An unusual nodular growth on a long-standing facial plaque

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Nevus sebaceous is associated with an increased risk of developing various secondary tumors. The most frequently observed adnexal tumors arising from nevus sebaceus include syringocystadenoma papilliferum, trichilemmoma, trichoblastoma, and various sebaceous neoplasms.^[1] We report a case of a female in her sixties who presented with a 6-month duration of protuberant growth over an asymptomatic plaque on her left cheek that has been present since birth. There was no history of oozing or bleeding from the lesion. There were no other systemic symptoms. She also had photoallergic contact dermatitis involving her face and neck for 2 months, managed with topical steroids and sunscreen. She was on regular medication for her diabetes mellitus, systemic hypertension, and asthma.

Cutaneous examination revealed a single well-defined skin-colored to hyperpigmented mammilated exophytic nodule of size 4 × 2 cm with the surface showing nodularity and verrucous changes over her left cheek [Figure 1]. A few areas appear with a yellowish tint secondary to turmeric application as per the patient’s history. Systemic examination was unremarkable. Clinical differentials of nevus sebaceous for the lesion since birth, with trichoblastoma and syringocystadenoma papilliferum as secondary changes, were considered. Histological examination revealed hyperkeratosis, papillomatosis of the epidermis with sebaceous hyperplasia having more lobules in the dermis and at places communicating with the epidermis directly, suggestive of nevus sebaceous [Figure 2]. In addition, there were varied-sized lobules in the dermis composed of abundant basaloid cells with fewer mature sebocytes interspersed, suggestive of sebaceoma [Figure 3]. The patient was surgically treated with Z-plasty. On further follow-up, the patient did not report recurrence of lesions.

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Figure 1: A single well-defined skin-colored to hyperpigmented mammilated exophytic nodule of size 4 × 2 cm with the surface showing nodularity and verrucous changes over her left cheek. A few areas appear with a yellowish tint secondary to turmeric application.

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Figure 2: Histopathological image shows hyperkeratosis and papillomatosis (yellow arrow) of overlying epidermis. There is sebaceous hyperplasia with more lobules seen in the dermis (red arrow). Along with varied sized lobules in dermis composed of abundant basaloid cells. (Hematoxylin & eosin x100).

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Figure 3: Histopathological images show lobules in dermis composed of abundant basaloid cells (white circle) and less of mature sebocytes (red circle) (Hematoxylin & eosin x200).

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Nevus sebaceous, also referred to as Jadassohn’s nevus or organoid nevus, is a rare, congenital, benign cutaneous hamartoma commonly involving the head-and-neck region. These nevi typically appear at birth and enlarge in size with secondary changes noted over puberty. It affects approximately 0.3% of newborns, with no sex predilection.^[2] In adulthood, they can subsequently give rise to secondary neoplasms in around 20% of cases, usually seen after the age of 40 years. The hamartomatous involvement of both the epidermis and dermis in the nevus sebaceous creates an environment conducive to the development of various secondary neoplasms. Studies have identified over 40 different types of secondary neoplasms associated with nevus sebaceous. In a study by Idriss et al., secondary neoplasms were found in 21.4%; out of that, 18.9% were benign, and 2.5% were malignant neoplasms.^[3] Trichoblastoma was the most common tumor, followed by syringocystadenoma papilliferum in that study.^[3]

Sebaceous neoplasms can rarely develop in the background of nevus sebaceous. Secondary sebaceous neoplasms are observed in 3.3% of cases, with sebaceoma accounting for 1.3–2.2%.^[1,3] Clinically, the tumor is typically located in the head-and-neck area. These tumors are more frequent in females, with a higher incidence in the elderly population. Histologically, sebaceoma is characterized by the predominance of immature, monomorphic sebocytes, with >50% of tumor cells being basaloid cells. The basaloid cells exhibit distinct growth patterns, including rippled, labyrinthine/sinusoidal, verruca/seborrheic keratosis-like, carcinoid-like, and rarely desmoplastic type, along with infundibulocystic structures, and squamous metaplasia favoring sebaceous differentiation. Mitoses are seen strikingly in some tumor lobules; however, cytologic atypia is mild, and necrosis is typically absent.^[4,5] Although immunohistochemistry can aid in challenging cases, it was not performed in the present case, as the diagnosis of sebaceoma was confidently established based on classical histomorphological features, in the absence of significant cytologic atypia or infiltrative growth.

Our patient presents with a nevus sebaceous complicated by secondary sebaceoma, a rare occurrence. This highlights the importance of clinicopathological confirmation and confirmation of secondary neoplasms/changes noticed over the nevus sebaceous. Moreover, it is imperative to consider these rare neoplasms as part of the differential diagnosis in such cases, enabling early diagnosis and prompt surgical intervention.