Umbilical Hyperkeratotic Variant of Seborrheic Keratosis: A Diagnostic Dilemma

Seborrheic keratoses (SKs) are the most common benign epidermal tumors of the skin, usually affecting the fifth decade with equal sex predilection, although a slight female preponderance may be seen for the Dermatosis papulosa nigra variant. SKs predominantly affect the head, neck, face, and hand. We report a case of seborrheic keratosis at the umbilicus in a 66-year-old female, diagnosed based on clinical-dermoscopic-histopathological findings, due to its rarity. A 66-year-old female presented to us with an asymptomatic black-colored lesion near the umbilicus for 10 years, with a history of an increase in the size of the lesion for 1 year. She denied trauma, fever, abdominal pain, weight loss, night sweats or discharge through the umbilicus, and similar lesions in the past. Cutaneous examination revealed a brownish-black, hyperkeratotic plaque of 1.5 cm × 2 cm at the umbilicus without ulceration or serosanginous discharge [Figure 1a and b]. The alcohol swab test was negative. There was no lymphadenopathy or palpable mass in the abdomen. Rest cutaneous examination was normal. Based on history and examination findings, differential diagnoses of omphalolith, wart, SK, umbilical hernia, urachal remnants, Sister Mary Joseph’s nodule, and ectopic endometriosis were considered. Clinico-dermoscopic features of differential diagnosis of umbilical SK are reflected in Table 1.[1] Dermoscopy was performed using Dermlite DL4, Polarized mode ×10 magnification which revealed exophytic light brown and brown-black keratotic projections with fissures with scales at places [Figure 2a-c]. No comedo-like opening, milia-like cysts, vascular pattern, or blue-grey globules were observed on dermoscopy [Figure 2]. Complete excision of the lesion was performed [Figure 2d] and the sample was sent for histopathology which was suggestive of SK [Figure 3a and b]. Based on the aforementioned findings, the final diagnosis of hyperkeratotic SK at the umbilicus was reached.Figure 1: Brownish-black, hyperkeratotic plaque of size 1.5 cm × 2 cm at the umbilicus without ulceration or serosanginous discharge (a and b)Figure 2: Dermoscopy revealed exophytic light brown (yellow square) and brown-black (red circle) keratotic projections with fissures (yellow arrow) with scales (black) at places (Polarized mode ×10 magnification; [a-c]). Complete excision of lesion performed (d)Figure 3: (a and b) Lamellar hyperkeratosis, moderate papillomatosis, multiple pseudohorn cysts, moderate acanthosis comprising of basaloid and squamous cells with multiple foci of thin pigmented interlacing downward extensions of epidermis with mild perivascular lymphocytic infiltrate and moderate fibroplasia in upper dermis (H and E, a: ×10 and b: ×40)Table 1: Clinicodermoscopic features of differential diagnosis of umbilical seborrheic keratosisPostulated theories in the etiopathogenesis of SK include skin aging, ultraviolet exposure, genetics, metabolic factors, trauma, and obesity. The appearance is variable with regards to color (namely flesh-colored, brown, or black) and morphology (such as flat and macular patch-like lesions with a stuck-on appearance or raised plaque with or without scaling.[2] SK lesions are rarely more than 3 cm in diameter and occur more frequently over the face, upper trunk, and extremities particularly involving sun-exposed areas except for palms and soles. Contrary to this our case had the atypical site of involvement as umbilicus. The characteristic common dermoscopic findings for the diagnosis of SK include comedo-like openings, milia-like cysts, fissures and ridges, fingerprint-like structures, moth-eaten borders, hairpin vessels, network-like structures, and sharp demarcation.[3,4] In our case, dermoscopic findings include exophytic brown-black keratotic projections with sulci with the absence of a comedo-like opening, milia-like cysts, and vascular pattern. Complications include irritation, pain, and discomfort. Tumors may rarely arise in SKs, namely bowenoid actinic keratosis, basal cell carcinoma, Bowen’s disease, keratoacanthoma, squamous cell carcinoma, adenocarcinoma, melanoma, and eccrine porocarcinoma. The risk of recurrence arises if removal is incomplete. There is a paucity of literature on SKs over the umbilical region in the literature. In Japan, six cases of SK arising on the umbilicus have been reported. All of them were histologically of the hyperkeratotic type. In 2009, Sawada et al. described an acanthotic type of seborrheic keratosis in a 78-year-old, presenting with dark brown nodules with thick scales.[5] Recently, Mallat et al. have reported an 18-year-old male with an umbilical SK-like lesion developed after diode laser hair removal. They described no pigmented network, but a few comedo-like openings within an erythematous-light brown scaly and fissured papule, “moth-eaten” borders, and a central crust, on dermoscopy.[6] To the best of our knowledge, this is the first report of a hyperkeratotic type of SK at the umbilical region from India. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Authors’ contributions Literature search: B.B.S, S.R.T; Data acquisition: A.S.H, J.I.M; Manuscript preparation: B.B.S, S.R.T; Manuscript editing: A.S.H, J.I.M; Manuscript review: B.B.S, S.R.T. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.