What Is This Pink Nodule on the Gluteal Cleft?

A 45-year-old man presented with a pink nodule on the superior left buttock, approximately 1 cm lateral of the gluteal cleft  (Figure). The patient reports that the area gets inflamed and tender to the touch, preventing him from comfortably sitting. He also reports occasional serosanguinous drainage. The patient denies associated fever, weight loss, or night sweats. On physical examination, there was an approximately 2-cm x 2-cm well-circumscribed, pink nodule with surface ulceration and surrounding erythema. The lesion was not biopsied.

What Is The Diagnosis?

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Pilonidal Sinus

First described by O.H. Mayo in 1833 and again in 1847 by A.W. Anderson, pilonidal disease is a chronic, suppurative condition of the sacrococcygeal region.¹ The nomenclature arises from the Latin term for hair, pilus, and nest, nidus, translating to a nest of hairs.² Although previously thought to be a congenital malformation, pilonidal disease is now more widely considered an acquired entity.¹ The pathophysiology involves a sinus tract growing under the skin or from the hair follicle. It is believed that hair becomes trapped in the intergluteal sulcus and penetrates down into the subcutaneous tissue. There, anaerobic microorganisms cause inflammation and possible infection and/or abscess formation.³

Pilonidal sinus is estimated to affect 26 per 100,000 people, with 70,000 Americans affected annually.⁴ Men are affected twice as commonly as women, and the average age of presentation is between 15 and 30 years.⁵ Women may present sooner due to the earlier onset of puberty. Risk factors include hair in the gluteal crease, obesity, sedentary lifestyle, and local trauma.⁶

Pilonidal sinus, also known as pilonidal cyst, arises in the hair follicles as an abscess or a sinus tract with intermittent discharge. Acutely, a pilonidal cyst presents with tenderness, pain, and erythema at the top of the gluteal cleft.⁵ Infrequently a patient can be asymptomatic with the lesion discovered on routine examination. The cyst can become chronic, in which the cavity drains serous or purulent discharge through a sinus, with or without added pressure.⁷ The chronic form can vary in presentation and may be complicated by recurrent infection, abscess, and/or cellulitis.⁸ The presence of one or several pits connecting to an epithelialized tract aids in the diagnosis of an infected pilonidal sinus(es).⁵ Most often a pilonidal sinus occurs in the sacrococcygeal region, but it can present anywhere in the body, including the axilla, umbilicus, genital region, and between the fingers.

Microscopically, the tracks of a pilonidal sinus are composed of vascular pyogenic granulation tissue with loose, free hairs within the sinus.¹ Various cells including lymphocytes, neutrophils, and macrophages can be seen infiltrating the cyst. Keratin plugs and debris can be viewed lying within isolated midline pits or pits connecting with the primary sinus.⁹

The potential differential diagnoses for pilonidal sinus include perianal abscess, hidradenitis suppurativa (HS), anal fistula, perianal tuberculosis (TB), and squamous cell carcinoma (SCC) (eTable). Diagnosis is decided with a thorough history and physical and clinical judgement.

Diagnosis is clinical and does not require further imaging, laboratory testing, or biopsy. Ultrasound can be useful in evaluation prior to excision of pilonidal disease, as it can detect the full extent of sinus tracts prior to excision compared with palpation alone.¹

Treatment can be divided into  operative or nonoperative approaches or a combination of both. Patient presentation and clinical judgement should guide treatment choices. Conservative management consists of epilation and hair removal, phenol injections, incision and drainage (I&D), platelet-rich plasma (PRP), laser therapy, and fibrin and thrombin products. If infection and abscess are not present, epilation via waxing, shaving, or laser for hair removal can be beneficial. A pilot nonrandomized cohort study at an Army community hospital demonstrated that nonexcisional therapy with an emphasis on hair control led to decreased operations and near-normal return to work.¹³

Phenol injections have proven efficacious in conjunction with debridement. Phenol works by denaturing proteins and is thus effective in denaturing the keratin in hair follicles.³ An added benefit is the anesthetic properties of phenol allowing for minimal pain during the procedure. Curettage is performed first to remove debris and granulation tissue. After protecting the skin, phenol solution is injected, allowed to sit for 1 to 3 minutes, and then aspirated.⁵ Patients often require multiple treatments. I&D has commonly been employed as a treatment method, allowing for quick and effective pain resolution. A study using a military patient cohort found that I&D prior to definite surgery yielded a lower recurrence rate in patients treated with surgery alone (16% vs 34%, respectively).¹⁴ Patients presenting with abscess or infection will require I&D. PRP and laser therapy have been emerging as new players in the conservative management of pilonidal disease. Both require multiple treatments and increased evidence is required to prove efficacy.

Although many surgical approaches have been defined, none are considered the standard for treatment. These include curettage, surgical excision, unroofing, advancement flaps, cleft lift closure, and negative pressure wound therapy. Fibrin glue in conjunction with surgical excision yielded a decreased length of hospital stay, decreased volume of drainage, and higher patient satisfaction.¹

Secondary infection and abscess can further complicate a pilonidal sinus; however, recurrence is the major consequence associated with pilonidal disease.¹ Risk of recurrence is dependent on number of sinus tracts, shape, diameter of the sinus, and the duration of follow up.¹⁵ Inadequate excision has also been shown to lead to recurrence. Postoperative complications include delayed wound healing, wound breakdown, and pain at the surgical site. Obesity and smoking are both cited as risk factors for postoperative complications.¹⁵

Due to the size and open nature of this lesion, our patient was referred to a plastic surgeon for surgical management. He was lost to follow-up.

The pathophysiology of pilonidal disease involves a sinus tract growing under the skin or from the hair follicle. The potential differential diagnoses for pilonidal sinus include abscess, HS, anal fistula, and SCC. Diagnosis is clinical and does not require further imaging, although ultrasound can be used to detect the full extent of sinus tracts prior to excision. Conservative management for pilonidal sinus includes epilation and hair removal, phenol injections, I&D, and fibrin products. PRP and laser therapy are emerging as new treatments, but efficacy has not been proven. Surgical options include curettage, surgical excision, unroofing, advancement flaps, cleft lift closure, and negative pressure wound therapy. 

Ms Shamloul is a medical student at Philadelphia College of Osteopathic Medicine in Philadelphia, PA. Dr Khachemoune is on faculty at the Veterans Affairs Hospital and SUNY Downstate Dermatology Service in Brooklyn, NY.

Disclosure: The authors report no relevant financial relationships.