Quiz 14: What is your diagnosis?

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Diagnosis: Quiz 14

Quiz 14

Answer: Acanthosis nigricans

Criteria for diagnosis histopathologically: Laminate and basket-woven orthokeratosis and papillomatosis of the epidermis that has a normal granular zone and that is slightly hyperpigmented in combination with an increased number of fibrocytes in a broadened papillary dermis are findings of acanthosis nigricans.

Differential diagnosis histopathologically: Confluent and reticulated papillomatosis of Gougerot and Carteaud, reticulate seborrheic keratosis, and verrucous epidermal nevus closely resemble acanthosis nigricans histopathologically.

Criteria for diagnosis clinicall: Smooth, brown to skin-colored papillated plaques that are typically located in the axillae and inguinal folds in a fashion symmetrical.

Differential diagnosis clinically: There is none.

Clinicopathologic correlatio: The smooth papillated plaques are reflected histopathologically by orthokeratosis and papillomatosis of the epidermis and by a broadened papillary dermis. 

Options for therapy predicated on knowledge of histopathologic findings: Successful treatment of the underlying pathologic process (e.g., endocrine disease, obesity, or internal malignancies) usually leads to complete resolution of the lesions. 

1) Histopathologically, acanthosis nigricans affects both the papillary dermis and the epidermis and is characterized by epidermal hyperpigmentation, papillomatosis, melanophages, and thickening of the papillary dermis with an increased number of fibrocytes.

2) Clinically, the smooth, papillated tan-to-brown plaques of acanthosis nigricans develop in intertriginous regions. Additionally the neck, umbilicus, and mamillae can be affected.

3) Acanthosis nigricans may be congenital or acquired and has been classified into three types: "benign&" acanthosis nigricans, an autosomal dominant disorder that appears in childhood; "pseudo"-acanthosis nigricans as a result of an underlying endocrinologic abnormality, obesity or medications, such as corticosteroids and nicotinic acid; and "malignant" acanthosis nigricans, a paraneoplasia usually in connection with an adenocarcinoma of the gastrointestinal or genital tract, breast, or lung.

4) Confluent and reticulated papillomatosis, which was originally described by Gougerot and Carteaud in 1927, is a rare skin condition that has many features in common with acanthosis nigricans clinically and histopathologically. Some authors regard them as one pathologic process with the first being a variant of the second.

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