-old man was referred to ourclinic for evaluation of multiple cysts
on his left forehead, right shoulder andright back. He had a more than 10year history of the lesions. The sizesof the tumors were 15 mm on the forehead (Fig. 1), 20 mm on the cheek and
77 mm on the shoulder. He had a pasthistory of inflammation around thetumors. The cysts were excised undergeneral anesthesia. Each of the cysts
was composed of a mass of epithelial
cells containing keratinous material.
Based on results of histopathologicalexamination, a diagnosis of epidermal cysts was made. The tumor on
Corresponding author: Hiroyuki Goto, MD
h.gotou.19850820@gmail.com
Received 2013 December 24
Accepted 2014 January 8Fig. 2. Histopathological examination: the arrow shows the area of ossification area
outside the cyst (hematoxylin and eosin). Bar = 500 μm.

59H. Goto et al.

About one quarter of trichilemmal cysts show focal
calcification.1 It has been reported that idiopathic calcinosis of the scrotum is associated with epidermal cyst.2However, it is rare for epidermal cysts to be accompanied by ossification. There is only one such case reportin the published literature.3 That case was in the testis
with ossification inside the cyst. On the other hand, ourpatient showed ossification outside the cyst.
Satoh et al. reported that ossification might becaused by degeneration of keratin material.3 We speculate that chronic inflammation caused by repeated rupture of the cyst resulted in the ossification. When weexcised the cyst, we found that it had strongly adhered tosurrounding tissue, suggesting the presence of chronic
inflammation. In our case, when the cyst ruptured, kera-tin material would have been scattered outside the cyst,
leading to ossification around the cyst wall.
It is very rare for an epidermal cyst to show ossification, but epidermal cysts should be included in differential diagnosis of cysts with ossification.
The authors declare no conflict of interest.
References
1 Weedon D. Weedon’s skin pathology. 3rd edition. London:
Churchill Livingstone; 2010. p. 442-3.
2 Saad AG, Zaatari GS. Scrotal calcinosis: is it idiopathic? Urology. 2001;57:365. PMID: 11182365.
3 Satoh S, Yamamoto T, Aoki H, Fuzizuka I, Kubo T, OhhoriT, et al. [Epidermoid cyst of the testis: a report of 2 cases.]
Hinyokika Kiyo. 1988;34:1265-8. Japanese. PMID: 3051954.

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