Kaori Koga1, Yuichi Yoshida2, Monji Koga1, Morishige Takeshita3 and Juichiro Nakayama1
Departments of 1Dermatology and 3Pathology, Fukuoka University School of Medicine, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, and 2Department of Dermatology, Faculty of Medicine, Tottori University, Yonago, Japan. E-mail: email@example.com
Accepted February 5, 2007.
Median raphe cysts of the penis are uncommon benign lesions that affect young men. The cysts are lined with pseudostratified columnar or stratified squamous cell epithelium, mimicking the epithelial lining of the male urethra. Immunohistochemical study also indicates a histogenetic relationship with the urothelium. To our knowledge, there have been only 2 reports of ciliated epithelium in this kind of cyst published previously (1, 2). We describe here a rare case of median raphe cyst of the penis with ciliated cells, and discuss the histopathological and immunohistochemical features.
A 27-year-old man was referred to our hospital for evaluation of an asymptomatic nodular lesion on the glans penis. He had been aware of a slow-growing lesion at puberty. There was no antecedent history of trauma or infection. Physical examination revealed a smooth, soft, painless cystic nodule, 3.0 cm in diameter on the ventral surface of the penis (Fig. 1). The lesion was excised surgically under local anaesthesia.
Fig. 1. A soft cystic nodule on the ventral aspect of the penis. The glans is seen to the left side and the rest of the penis is down to the right side. The nodule is cross at the frenulum.
Histopathological examination showed an irregularly shaped empty cystic space in the dermis (Fig. 2a). No connection with the epidermis was evident. The cyst wall was lined with pseudostratified ciliated columnar epithelium (Fig. 2b). An immunohistochemical study was performed using a standard avidin-biotin peroxidase method. The luminal cells at the apical border were positive for CK7 (Fig. 3a), carcinoembryonic antigen (CEA) (Fig. 3b) and epithelial membrane antigen (EMA). No positive staining was obtained in the epithelium by CK20, α-smooth muscle actin (α-SMA), anti-S100 protein and GCDFP-15 (not shown). A diagnosis of median raphe cyst with ciliated cells was made on the basis of these findings.
Fig. 2. (a) An irregularly shaped cystic space in the middle dermis (haematoxylin and eosin (H&E) ×20). (b) Ciliated columnar cells in the inner lining of the cyst wall (H&E ×100).
Median raphe cysts are relatively rare midline cysts of the male genitalia found at any point from the external urethral meatus to the anus and considered to be an embryological developmental abnormality (3). They develop mainly on the ventral aspect of the penis in young men (4). Histological study usually reveals the presence of irregular cystic cavity. Their epithelial lining cells consist of columnar stratified, pseudostratified or squamous cells, according to the urethral segment origin of the lesion (3). In the present case, we found CK7+, CEA+, and EMA+ ciliated columnar cells in the lining of the cyst wall.
Fig. 3. Apical epithelial cells were diffusely stained by (a) CK7 and (b) carcinoembryonic antigen (×100).
Ciliated epithelial cells are present in the respiratory tract, middle ear, uterus and oviducts, ependymal epithelium of the central nervous system and ductulus efferens of the testis in human adults (5). Several developmental cutaneous cystic lesions in the skin, which have a ciliated columnar epithelium, have been reported (6–8). They have been given various names, such as bronchogenic cysts, vulvar cysts and cutaneous ciliated cysts according to their topographical location. Differential diagnosis of our case includes cutaneous ciliated cysts. However, cutaneous ciliated cysts typically affect the lower extremities or buttocks of women and have been regarded as Mullerian remnants (7). In men, the origin is thought to be ciliated metaplasia of the eccrine sweat glands. In our case, immunostaining for CK7 confirmed a urothelial interpretation and immunostaining for CEA is probably related to the dysembryogenic cloacal nature, suggesting a median raphe cyst as well as the results found in other studies (9, 10). Ciliated cells of a median raphe cyst are considered to be derived from metaplastic changes in the urothelium, secondary to irritation or local stimulation (2, 5).
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