Quiz 2: What is your diagnosis?

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Diagnosis: Quiz 2

Quiz 2

Answer:  Miescher's nevus

Criteria for diagnosis clinically: A tan smooth-surfaced papule on a lip is characteristic of Miescher's nevus.

Differential diagnosis clinically: There is none.

Criteria for diagnosis histopathologically: A dome-shaped papule composed of nests, cords, and strands of monomorphic melanocytes that mature with descent progressive in the dermis is a Miescher's nevus.

Differential diagnosis histopathologically: There is none.

Clinicopathologic correlation: The papule is formed of melanocytes of a nevus, and its brown hue is related to the presence of melanin in the cytoplasm of some of those melanocytes. The smooth surface cannot be explained by changes pictured in these photomicrographs because no epidermis is visualizable, it having been destroyed when the lesion was desiccated lightly prior to its being biopsied.

Options for therapy predicated on knowledge of histopathologic findings: Even though this nevus has not been removed in its entirety (melanocytes of the nevus are present at the base of the section), no further surgery is necessary because the lesion is benign.

1) Clinically and histopathologically, the melanocytic condition shown here fulfills criteria for Miescher's nevus, it being one of many different types of congenital melanocytic nevus.

2) Many a congenital nevus, including Unna's nevus, some examples of nevus spilus, and episodically a garment nevus, is not present at the moment of birth but makes its appearance weeks, months, and even years later. For purposes practical, Miescher's nevus never is present at birth. As a rule, it appears in the first few years of life and in that sense is acquired. But the findings histopathologic, in particular the extension of it routinely throughout the reticular dermis and often with signs of neural differentiation at the base of it, as is the situation here, are those of a congenital nevus. Moreover, it differs strikingly histopathologically from the common acquired melanocytic nevi, namely, those named for Clark, Spitz, and Reed.

3) Even in the absence of an epidermis, a diagnosis histopathologic of Miescher's nevus can be made without equivocation. In most instances, no nests of melanocytes are found in the epidermis of a Miescher's nevus and should they happen to be there, they usually are stationed at the dermoepidermal junction.

4) The degeneration of collagen seen as a band of homogenous amphophilic material at the surface of this lesion is a consequence of the lesion having been electrodesiccated lightly prior to its having been biopsied by saucerization technique.

5) This patient also suffers from the residual effects of acne conglobata, his face now being distorted by a rugose surface and by numerous comedones.

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