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Congenital Giant Keratinous Cyst Mimicking Lipoma: Case Report and Review Samrat Sabhlok, Ketki Kalele1, Asmita Phirange, Supriya Kheur1

Abstract From the Departments of Oral Epidermal cysts represent the most common cutaneous cysts. They arise following a localized and Maxillofacial Surgery, 1 inflammation of the hair follicle and occasionally after the implantation of the epithelium, Oral Pathology and Microbiology, following a trauma or surgery. Conventional epidermal cysts are about 5 cm in diameter; Dr. D.Y. Patil Dental College and Hospital, DPU, Pimpri, Pune, however, rare reports of cysts more than 5 cm are reported in the literature and are referred as Maharashtra, India “Giant epidermal cysts.” Epidermal cysts although common, can mimic other common benign lesions in the head and neck area. A thorough clinico‑pathologic investigation is needed to diagnose these cutaneous lesions as they differ in their biologic behavior, treatment, and Address for correspondence: prognosis. We report a case of a giant epidermoid cyst in the scalp area of a young female Dr. Samrat Sabhlok, patient which mimicked lipoma on clinical, as well as cyotological examination. We also Department of Oral and Maxillofacial Surgery, Dr. D.Y. Patil present a brief review of epidermal cysts, their histopathological differential diagnosis, and Dental College and Hospital, their malignant transformation. DPU, Pimpri, Pune ‑ 411 018, Maharashtra, India. Key Words: Giant epidermal cyst, histopathology, keratinous cyst, scalp E‑mail: [email protected]

What was known? Epidermal cysts are the common keratinous cysts of skin.

Introduction These epithelial, walled cysts vary from a few millimeters Epidermal cysts represent the most common cutaneous to 5 cm in diameter. These cysts are mobile unless [1] cysts. The epithelium inclusion cyst, Pilar or Trichilemmal fibrosis is present. They are most often benign and can cyst, Dermoid cyst, and Steatocystoma are the different recur after incomplete excision. In some cases, malignant types of keratinous cysts.[1] Epidermal/keratinous cysts are degeneration occurs, resulting in the direct invasion of [3] asymptomatic. In the past, these cysts were also known adjacent tissues and distant metastases. as sebaceous cysts. However, now the term “sebaceous Conventional epidermal cysts are <5 cm in diameter. cyst” has fallen into disuse.[1] One of the reasons for this Giant epidermal cysts with a diameter of 5 cm or more comes from analysis of the lipids from epidermal cysts by are rare but have been reported.[4] We report a case of a thin layer chromatography.[2] This revealed characteristic giant epidermal cyst on the posterior scalp. patterns of lipid classes which resembled much more closely to the lipid pattern of epidermis than that of the Case Report sebaceous gland. This data provides biochemical support A 23‑year‑old female patient was referred to our for the view that none of the epidermal cysts is of institution with a huge mass on the posterior scalp near [2] sebaceous origin. Current terms include epidermal cyst, the midline. The patient’s parents gave the history that keratin cyst, epithelial cyst, and an epidermoid cyst. the mass on the posterior scalp was present since birth Epidermoid cysts are dome‑shaped lesions that often which gradually increased to the present size. arise from a ruptured pilosebaceous follicle. They are The swelling was painless and was gradually enlarging. asymptomatic, slowly enlarging, firm to fluctuant lesions On examination, there was a well‑demarcated solitary that frequently appear on the trunk, neck, face, and scrotum or behind the ears. Occasionally, a dark keratin plug (a comedo) can be seen overlying the cyst cavity. This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows Access this article online others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms. Quick Response Code: For reprints contact: [email protected] Website: www.e‑ijd.org

How to cite this article: Sabhlok S, Kalele K, Phirange A, Kheur S. Congenital giant keratinous cyst mimicking lipoma: Case report and DOI: 10.4103/0019-5154.169160 review. Indian J Dermatol 2015;60:637. Received: March, 2015. Accepted: July, 2015. Sabhlok, et al.: Congenital giant keratinous cyst pear‑shaped sessile swelling in the occipital region near the midline measuring 7 cm × 6 cm in its greatest dimension [Figure 1]. On physical examination, no other swelling was noted elsewhere in the body. The skin overlying the swelling was normal in color and texture but slightly stretched. The absence of hair on the surface of the swelling was noticed. There was no local rise in temperature associated with the swelling. The swelling was nontender, soft and putty in consistency, and mobile over the underlying structures. The surface of the swelling was lobular with smooth bumps. The swelling was fluctuant, compressible, and nonpulsatile. On radiographic examination, a soft tissue shadow of the cyst was seen at the occipital region without any bony erosion.

On the basis of the clinical examination, a provisional Figure 1: Large pear‑shaped swelling on the scalp clinical diagnosis of lipoma was made. Fine‑needle aspiration cytologic (FNAC) was carried out to evaluate the nature of the contents of the cyst. Contents of the lesion were aspirated using a wide bore needle and was sent for microscopic examination. The section revealed the presence of numerous cells with empty cytoplasm and peripherally placed nucleus resembling adipocytes. Few keratin strands were also seen in the section. The FNAC diagnosis was given as lipoma. Surgical excision of the cyst was then planned under general anesthesia. The specimen was sent for histopathological examination [Figure 2]. Findings Soft tissue was received in 10% formalin. The tissue was soft, putty, and fluctuant inconsistency. On cutting the mass, muddy paste got extravasated [Figure 3], which resembled soggy keratin. The histological section revealed cyst wall and a cystic lumen with overlying epidermis [Figure 4]. The cyst wall showed signs of rupture and disintegration. The overlying cystic epithelium is disintegrated due to inflammation and was Figure 2: Lesion excised in toto not evident in the section. Keratin flecks were seen with squamoid cells [Figure 5]. Spillage of keratin in the surrounding connective tissue provoked giant cell reaction, and many cholesterol clefts are also evident throughout the section that is usually referred to as “keratin granuloma” [Figure 6]. The histopathological diagnosis of “epidermoid cyst” was given. Discussion Keratinous cysts are common lesions formed by invagination and cystic expansion of the epidermis or of the epithelium forming the hair follicle. These cysts have a tendency to rupture very easily thereby causing foreign body reaction. Ruptured epidermal Figure 3: Extravasated muddy paste on grossing Sabhlok, et al.: Congenital giant keratinous cyst cysts have been reported in 21.3% to 38.0% of of the lesion is evident only by the presence of cases, in the literature.[5] In such cases, the nature extruded keratin flakes surrounded by inflammatory cells and foreign body giant cells producing the “keratin granuloma.”[6] In the present case, there was a rupture in the cyst causing disintegration of the overlying epithelium. Thus, commenting on which type of keratinous cyst was not possible. Hence, discussion includes brief review about general aspects and the complications of the keratinous cyst. Keratinous cysts are lined by stratified epithelium, which may keratinize either with the formation of keratohyalin, forming a horny material resembling the epidermis or without the formation of keratohyalin, forming trichilemmal keratin. Thus, keratinous cysts are divided into: • Epidermoid cysts (which consist of stratified squamous epithelium containing keratohyalin granules) • Trichilemmal cysts (which lack keratohyalin granules).[7] Basic differences between epidermoid cysts and trichilemmal cysts are given in Table 1. Figure 4: Scanner view showing cyst lumen Epidermoid cysts Epidermoid cysts are common subcutaneous cysts that can occur anywhere in the body and 7% of them occur in the head and neck. It is defined as ‑ “A simple cyst lined with stratified squamous epithelium and lumen is filled with cystic fluid or keratin and no other specialized structure.”[8] Epidermoid cysts can occur at any age from birth to 72 years; they usually become apparent in patients between 15 and 35 years. Males are more commonly affected. These are usually solitary, but multiple epidermal cysts can occur and may present as small or large masses. Thereby, epidermoid cysts which are more than 5 cm in size are termed as “giant epidermoid cysts.” Giant epidermoid cysts are comparatively rare especially in the head and neck area.[5,9] The size of the cyst is of significance as giant cysts (>5 cm) have more chances of malignant Figure 5: Keratin flecks and squamoid cells transformation as compared to conventional cysts. The present case is a case of giant epidermoid/keratinous cyst. Etiopathogenesis An epidermoid cyst is formed by the proliferation of epidermal cells within a circumscribed dermal space with

Table 1: Basic differences between epidermoid cyst and pilar or trichilemmal cyst Epidermoid cyst Pilar or trichilemmal cyst Lined by cornified epithelium, Characterized by sudden has a distinct granular layer keratinization without the formation of granular cell layer Presence of lamellated keratin Keratin is not lamallated Focal calcification is infrequent Focal calcification is frequent Derives from traumatic Trichilemmal derivation Figure 6: Keratin granuloma inclusion of epidermis Sabhlok, et al.: Congenital giant keratinous cyst retention of keratinous debris and cholesterol or sebaceous Trichilemmal cyst materials. These cysts are either congenital or acquired. These cysts are also known as Pilar cysts or Wen. They Several theories of the formation of epidermoid cysts are are known to arise from the outer root sheath epithelium known. A congenital epidermal cyst may be formed by and have a distinctive pattern of keratinization called trapping of displaced embryonic epithelial rests commonly trichilemmal keratinization.[14] Trichilemmal cysts occurring in the head and neck area.[5] An acquired epidermal are common, occurring in 5–10% of the population.[15] cyst can result from occlusion of the pilosebaceous unit These cysts usually occur in areas with dense hair follicle or implantation of viable epidermal cells in the dermis or concentrations; hence, 90% of these occur on the scalp. [5] subcutis. It can be traumatic or surgical implantation of One of the typical features of this cyst is that an epithelial elements. Human papillomavirus (HPV) type 57 or overlying punctum is normally not present. Clinically, 60 infections may be additional factors in the development these cysts are indistinguishable from the epidermoid [10] of a palmoplantar epidermoid cyst. Epidermoid cysts are cysts. There are few clinical features that may favor also seen in patients with Gardner syndrome, particularly the diagnosis of a trichilemmal cyst though none of on the face and scalp.[5] They are also seen in basal cell them are absolutely characteristic. Trichilemmal cysts nevus syndrome, and pachyonychia congenital.[11] Moghimi are firmer, and they get removed more easily through et al.[12] has described a case of perforated epidermoid cyst a surgical incision as compared to epidermoid cysts. in association with Ehlers‑Danlos syndrome. Epidermoid cysts are 4–5 times more common than trichilemmal cysts. In some of these cysts (2% of Histologically, the cystic lining is comprised of stratified cases), single or multiple foci of proliferating cells give squamous epithelium resembling epidermis. Cases having rise to proliferating tumors, often called proliferating areas of pseudostratified ciliated columnar epithelium are trichilemmal cysts or tumors.[6] Proliferating trichilemmal occasionally reported. A well‑formed granular cell layer cysts grow rapidly and are known to occur de novo is present, and the lumen is filled with degenerating also.[16] They are easily enucleable with no punctum in orthokeratin as its content. Dystrophic calcification contrast to epidermal cysts. Similar to trichilemmal cyst, and reactive foreign body reaction are commonly proliferating trichilemmal tumor (PTT) has a predilection associated with the cystic capsule. This common for the scalp but elderly females are more prone.[14,15] property of the cyst to rupture and get inflamed is in part mediated by the horny material contained in the Etiopathogenesis epidermoid cysts. Extracts of this material have been Certain authors believe that the trichilemmal cyst shown to be chemotactic for polymorphonucleocytes.[11] originates from budding of the external root sheath of Jayalaxmi et al. reported an interesting case in which hair follicles as a result of genetic aberration. In this there was increased a number of melanocytes in the type of cyst, cells undergo an abrupt transition from the basal layer, large globular cells of melanocytic origin stratum spinosum to the keratinized layer skipping the [6] in the spinous layer, and hair‑germ‑like aggregates of formation of the granular layer. The lesion is autosomal [1] basaloid cells and melanocytes.[6] dominant and can run in families. Histopathology Malignant transformation The cyst contains homogeneous eosinophilic material The feature that makes this cyst of diagnostic importance which in contrast to the lamellated keratin flakes in an is the occurrence of secondary malignancies within the epidermoid cyst. Cholesterol clefts are common in the cyst. Malignancies occurring in the cyst include basal keratinous material present within the cyst content. cell carcinoma, Bowen disease, squamous cell carcinoma, 1/4th of cysts show calcification. These cysts also show and even mycosis fungoides. Rarely, Paget’s disease and a propensity to rupture with considerable foreign body Merkel cell carcinoma have also been reported. giant cell reaction and thereby evoke inflammation in Most common malignancy associated with the epidermoid surrounding tissue like the previous cyst. cyst is squamous cell carcinoma. Basal cell carcinoma is However, only a few reports in the literature have the second most common malignancy occurring from this highlighted the immunologic nature of this reaction. The cyst. Exposure of the skin to ultraviolet radiation is the pathologic processes occurring in these cysts could be most common cause for the development of squamous attributed to: cell carcinoma. HPV infection has also been stated as • Rupture of the cyst with its accompanying one of the causes. However, Anastasiosa et al. showed no inflammation; or etiological correlation between HPV and the development • Loss of equilibrium between matrix metalloproteinases of squamous carcinoma in the small numbers of cases and their inhibitors studied by them.[13] Squamous cell carcinoma is more likely • Adiponectin released by adjacent adipocytes may to develop in an injured or chronically diseased skin.[10] regulate the inflammatory responses in the area.[16] Sabhlok, et al.: Congenital giant keratinous cyst

Table 2: Histopathological differential diagnosis Dermoid cyst Hydrocystoma Vellus hair cyst Pilar tumor (proliferating trichilemmal cyst) Greatly resemble keratinous These are lined by a layer of Lined by flattened, Represents counterpart of trichilemmal cyst cyst of epidermal type sweat duct like epithelium follicular sheath epithelium Only difference being the ‑ Contains numerous vellus These predominantly have solid appearance presence of hair adnexa hairs and soft keratinous and pushing borders and other skin appendages material Can be mistaken for squamous cell carcinoma in the cystic cavity arising from sebaceous cyst

Table 3: Differences between treatment and describes the significant differences between these two [20,21] prognosis of lipoma and keratinous cyst entities. Keratious cyst Lipoma Conclusion For complicated or larger cysts, Surgical treatment of a wider excision to ensure cyst lipomas involves simple While dealing with scalp lesions, as well as other cutaneous wall removal is required and, excision lesions, of the head and neck region differential diagnosis therefore, is associated with a of keratinous cysts should be kept in mind as these cysts greater cosmetic defect carry certain complications such as cystic rupture, abscess, Epidermal inclusion cysts require Relatively simple secondary, and infections, during their treatment. These a more careful dissection to dissection is required. cysts carry relatively more recurrence rate as compared avoid an inflammatory reaction to lipoma and certain other benign lesions mimicking from spilled cyst contents these cysts. As also, these cysts require thorough In contrast to lipomas, a Less chances of recurrence histopathological examination and close follow‑up due to retained cyst wall will more The local recurrence rate of their potential for malignant transformation. often result in cyst recurrence simple lipomas involving subcutaneous tissue is Financial support and sponsorship approximately 1-2% Nil. Conflicts of interest Various histological differential diagnosis for these cysts There are no conflicts of interest. are given in Table 2. What is new? Malignant transformation A rare case report of the giant congenital epidermal cyst with a review on various In some instances, malignant transformation of PTT cysts containing keratinous material and their malignant transformation. occurs, and this malignant lesion presents some areas reminiscent of trichilemmal keratinization but shows References [14] severe atypia and invasion of the surrounding tissue. 1. Zuber TJ. Minimal excision technique for epidermoid (sebaceous) cysts. Am Fam Physician 2002;65:1409‑12, 1417‑8, Trichilemmal carcinoma is a lesion commonly presenting 1420. as a slow growing epidermal papule, indurated plaque, 2. Nicolaides N, Levan NE, Fu HC. The lipid pattern of the [16] or nodule that may ulcerate on the face or ears wen (keratinous cyst of the skin). J Invest Dermatol and in rare instances may show the carcinomatous 1968;50:189‑94. transformation.[17] 3. Mackie RM. Tumours of the skin. In: Rook A, Wilkinson DS, Ebling FJ. Textbook of Dermatology. 4th ed., Vol. 3. St. Louis: Apart from the overall malignant transformation rate, Blackwell Mosby Book Distributors; 1986. p. 2405‑6. [18] which varies from 0.033% to 9.2% in some articles, 4. Kang SG, Kim CH, Cho HK, Park MY, Lee YJ, Cho MK. Two cases to 1.5–10% in others,[19] certain other complications for of giant epidermal cyst occurring in the neck. Ann Dermatol these cysts are infection, Cock’s peculiar tumor, abscess, 2011;23 Suppl 1:S135‑8. cutaneous horn, which make this cyst an important 5. Huang CC, Ko SF, Huang HY, Ng SH, Lee TY, Lee YW, et al. diagnostic entity.[11,20] Epidermal cysts in the superficial soft tissue: Sonographic features with an emphasis on the pseudotestis pattern. Another feature to be noted in the present case was J Ultrasound Med 2011;30:11‑7. the clinical presentation of this lesion, which mimicked 6. Jayalakshmy PS, Subitha K, Priya PV, Johnson G. Pigmented lipoma in its appearance. Even, FNAC findings revealed epidermal cyst with dense collection of melanin: A rare entity – Report of a case with review of the literature. Indian features of lipoma. However, this diagnostic discrepancy Dermatol Online J 2012;3:131‑4. between clinical and histopathological features of this 7. Tsujita‑Kyutoku M, Danbara N, Yuri T, Nikaido Y, Hatano T, lesion is significant as the biological behavior, as well Tsubura A. Basal cell carcinoma arising from a keratinous cyst as the treatment of both these lesions vary. Table 3 of the skin: A case report and review of the literature. Med Sabhlok, et al.: Congenital giant keratinous cyst

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