ARTICLE
An otherwise healthy 23 year-old woman was referred to our department
for the onset, four months before, of a non itching, slowly enlarging
papule localised on the dorsal aspect of the right forearm; her familial
and personal history were negative for cutaneous diseases.
Physical examination showed a round, scaly, lilac plaque, measuring
3 cm in diameter (Fig. 1);
the patient had no other skin or mucosal involvement.
The lesion was surgically removed, and histopathological examination
revealed orthokeratotic hyperkeratosis, hypergranulosis and focal vacuolar
degeneration of the basal layer. In the papillary dermis a band-like lymphocytic
infiltrate hugging the epidermis, together with melanophages, were present
(Fig. 2).
What is your diagnosis?
Diagnosis
Solitary plaque with histological features resembling those of lichen
planus: solitary lichen planus-like benign keratosis (SLPLBK).
It is an often misdiagnosed entity contemporaneously described in 1966
by Lumpkin and Helwig [1] under the name of "solitary lichen planus" and
by Shapiro and Ackerman [2] as "solitary lichen planus-like keratosis";
both the authors underlined the histological pattern of lichenoid reaction.
The disease occurs with higher rate in females (m:f = 2:3), with age
ranging between 40 and 80 years. The lesions are usually localised in
a photo-exposed area with a predilection, in decreasing order of frequency,
for face and neck area, the forearms, the shoulders and the chest [3].
Clinically SLPLBK is characterised by a single, small (5-20 mm), reddish-brown
papule or plaque, with well-defined borders and, in many cases, a keratotic
surface. Panizzon et al. were able to distinguish, on the basis
of the features observed in 202 patients, three different morphological
types of LPLK: 1) erythematosquamous type; 2) papulokeratotic type and
3) plaque-like type [3]. The lesion, generally asymptomatic, is most commonly
confused, at the time of the diagnosis, with basal cell carcinoma, senile
keratosis, seborrheic keratosis, nevocellular nevus or Bowen's disease
[4].
A clarifying diagnostic role is played by the histological examination,
which should be done on the entire lesion. In contrast to the different
clinical aspects, SLPLBK shows the typical pattern of lichenoid reaction;
the main epidermal features are hyperkeratosis (with focal parakeratosis),
hypergranulosis, irregular acanthosis and vacuolar degeneration of the
basal layer keratinocytes, with exocytosis of lymphoid cells. In the papillary
dermis there is a band-like lympho-histiocytic inflammatory cell infiltrate,
which tends to hug the epidermis; solar elastosis, edematous papillary
layer and lentigo senilis-like changes are also regularly present in variable
degree. More rarely, the presence of hyaline bodies of Civatte and, in
the dermal infiltrate, of plasma cells and eosinophils, together with
melanophages, has been described. No cellular atypia has been reported.
Immunopathological investigation reveals no specific depositions of immunoglobulins,
complement and fibrinogen into the dermo-epidermal junction [1-5].
Because of the similar histological features, some authors have suggested
that SLPLBK may be a forme fruste of lichen planus (LP) [1]. This
hypothesis cannot be supported for the evident clinical differences concerning
both the elementary lesion and the multiple sites of localisation of the
papules in lichen planus. Moreover, no cases of development of generalized
LP in patients with a single lesion of SLPLBK have been reported in the
literature.
The pathogenesis is still obscure. Many studies have reported the frequent
clinical association of SLPLBK with actinic lentigo and senile keratosis
in sun-exposed areas [6, 7]; such correlation is confirmed by the histological
findings of lentigo senilis features, often present at the periphery of
the lichenoid infiltrate [8, 9]. On this basis, some authors conclude
that SLPLBK could be an inflammatory reaction of delayed hypersensitivity
against a preexisting cutaneous lesion [8, 10]. Further evidence in support
of this theory, seems to be the documented evolution of a solar lentigo
into a SLPLBK lesion [11]. On the other hand, the occurrence of SLPLBK
even in non sun exposed areas and the absence of histological evidence
of solar damage in the dermis, reported in a large series of patients
affected by SLPLBK [4], gives evidence against the hypothetical central
role of actinic factors in inducing the lichenoid reaction.
In our patient, the clinical aspect, the site of localisation and the
histological features strongly suggest a diagnosis of SLPLBK; the young
age of onset and the absence, both clinically and histologically, of signs
of actinic damage point out the multifactorial pathogenesis of the disease,
in which the lichenoid reaction is problably the result of an immuno-mediate
response to various types of unknown stimuli.
References
1. Lumpkin LR, Helwig EB. Solitary lichen planus. Arch Dermatol
1966; 93: 54-5.
2. Shapiro L, Ackerman AB. Solitary lichen planus-like keratosis.
Dermatologica 1966; 132: 386-92.
3. Panizzon R, Skaria A. Solitary lichenoid benign keratosis:
a clinicopathological investigation and comparison to lichen planus. Dermatologica
1990; 181: 284-8.
4. Scott MA, Johnson WC. Lichenoid benign keratosis. J Cutan
Pathol 1976; 3: 217.
5. Le Coz CJ. Kératose lichenoide solitaire. Ann Dermatol
Venereol 2000; 127: 219-22.
6. Laur WE, Posey RE, Walzer JD. Lichen planus-like keratosis.
J Am Acad Dermatol 1981; 4: 329-36.
7. Glaun RS, Dutta B, Helm KF. A proposed new classification
system for lichenoid keratosis. J Am Acad Dermatol 1996; 35: 772-4.
8. Mehregan AH. Lentigo senilis and its evolution. J Invest
Dermatol 1975; 65: 429.
9. Prieto VG, Casal M, McNutt NS. Lichen planus-like keratosis:
a clinical and histological re-examination. Am J Surg Pathol 1993;
17: 259-63.
10. Berman A, Herszenson S, Winkelmann RK. The involuting lichenoid
plaque. Arch Dermatol 1982; 118: 93-6.
11. Goldenhersh MA, Barnhill RL, Rosenbaum HM, Stenn KS. Documented
evolution of a solar lentigo into a solitary lichen planus-like keratosis.
J Cutan Pathol 1986; 13: 308-11.
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