Melanoma with Underlying Regression
Bruce R. Smoller
University of Arkansas for Medical Sciences
Little Rock, AK
56 year old man with variegated, pigmented lesion on the back.
Pathological/Microscopic Findings and any Immunohistochemical or Other Studies:
in situ melanoma with underlying fibrosis, inflammation and nests of atypical melanocytes elastic
tissues stains demonstrate pattern characteristic of regression with vertical fibers pushed down to base
of melanocytic prolfieration, but still present (unlike in a scar)
- Melanoma with regression
- Melanoma with adjacent scar formation
- Dysplastic nevus with underlying fibrosis
Melanoma with underlying regression
Historically, it has been difficult to distinguish between regression and fibrosis secondary to other
causes such as previous biopsy, rupture of nearby hair follicles or other non-specific inflammatory
processes. This distinction is not one of an entirely academic nature but may well have significant
prognostic implications. The exact significance of regression remains unknown. The literate is replete
with multivariate analyses suggesting that regression is of no significance. As many articles can be
found suggesting that regression may portend a worse prognosis, especially when extensive (extending over
more than 80% of the breadth of the lesion). Some authors argue that in melanomas with underlying
regression, it is important to measure and report the thickness of the melanoma to the base of the focus
of regression. These investigators postulate that this measurement provides an indication of the deepest
point of penetration of the primary tumor and represents the truest prognostic indicator. To date, there
has been no study suggesting that regression plays a beneficial role in the biologic behavior of this
malignancy. Based upon the uncertainty regarding the significance of regression associated with
melanoma, it is important, whenever possible, to indicate the presence of regression, especially when
extensive. It is often difficult to distinguish regression from reactive fibrosis underlying a
dysplastic nevus and from scarring secondary to other processes. During this year, Dr. Kamino and her
co-workers completed a study in which they demonstrated subtle, but reproducible changes in the
distribution of elastic tissue fibers in these three conditions. In normal skin, the papillary dermis is
characterized by delicate elastic tissue fibers that are oriented perpendicular to the surface epidermis.
The reticular dermis has much more dense and broader elastic tissue fibers oriented parallel to the
epidermis. The fibrotic dermis beneath a dysplastic nevus demonstrates a similar pattern. The nests of
melanocytes within the papillary dermis are surrounded by thin elastic tissue fibers demonstrating a
"normal" vertical orientation. Areas of regression associated with a melanoma demonstrate a similar
pattern, but displaced downward. At the base of the area of fibrosis, vertically oriented elastic tissue
fibers are present. These fibers are identical in size and shape to those in the "normal" papillary
dermis, but are displaced to the base of the area of fibrosis, or regression. The broader, denser
reticular dermal elastic tissue fibers are similarly downwardly displaced, but otherwise retain their
"normal" configuration. In contrast, the fibrosis seen in a scar is lacking in all papillary dermal-type
elastic tissue fibers and all that remain at the base of the fibrosis is the reticular dermal type fibers
oriented parallel to the skin surface.
Use of elastic tissue stains can be helpful in distinguishing between melanoma with underlying
regression, benign nevus cells trapped within a fibrotic dermis, and a scar underlying a melanoma in
situ. The changes in staining patterns are characteristic and reproducible.
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