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Year : 2022  |  Volume : 67  |  Issue : 5  |  Page : 628
Dermatoscopy of solitary keratoacanthoma

Department of Dermatology, Venereology and Leprosy, Pramukhswami Medical College, Shree Krishna Hospital, Bhaikaka University, Karamsad, Gujarat, India

Date of Web Publication29-Dec-2022

Correspondence Address:
Pragya A Nair
Department of Dermatology, Venereology and Leprosy, Pramukhswami Medical College, Shree Krishna Hospital, Bhaikaka University, Karamsad, Gujarat
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijd.ijd_391_22

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How to cite this article:
Tandel JJ, Polra RV, Pillai D, Nair PA. Dermatoscopy of solitary keratoacanthoma. Indian J Dermatol 2022;67:628

How to cite this URL:
Tandel JJ, Polra RV, Pillai D, Nair PA. Dermatoscopy of solitary keratoacanthoma. Indian J Dermatol [serial online] 2022 [cited 2023 Feb 7];67:628. Available from:


A 21-year-old female presented with a complaint of an asymptomatic, blackish, and elevated lesion over her back for 3 years. Cutaneous examination showed a single, nodule measuring approximately 2 cm in diameter with a hyperpigmented border and scaling in the center over the left lower back [Figure 1]. The dermoscopy done by dermalite DL 4 in polarized mode with 100 × magnification showed thick yellowish-white scales surrounded by white structureless zones encircled by brownish to black area. Red dots with arborizing vessels were seen in the center of the lesion [Figure 2]. An excisional biopsy was done. Histopathology showed a large, well-differentiating squamous tumor with central keratin-filled crater. The surrounding epidermis forms a lip around the invaginating crateriform tumor. The tumor is comprised of bland squamous cells with eosinophilic cytoplasm [Figure 3]a and [Figure 3]b. From the clinical appearance, dermoscopic and histopathological features diagnosis of solitary keratoacanthoma (KA) was made.
Figure 1: Single, hyperpigmented nodule with scaling measuring approximately 2 cm in diameter over the left lower back

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Figure 2: Thick yellowish-white scales (red arrow) surrounded by white structureless area (green arrow) encircled by brownish to black area (orange arrow). Red dots (white arrow) with arborizing vessels (yellow arrow) are seen in the center of the lesion

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Figure 3: (a) Large, well-differentiating squamous tumor with central keratin-filled crater 10× (H and E stain) (b) Tumor is comprised of bland squamous cells with eosinophilic cytoplasm 40× (H and E stain)

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The KA is a low grade, rapidly growing, 1–2 cm dome-shaped skin tumor with a centralized keratinous plug. It was been labeled as verrucae, vegetating sebaceous cyst, and molluscum sebaceum in past. It is further divided into different subtypes including solitary, subungual, mucosal, giant, keratoacanthoma centrifugum marginatum, generalized eruptive KA of Grzybowski, and multiple KAs Ferguson-Smith syndrome. Although recognized as benign, it shares histopathological features with squamous cell carcinoma (SCC).[1]

The peak incidence of solitary KA is between 50 and 69 years of age, with a male to female ratio of 2:1, and is common in fair skin individuals, which was in contrast to our patient.

Ultraviolet radiation, exposure to chemical carcinogens, human papillomavirus infection, immunosuppression, use of BRAF inhibitors, genetic predisposition including mutations of p53 or H-Ras, and recent trauma or surgery are different etiologies.

Most of the lesions occur on sun-exposed hair-bearing areas affecting the face, head, neck, and dorsum of extremities. Trunk involvement like in our case is uncommon. Lesions begin as a small, round pink, or skin-colored papule that undergoes rapid growth to a dome-shaped nodule with a central keratin plug giving it a crateriform appearance. It is characterized by initial rapid growth followed by a period of variable stability and spontaneous regression.

Though central keratin is more common in KA than in SCC, differentiation between the two is possible with dermoscopy and correlation with clinical and histological findings.[2]

Differential diagnosis of KA includes SCC, amelanotic melanoma, molluscum contagiosum, prurigo nodularis, metastatic lesion to the skin, Merkel cell carcinoma, nodular basal cell carcinoma, ulcerative basal cell carcinoma, nodular Kaposi sarcoma, hypertrophic lichen planus, deep fungal infection, atypical mycobacterial infection, foreign body reaction, and verruca vulgaris.

The role of dermoscopy in KA is to differentiate it from SCC and raised non-pigmented lesions [Table 1]. Dermatopathologists still debate whether KA is a highly differentiated type of SCC or a benign neoplasm that is completely different from SCC.[3]
Table 1: Differentiating features of KA, SCC, and Bowen's disease

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Dermoscopic features are common to KA and SCC like surface scales, white circles, white structureless zones, and blood spots as per described in a study by Rosendahl et al.[2] Most of which were seen in our case.

Dermatscopic histopathological correlation in KA is as follows:

  • Central yellowish-whitish scaling (keratin)—Compact orthokeratotic hyperkeratosis.
  • White circles—Acanthosis and hypergranulosis of infundibular epithelium, indicative of follicular invasion. It has the highest specificity.[4]
  • Whitish structure within the circles—Dilated follicular infundibulum with keratin plug.
  • Whitish lines and structureless areas—Keratinizing tumor cell masses.
  • Red globules within white areas—Microhemorrhage (blood spots) within the keratin.

The presence of coiled vessels is a strong clue to KA and SCC, but it is not helpful in differentiating them from actinic keratosis and Bowen's disease. The presence of central keratin was more frequent in KAs than in SCCs, thus the circle is centered around a dilated infundibulum filled with a keratin plug that is visible as a yellow or an orange clod on dermoscopy. Treatment consists of an excisional biopsy with 4 mm margins. Smaller lesions can be treated with electrodesiccation and curettage. Aggressive large tumors and perineural invasion require tissue sparing and should consider Mohs micrographic surgery. Non-surgical interventions include topical 5% imiquimod cream, topical 5% 5-fluorouracil (5-FU) cream, intralesional methotrexate, bleomycin and 5-FU, or oral isotretinoin.

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.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Zito PM, Scharf R. Keratoacanthoma. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: [Updated 2021 Nov 15].  Back to cited text no. 1
Rosendahl C, Cameron A, Argenziano G, Zalaudek I, Tschandl P, Kittler H. Dermoscopy of squamous cell carcinoma and keratoacanthoma. Arch Dermatol 2012;148:1386-92.  Back to cited text no. 2
Weedon D, Malo J, Brooks D, Williamson R. Keratoacanthoma: Is it really a variant of squamous cell carcinoma? ANZ J Surg 2010;80:129-30.  Back to cited text no. 3
Adya KA, Inamadar AC, Palit A. Dermoscopy of keratoacanthoma centrifugum marginatum. Indian Dermatol Online J 2019;10:360-2.  Back to cited text no. 4
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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]


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