Median raphe cyst

Median raphe cyst is a very rare, benign congenital lesion occurring mainly on the ventral aspect of the penis, but can develop anywhere in the midline between the external urethral meatus and anus ¹. Median raphe cysts represent an embryologic fusion abnormality of the median raphe which may lead to formation of cyst(s) in the midline, and hence the name median raphe cyst. Median raphe cyst is benign but may become secondarily infected ². Median raphe cyst may slightly fluctuate in size throughout life. Lesions are flesh-to-yellow in appearance and may appear as continuous or intermittent from the urethral meatus to the anus ³. Median raphe cyst are most common near the glans penis, but may occur anywhere from the urethral meatus to the anus ⁴. Patients are asymptomatic. As the median raphe cyst is lined by a layer of epithelium, complete surgical excision is required to prevent recurrence ².

Several terms have been used in the past to describe median raphe cyst. It includes genitoperineal cyst of median raphe ⁵, mucoid cyst of penis ⁶, apocrine cystadenoma or hydrocystoma of penis ⁷ and epidermoid cysts ⁸. A cyst close to the meatus has been referred to as parameatal cyst ⁹. It’s still debatable if all these entities are actually same or different ¹⁰. One fact that unites these conditions is that they all reflect developmental defect in male genitalia during embryogenesis. Mucoid cyst may result from faulty closure of penoscrotoperineal raphe with sequestration of ectopic urethral mucosa ⁶. An apocrine cystadenoma or hydrocystoma has bluish hue on clinical examination, while pathological details would reveal focal areas of decapitation secretion in epithelial lining, along with a myoepithelial layer ⁷. An epidermoid cyst may result due abnormal closure of the median raphe during embryogenesis or rarely, following mechanical implantation in acquired cases ¹¹. A parameatal cyst may arise due to obstruction of paraurethral duct or anomalous fusion of urethra ¹².

Figure 1. Median raphe cyst

Median raphe cyst cause

The exact cause of median raphe cyst is unknown. Median raphe cyst may represent an embryological developmental abnormality of male genitalia or a defect in closure of the median raphe. The genital tubercle, two urethral folds and the scrotal swellings, give rise to male external genitalia. The scrotal swellings fuse in the midline to form the scrotum, which leaves a permanent surface marking in the form of median raphe. An incomplete closure of the genital or urethral fold gives rise to epithelial rest. The rest may develop into either a cyst or a canal, depending on the presence or absence of an opening on skin surface ¹³. A cyst can appear even after primary closure from split-off outgrowths of embryonic epithelium ¹³. A theory that also finds support is “tissue trapping,” in which epithelial rests may get buried during midline fusion and evolve into a cyst or canal ¹⁴. Autologous transplant of skin tissue specimens has shown the development of cysts at the transplant sites, lending credibility to the tissue-trapping theory ¹⁵. Shiraki ¹⁶, on the basis of a study of nine cases of parameatal cyst of glans penis, proposed the occlusion of paraurethral ducts resulting in cyst formation as an explanation. A congenital obliteration of these ducts hampered the physiological drainage and led to development of cysts ¹⁶. Infection and trauma are acquired contributory factors in the obstruction ¹⁷. Light and electron microscopic findings of Otsuka et al. support this theory ¹⁸. Cole and Helwig ⁶ proposed an alternative, stating that these cysts could be the result of sequestered ectopic periurethral glands of Littre. However, strong evidence in support of this explanation is still lacking.

Median raphe cyst symptoms

Median raphe cysts are mostly asymptomatic ³ and grow proportionately with body size ¹⁹. Median raphe cyst is most commonly noticed in the first decade of life; however, because of the condition being asymptomatic, the patient often presents during second to third decades of life ²⁰. Shao et al. ²¹ mentioned the mean age of presentation to be 26.7 years with a bimodal age distribution at approximately 1–10 years and 21–40 years. Navalón-Monllor et al. ²² found a slightly lower mean age (24.6 years) with similar bimodal age characteristics, having higher presentation during the first and third decades of life.

Though asymptomatic, median raphe cyst has the potential to cause psychological embarrassment and discomfort ²³. Parameatal cysts are more likely to give rise to symptoms of urinary obstruction ²⁴. These symptoms are limited to dysuria, urinary frequency, or deflected urinary stream ²⁵. Pain, if present, is an indication of infection ²¹. Rarely, hematuria, hematospermia ²¹ and difficulty in sexual function ²⁴ may be presenting complaints. A median raphe cyst near the anal region can be mistaken for hemorrhoids ²⁶. The most common reason for consultation is aesthetic ²². The more distal the median raphe cyst and earlier the age at presentation, the greater the chances of it being symptomatic ²¹. A case of appearance of median raphe cyst in the shaft of the penis following intense, prolonged sexual intercourse has been described ²⁷.

Median raphe cyst is generally solitary ²², sometimes double ³ and rarely presents as a chain of cystic swellings along the median raphe ²⁸. The chain of cysts gives a cordlike appearance and has been described as canaliform median raphe cysts ²⁹. Another variant is the presence of cysts within the raphe canal, which is an elongated tract along the median raphe ³⁰. Coexistence of a cystic-type lesion and canaliform variant in different regions has also been reported ²⁶. Videodermatoscopy can help confirm the presence of a true canal ³⁰. The cyst is always obvious on the surface; however, a case of median raphe cyst was reported from the United Kingdom in which median raphe cyst presented as nonvisible palpable swelling that was confirmed on ultrasound and magnetic resonance imaging (MRI) ³¹. Another variation in presentation could be the beginning of the condition with a single lesion with subsequent appearance of more cysts ³². The cyst very rarely may have central umbilication, giving rise to differential diagnosis of molluscum contagiosum ³³.

The cysts are generally translucent, and the penile shaft is the most common location. However, many authors have separately defined parameatal urethral cysts, whose numbers exceed those of cysts in any other location ³. Consideration of parameatal cyst as a separate condition or a form of median raphe cyst needs more discussion in the scientific community. The cyst may have a bluish hue ³⁴, which is more a characteristic of cystadenoma/hydrocystoma of the penis. Pigmented cysts appearing as brown-black in color due to presence of melanocytes and melanin pigment in the epithelial lining have also been reported ³⁵. Multiple areas are rarely involved. The majority of the cysts do not reach size in excess of 1 cm ²². However, Matsuyama et al. ³ reported that about 70% of the patients in their study had size less than 0.5 cm. Scrotal cysts tend to be larger than cysts elsewhere ²¹. Median raphe cysts with sizes in excess of 2 cm have also been reported ³⁶.

Median raphe cyst complications

Median raphe cyst may be secondarily infected and manifest as pain, tenderness, erythema, or pus discharge. About 16% of patients reported by Shao et al. ²¹ had infected cysts. The most common organism found is Neisseria gonorrhoeae ³⁷. Infection with Trichomonas vaginalis can also occur, but it is rare ³⁸. However, these are case reports of infection of the median raphe rather median raphe cyst. Staphylococcus aureus infecting median raphe cyst of the scrotum and penis has been noted in old case reports ³⁹. Infection of median raphe cyst has been uncommonly documented in recent decades. The culture of the cystic content can help confirm the infective organism. Infection is generally a phenomenon noticed after sexual intercourse. The cyst may also be traumatized by other means and become infected. Urinary obstruction, if due to a parameatal cyst, does not lead to urethritis. median raphe cysts never communicate with the urethra; however, recently, a case of an epidermoid variant traversing the corpus cavernosum has been reported ⁴⁰. Another case of median raphe cyst in the scrotum was found to mimic a serous tumor and was associated with cryptorchidism ⁴¹.

Median raphe cyst diagnosis

Median raphe cyst diagnosis is mostly clinical and is confirmed histologically. Ultrasound shows an isoechoic cystic lesion ²⁴. Ultrasound can help to rule out vascularity and continuity to overlying or underlying structures. However, it has a very limited role in diagnosis and is not frequently ordered. The use of MRI is also not encouraged and reveals low T2-weighted signal of a soft tissue lesion without any appreciable contrast enhancement ³¹. Like ultrasound, MRI also helps in determining the anatomical extent of the cyst ⁴². A urethrogram will not show any communication between the cyst and urethra ⁴³.

Median raphe cyst treatment

Spontaneous resolution has been reported ¹². Observation is another option when the cyst is small and the child is asymptomatic ¹⁴. Because median raphe cyst mostly remains symptom-free, some patients deny any active treatment ³⁴. If left untreated, median raphe cyst may rupture on its own and heal uneventfully ¹⁴. Aspiration of the cyst is associated with recurrence ²¹. Marsupialization or unroofing is not recommended, because it may lead to gaping sinus ¹⁶. However, marsupialization has been found to be effective in treating canals ⁴⁴. Median raphe canals have also been treated with incision followed by electrodessication ⁴⁵. Excision followed by primary closure remains the treatment of choice and provides cosmetically acceptable results. When the cyst lies in the prepuce, circumcision can also be performed ³⁶. A giant cyst hanging at the frenulum has been treated with excision and repair by frenuloplasty ¹⁷.

Excision is associated with excellent results, with no evidence of recurrence in 6 months ⁴⁶, 1 year ²⁴ and 4 years ⁴⁷ of follow-up. In a case series with six patients, Asarch et al. ⁴⁵ noted recurrence in one of the patients after 5 years, and the cyst was reexcised with no subsequent recurrence. One of the patients of Shao et al. ²¹ developed a fistula following excision. In a retrospective study spanning 14 years, Matsuyama et al. ³ did not identify a single case of recurrence following treatment.

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