What Is This Growth on the Right Chest?

A 60-year-old man presented with a large, slightly painful nodule growing on the right side of his chest in a hair bearing area. The nodule was present for many years and had grown progressively larger. At first, the nodule was asymptomatic, but had since progressed to the point of constant discomfort. On examination, the lesion was well circumscribed measuring approximately 10 × 9 cm located just medially to his right nipple (Figure). It was slightly tender, mobile on palpation, had surface telangiectasias, and pale fluctuant content.   

What's Your Diagnosis?

Answer: Giant Epidermoid Cyst

Epidermal inclusion cysts (EICs), also known as “sebaceous cysts,” are common intradermal or subcutaneous tumors that account for a significant percentage of family practice and dermatology visits. They are common among young men aged 15 to 35 years.¹ 

These cysts can be located in many tissue planes; however, they are usually adherent to the epidermis. The evolution of an EIC is slow, with most cysts growing from a few millimeters to less than 5 cm in size.^2,3 Only rarely do they grow greater than 5 cm and become a giant epidermal cyst² (Figure). Giant cysts are commonly located on the scalp, face, neck, back, and trunk, but are not limited to these areas.^3,4 

Typically, an EIC is a clinical diagnosis. It can be identified as a fluctuant mobile nodule with an area of central punctum, which drains sebaceous material.⁵ If there is any question of the etiology of these nodules, magnetic resonance imaging without contrast is the imaging modality of choice because of its ability to assess soft tissue structures. These cysts usually run an indolent course until they become either infected or too large, thus causing pain. Other than pain, the cyst can also alter a patient’s morale due to the cosmetically disfiguring effects. Symptomatic cysts can be removed by surgical excision. 

Differential Diagnosis 

The differential diagnoses of an EIC include ganglion cyst, lipoma, neurogenic tumor, myxoid tumor, nodular fasciitis, and dermatofibrosarcoma protuberans.^4,5

Associated Syndromes

In patients with multiple EICs, the physician should be keen to exclude a gastrointestinal neoplasm, due to the association with Gardner syndrome.⁴ Up to 53% of patients with Gardner syndrome have multiple EICs, in addition to intestinal polyposis, osteomas, and thyroid nodules.⁴ Other related syndromes include basal cell carcinoma nevus syndrome and pachyonychia congenital.^4,5

Histology

The epidermal cyst wall, or “sac”, contains stratified squamous epithelium.¹ The cavity is filled with laminated layers of keratinous material. If the cyst ruptures, it can resemble a foreign body inflammatory granulomatous reaction due to release of the “sac” content in the dermis. This may in turn become a keratin granuloma.⁶ 

Etiopathogenesis

Though there are no definitive explanations of how EICs form, a few theories exist. One theory suggests that EICs form as a result of migration of epidermal cells into the dermis at an unknown point in embryologic development.⁴ An alternate theory lists damage to the integumentary system as a possible mechanism.⁴ Though these theories exist, there is insufficient evidence to ascertain whether one theory is superior to the other.⁴ 

Additionally, rare cases of EICs undergoing malignant transformation exist in the literature. One study of 3300 cases of EICs by Bauer and Lewis found a 2% transformation rate of epidermal cysts into squamous cell carcinoma, with a majority of the carcinomas being well-differentiated.⁷ Some researchers suggest that the actual rate of malignant transformation may be higher, as a large number of EICs are removed in physician offices and are therefore never examined microscopically. Another study by Paliotta and colleagues revealed that the association between EIC of the breast and transformation into malignancy was approximately 12%.⁶ Malignant transformation of an EIC occurs more frequently when located on the breast in comparison to other anatomic locations. This is supported by the thought that EICs located on the breast develop from squamous metaplasia of the mammary duct epithelium.⁶ 

Once an EIC is formed, it begins to grow in size due to the accumulation of cystic fluid or epithelial and keratinous debris. Furthermore, EICs are formed 

by the inclusion of keratinizing squamous epithelium in the dermis. The end result of this combination is a lamellated keratin filled cyst.⁶ 

Management

The treatment for an EIC varies upon whether or not the lesion is symptomatic. If the lesion is less than 5 cm, asymptomatic, and not rapidly growing, the lesion may be observed.⁶ If the cyst has ruptured and become inflamed, then incision and drainage is recommended. After the inflammation has resolved, complete removal of the cyst by elliptical excision is the treatment of choice.⁵ Complete removal of the entire cyst wall is critical when performing an elliptical excision as the cyst will otherwise recur.² If removing an EIC greater than 5 cm, histopathologic examination is recommended to rule out malignancy.^2,5 

More on Our patient

On several occasions, while going through airport security, the patient stated that he was patted down and intensely searched by airport TSA agents as his cyst was detected on the body scanner. This led to suspicion that he was trying to sneak something illegally through a security checkpoint. Thus, he sought our advice for surgical removal. 

Conclusion

Most EICs are benign keratin-filled tumors of the skin. Small cysts are often asymptomatic; however, cysts greater than 5 cm are more symptomatic and have a higher association with malignancy.³ As result, all giant EICs should be excised completely through an elliptical excision and sent for histopathologic examination.²

Ms Urso is a student at University of Central Florida College of Medicine in Orlando, FL.

Mr Dino is with State University of New York Downstate, department of dermatology, in Brooklyn, NY.

Dr Khachemoune, the Section Editor of Derm DX, is with the department of dermatology at Veteran Affairs Medical Center, and the department of dermatology at the State University of New York Downstate, both in Brooklyn, NY.

Disclosure: The authors report no relevant financial relationships. 

References

1. Nishar CC, Ambulgekar VK, Gujrathi AB, Chavan PT. Unusually giant sublingual epidermoid cyst: A case report. Iran J Otorhinolaryngol. 2016;28(87):291-296.

2. Im JT, Park BY. Giant epidermal cyst on posterior scalp. Arch Plast Surg. 2013;40(3):280-282.

3. Kang SG, Kim CH, Cho HK, Park MY, Lee YJ, Cho MK. Two cases of giant epidermal cyst occurring in the neck. Ann Dermatol. 2011;23(suppl 1):S135-S138.

4. Houdek MT, Warneke JA, Pollard CM, Lindgren EA, Taljanovic MS. Giant epidermal cyst of the gluteal region. Radiol Case Rep. 2010;5(4):476.

5. Yagnik VD. Giant epidermoid cyst over the male breast. Clin Pract. 2011;1(1):e2. doi:10.4081/cp.2011.e2 

6. Paliotta A, Sapienza P, D’Ermo G, et al. Epidermal inclusion cyst of the breast: A literature review. Oncol Lett. 2016;11(1):657-660.