Sections of lesion on face reveals hyperkeratosis with horn and pseudo-horn cysts formation within the epidermis. Most likely diagnosis? (AIIMS Nov 2013)
a. Keratosis refers to the proliferation of keratinocytes with excess keratin production.
b. Seborrheic keratoses are very common, benign, elevated (“stuck-on”) lesions that usually occur in older individuals.
c. Histologically, these lesions reveal hyperkeratosis with horn and pseudohorn cyst formation.
d. The sudden development of large numbers of seborrheic keratoses (Leser-Trelat sign) may occur in association with malignancy.
e. This association with malignancies may also be seen with the malignant type of acanthosis nigricans, which consists of hyperpigmented areas of skin in the groin and axilla.
f. Keratoacanthomas (KAs) are rapidly growing lesions that microscopically reveal a cup-shaped lesion with a central keratin-filled crater surrounded by keratinocytes having eosinophilic (“glassy”) cytoplasm.
g. Atypia may be present, but these lesions are not considered to be malignant.
h. The histologic appearance can make differentiating keratoacanthomas from squamous cell carcinomas on a histologic basis quite difficult. The clinical history of rapid development within several weeks is very helpful in making the correct diagnosis. Most cases of KA spontaneously resolve over several months.
i. Human papillomavirus (HPV)causes several types of verrucae (warts), which are hyperkeratotic lesions and histologically reveal hyperkeratosis, papillomatosis, and koilocytosis.
j. The latter term refers to large vacuolated cells with shrunken nuclei.
k. Characteristically present are numerous enlarged keratohyalin granules. Finally, actinic (solar) keratoses, found on sun-damaged skin, microscopically show hyperkeratosis, parakeratosis, atypia of the epidermal keratinocytes, and degeneration of the elastic fibers in the dermis.
Clinically, actinic keratoses appear as irregular erythematous brown papules. When the atypia of the intraepidermal keratinocytes is extreme (full thickness), the lesion is referred to as Bowen’s disease.
These lesions are in fact carcinomas in situ since there is no invasion into the underlying dermis. If invasion were present, the lesion would be diagnostic of a squamous cell carcinoma.