Answer: Solar lentigo
Criteria for diagnosis
histopathologically: Orthokeratosis, nubbins of
pigmented epidermal keratocytes, and a slightly increased number of
melanocytes at the dermoepidermal junction are features of a solar
Differential diagnosis histopathologically:
There is none.
Criteria for diagnosis clinically: A tan,
sharply circumscribed macule on sun-damaged skin is characteristic
of a solar lentigo or flat seborrheic keratosis.
clinically: Clinically this lesion could be a basal
cell carcinoma, Bowen`s disease or, given the close proximity of a
scar, even a melanoma. Biopsy is necessary to come to the correct
Clinicopathologic correlation: The
central, irregularly pigmented papule is mirrored by a thickened
epidermis with basal melanin hyperpigmentation.
Options for therapy predicated on knowledge of
histopathologic findings: The lesion is benign and
therefore no therapy is needed.
1) Solar lentigo and reticulate seborrheic keratosis are
different names for the same pathologic process at different stages
of its development.
2) They usually develop on sun-damaged skin and therefore the
presence of solar elastosis in the upper part of the dermis is
typically seen by light microscopy.
3) Horn pseudocysts are tunnels of infundibular epidermis that
contain corneocytes arranged in either basket-woven or laminate
fashion, or both. They are characteristic of seborrheic keratosis
but have not formed yet in solar lentigo, in which orthokeratosis
with corneocytes arranged in laminated fashion is usually