Hidden Epidermal Cyst Formation below the Umbilical Circular Keloid

Dear Editor:

As many surgical operations have been replaced by laparoscopic surgery, the number of umbilical keloid patients is gradually increasing. Epidermal cyst, one of the common benign intradermal or subcutaneous tumors, usually results from the trauma to the pilosebaceous unit in the hair-bearing area. Several previous reports have revealed that epidermal cysts can occur adjacent to the surgical incision line¹. However, to our knowledge, a report describing an epidermal cyst below an umbilical circular keloid has not been published.

We experienced three cases of hidden epidermal cyst formation below an umbilical circular keloid. All three patients had no previous injury history from needles such as intralesional injection. In two middle-aged female with tenderness of the keloid, a ruptured epidermal cyst was identified by incisional biopsy (Fig. 1A~H). When we tried the incision, pus and keratinous materials were evacuated (Fig. 1B). Both patients were treated with empirical antibiotics and pus drainage with sterile packing dressing.

Fig. 1. (A~D) Patient 1: a 43-year-old female with a solitary, 3-cm sized, protruding, fluctuant, keloidal mass on the umbilicus area. (A)Initial visit. (B) After incisional punch biopsy and drainage. Purulent discharge with keratinous material. (C) One-week follow-up. (D) Some neutrophilic collections in dermal portion (H&E, ×200). (E~H) Patient 2: a 58-year-old female with a solitary, painful, indurated, keloidal mass with a surrounding erythematous patch on the periumbilical area. (E) Initial visit. (F) After incisional punch biopsy and drainage. (G) Two-month follow-up. (H) Inflamed and ruptured epidermal cyst formation in the keloid. Multinucleated giant cells and some macrophages (H&E ×100). (I~K) Patient 3: a 78-year-old male with recurrent tenderness and pain around an umbilical keloidal scar. (I) Initial visit. (J) Surgical incision and dissection were performed. A well-demarcated cystic mass with hair follicle invagination was observed. (K) Epidermal cyst formation in the keloid (H&E, ×100). We received the patient's consent form about publishing all photographic materials.

The other case was a 78-year-old male presenting with recurrent pain and discomfort around an umbilical keloid (Fig. 1I). An ultrasonographic examination confirmed the formation of epidermal cyst below the scar, and excision of the cyst was performed accordingly. The pathology examination revealed a well-demarcated cystic mass with hair follicle invagination (Fig. 1J, K).

Although the pathophysiology of this condition is not fully understood, several relevant factors can be inferred. First, injury is one of the risk factors for epidermal cyst formation. Any post-operative site is vulnerable to formation of epidermal cyst. Trauma may stimulate epithelial proliferation and create the cysts. Second, because the umbilicus is originally a curled structure, it is difficult to suture each layer by aligning it². As laparoscopic surgery requires multiple layers of suture, it is possible to cause more of the epidermis to be entrapped in the final wound. If epithelial elements are retained within the infolded dermoglandular structures or at any other skin closure, epithelial inclusion cyst may occur. Third, because keloid formation occurs as a result of abnormal wound healing, a history of poor healing in the umbilicus area can be considered a risk factor for both keloids and epidermal cysts.

In such a condition as described above, surgical intervention may be necessary in most patients. The area around the umbilicus is warm, humid, and difficult to keep clean; it is an environment in which cyst inflammation can easily occur. If the epidermal cyst is left untreated, secondary infections can occur, leading to abscesses, necrosis, scarring, cellulitis, or even sepsis³,⁴.

In addition to an epidermal cyst, there are many other causes of inflammation around the umbilicus. In patients with suspected inflammation, it is important to perform appropriate imaging test⁵. Also, a patient's predisposing factors (e.g., poor hygiene, diabetes mellitus, obesity, corticosteroid use, and immunosuppression) should be identified at the time of presentation⁵.

We reviewed three cases of hidden epidermal cyst formation below the umbilical circular keloid. Rapid and appropriate intervention has been delayed in numerous keloid patients. We hope that many dermatologists will review this condition after reading this report.