A Case of Warty Dyskeratoma on an Unusual Location

Sir,

A 72-year-old female presented to our dermatology outpatient department with complaints of a single asymptomatic skin lesion over the left lower leg since 5 years. There was no history of any oozing, discharge or bleeding from the lesion. She denied any rapid or sudden increase in the size of the lesion; although she did admit to have applied home remedies like turmeric powder to treat the lesion. Cutaneous examination revealed a solitary, firm, skin colored to yellowish nodule with central crusting over the extensor aspect of the left lower extremity [Figure 1]. The nodule was non-tender and did not bleed on touching. Clinical differential diagnosis of keratoacanthoma (KA) and appendiceal appendageal neoplasm were considered. Histopathology of the excised nodule revealed a large cup-shaped invagination which was connected to the surface by a channel filled with keratinous material. There were several acantholytic and dyskeratotic cells in the upper epidermis. At the base of the lesion, basal cell hyperplasia, villi formation, papillomatosis, lacunae filled with acantholytic and dyskeratotic cells (corps ronds and grains) were seen [Figure 2]. The histological pattern of acantholytic dyskeratosis was seen in all the adjoining hair follicles [Figures 3 and 4]. Thus, the case was diagnosed as warty dyskeratoma. Since complete surgical excision of the nodule was performed, no further treatment was advised to the patient.

Figure 1.

Skin colored to yellowish nodule with central crusting over left lower extremity

Figure 2.

Cup-shaped invagination with villi formation, papillomatosis and foci of acantholytic dyskeratosis [Hematoxylin and Eosin ×4]

Figure 3.

Another focus depicting acantholysis dyskeratosis at base of the invagination [Hematoxylin and Eosin ×4]

Figure 4.

Suprabasal lacuna with corps ronds and grains [Hematoxylin and Eosin ×10]

Warty dyskeratoma (WD) is regarded as a benign follicular adnexal neoplasm.[1] It is characterized by solitary papule or nodule arising from the scalp, face or neck in middle-aged persons or elderly. Szymanski was the first to describe a rare tumour presenting as a solitary papule or nodule most commonly affecting the scalp, face and neck and called it a ‘warty dyskeratoma’[2] However, rare cases of multiple lesions[3] and involvement oral mucosa[4] and vulva[5] have been described.

Histologically, these lesions are characterized by 3 architectural patterns including cup-shaped, cystic and nodular variants. Sometimes combination of any of these two patterns may be seen.[1]

The striking histological features of Warty dyskeratoma (WD) are a cup-shaped epidermal invagination filled with keratotic debris, grains, corps ronds and villi formation with supra basal acantholytic cells. The differential diagnosis of acantholytic dyskeratosis similar to that seen in warty dyskeratoma are Darier's disease, acantholytic dyskeratotic acanthoma, acantholytic dyskeratotic epidermal nevus, focal acantholytic dyskeratosis and squamous cell carcinoma of acantholytic type, relapsing linear acanhtolytic dermatosis and acantholytic dermatosis of genitocrural area[6] [Table 1].

Table 1.

Clinicopathological correlation in conditions characterized by acantholytic dyskeratosis

Diagnosis	Warty dyskeratoma	Darier disease	Acantholytic dyskeratotic acanthoma	Acantholytic dyskeratotic epidermal nevus	Focal acantholytic dyskeratosis	Squamous cell carcinoma acantholytic type
Clinical features	Solitary papule or nodule	Multiple warty papules over serborrheic areas, cobblestonning of the palate, v shaped nicking of the nails, longitudinal erythronychia	Solitary papules on the trunk	Linear verrucous papules and plaques (linear verrucous epidermal nevus)	Incidental acantholytic dyskeratosis seen in specimens of benign and malignant neoplasms including Basal cell carcinoma, dermatofibroma, keratoacanthoma and psoriasis	Verrucous, hyperkeratotic papule, plaque or nodule.
Histopathological findings	Cup shaped invagination, acantholytic dyskeratotic cells in follicular infundibular epithelium	Acantholytic dyskeratosis, corps ronds, grains in a case classical clinical presentation	Acantholytic dyskeratosis, hyperkeratosis, lack of cup shaped invagination	Acantholytic dyskeratosis within epidermal nevi	Incidental finding noted only in focal areas of benign and malignant neoplasms	Acantholytic cells, dyskeratosis, atypia, mitotic figures, absence of cyst-like configuration as seen in warty dyskeratoma

This case is described for the rarity of warty dyskeratoma occurring on the lower extremity. In this case, histopathology proved to be valuable in confirming the diagnosis.

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