lichen sclerosus et atrophicus
Monday 13 June 2011
lichen sclerosis et atrophicus
UI:881 - Lichen sclerosis et atrophicus
Established lesions show hyperkeratosis, follicular plugging, thinning of the epidermis, and vacuolar alteration of the basal layer.
There is a broad zone of subepidermal edema with homogenization of collagen and poor staining in hematoxylin and eosin preparations.
In later lesions, this zone becomes more sclerotic in appearance and shows more eosinophilia. Basement membrane thickening also occurs.
Expression of collagen IV and VII is increased.
There is dilatation of thin-walled vessels in the zone and sometimes hemorrhage.
Beneath the edema there is a diffuse, perivascular infiltrate of lymphocytes, predominantly of T-cell type in the mid dermis.
Mast cells and liberated mast cell granules are also present.
It resembles lichen simplex chronicus.
LSA adjacent to carcinoma tends to show exaggerated epidermal thickening, basal atypia, and loss of the edematous-hyaline layer.
The appendages are usually preserved.
- In vulval lesions there is also more diversity of epidermal changes, with hyperplastic areas in mixed dystrophies.
- Vulvar LSA without associated carcinoma has a mean epidermal thickness more than three times that of extragenital LSA.
A spectrum of vascular changes occurs in LSA ranging from a rare leukocytoclastic vasculitis, to a not uncommon lymphocytic vasculitis, to an exceedingly rare granulomatous phlebitis.
Three forms of lymphocytic vasculitis have been recorded:
(i) concentric lymphohistiocytic infiltrates with lamination of the adventitia by basement membrane material, seen typically in penile lesions;
(ii) lymphocytic vasculitis with dense perivascular lymphocytic cuffing with occasional fibrin deposition in vessel walls and subendothelial infiltration by lymphocytes;
(iii) intramural lymphocytic infiltrates in large muscular vessels.
In the early stages, elastic fibers are pushed downwards by the edematous zone and subsequently destroyed.
Fibrillin is reduced in the upper dermis, but it is normal immediately beneath the basement membrane.
In contrast, elastic fibers are normal or increased in morphea.
Small amounts of acid mucopolysaccharide may be found in this zone. The basement membrane may focally fragment and PAS-positive material may be found in the subjacent dermis, partially as homogeneous clumps.
Numerous invaginations and holes are present in the basement membrane zone (BMZ) at the level of the lamina lucida and lamina densa; in contrast, the continuity of the BMZ is preserved in morphea.
In bullous lesions of LSA, the split occurs below the lamina densa.
- In early lesions, the inflammatory infiltrate is quite heavy and is superficial and band-like, mimicking lichen planus.
- Basal apoptosis and vacuolar change accompany the infiltrate; that is, there are features of the lichenoid tissue reaction (interface dermatitis).
- Overlap syndromes with lichen planus have also been suggested.
- Features favoring a diagnosis of LSA over lichen planus include basilar epidermotropism, basement membrane thickening, epidermal atrophy, loss of papillary dermal elastic fibers, paucity of cytoid bodies, and a lack of wedge-shaped hypergranulosis.
- As the edematous zone broadens, the infiltrate is pushed downwards and becomes more dispersed and usually less intense.
- Changes also involve adnexal structures.
- Lesions of LSA may also mimic mycosis fungoides because of the presence of epidermotropism and focally coarse collagen bundles in the papillary dermis.
- Monoclonal T lymphocytes have also been recorded.
- Incidentally, mycosis fungoides may present clinically with lesions resembling LSA.
- Melanocytic proliferations developing in LSA may show atypical features.
- Melanocytic nevi often resemble persistent melanocytic nevi.
- Melanocytes, nevoid or malignant, proliferating contiguously with fibrotic or sclerotic collagen, contain abundant melanin, diffusely express HMB-45, and have a higher Ki-67 labeling index than ordinary melanocytic nevi.
- In presumptive cases with coexisting morphea, the absence of vacuolar alteration, the lack of a well-defined inflammatory infiltrate beneath the thickened dermis, and the presence of deep dermal changes of morphea are features supporting a diagnosis of morphea without coexisting LSA.
acrochordon and skin tag
- Microscopic features of LSA have been recorded, as an incidental finding, in acrochordons and in the skin tag/folds of the perineum known as infantile pyramidal (perineal) protrusion.
- Another study of this protrusion showed no histological evidence of LSA.
Electron microscopy has shown degeneration and regeneration of superficial dermal collagen, the presence of collagen in intercellular spaces in the epidermis, abnormalities of the basement membrane zone, and condensation of tonofilaments in the basal epidermal cells.