Are You Confident of the Diagnosis?
Characteristic findings on physical examination
Lichenoid keratosis (LK) is a common benign skin growth that typically presents as an evolving single discrete papule on the trunk or upper extremities of adults (Figure 1). LK occurs almost always as a solitary skin growth; however, two or three lesions can occasionally be present. Approximately 8% of patients with LK will have two discrete lesions, 1% with three; more than three lesions are exceedingly rare.
LK can range in size from 3 to 20mm in diameter and have a myriad of variations in color. Pink to red is most common, but some may be pigmented slightly brown (Figure 2) Lichenoid keratoses may be smooth, scaly or verrucous in appearance.
The dermatoscopic features of lichenoid keratoses vary based on the stage of the lesion and nature of the underlying growth. They are typically a reddish-brown color with a localized or diffuse brownish-grey granular pattern.
Clinically, lichenoid keratoses are most often diagnosed as either an inflamed seborrheic keratosis or a basal cell carcinoma. Other lesions that mimic LK are Bowen’s disease, inflamed lentigines, and actinic keratoses. The clinical distinction can be nearly impossible and pathological evaluation is required to reliably make this diagnosis.
Expected results of diagnostic studies
Histopathologic analysis will show a pronounced lichenoid inflammatory infiltrate that is nearly identical to that seen in lichen planus. The epidermis often shows apoptotic keratinocytes, epidermal acanthosis, hypergranulosis, and hyperkeratosis. Some histologic features that may be present to differentiate lichenoid keratosis from lichen planus include parakeratosis and an inflammatory infiltrate containing scattered eosinophils and plasma cells. All these findings may be seen in conjunction with an abutting epidermal focus of a lentigo (Figure 3).
It is important to understand that melanoma in situ with a lichenoid regression pattern may histologically mimic a lichenoid keratosis. It is also very important to know that nearly any histologically lichenoid process may simulate a lichenoid keratosis including lichen planus, cutaneous lupus and mycosis fungoides. In these cases it is critically important that the clinical history submitted to the pathologist is complete and accurate.
As an example, in some cases histologic evaluation of a lichenoid keratosis can not distinguish between an LK and lichen planus. Only with the appropriate historical information can the pathologist make a definitive diagnosis.
No serologic, genetic or imaging studies are required to make the diagnosis of LK. This is a clinical pathological diagnosis.
Who is at Risk for Developing this Disease?
LK occurs in adults, generally starting in the fourth decade of life with most cases presenting in the fifth to sixth decades of life. For reasons unknown, LKs are three times as frequently encountered in females than males. In addition, this growth is seen most frequently in the Caucasian population.
What is the Cause of the Disease?
The pathophysiology is thought to be due to a chronic inflammatory-mediated involution of a pre-existing epidermal lesion. The inflammatory reaction is thought to be a type of cell-mediated immune rejection of the overlying epidermal growth. The inciting stimulus for this inflammatory reaction is unknown. The epidermal growths that are most commonly considered to be the precursor lesion of the LK include solar lentigines and seborrheic keratoses. Reports of large cell acanthomas and viral warts have also been implicated.
Systemic Implications and Complications
There are no systemic implications. One must be certain to evaluate an individual with multiple lichenoid keratoses for the diagnosis of lichen planus. Lichenoid keratoses are not believed to have potential for malignant transformation.
Therapeutic options for LK are summarized in the Table I.
|Symptomatic treatment can be obtained with any strength topical corticosteroid||Punch biopsy||Cryotherapy|
|Symptomatic treatment can be attempted with topical antipruritics such as pramoxine and diphenhydramine||Shave biopsy||Curettage, cautery can be used to stop bleeding. It should not be used to dessicate the entire base of the removed LK.|
Optimal Therapeutic Approach for this Disease
There are two main approaches to management based on the certainty of the clinical diagnosis.
First, if the diagnosis is not 100% clear clinically, a biopsy is absolutely necessary. If the biopsy reveals an LK, the patient should be informed of the benign nature of the lesion. If the biopsy did not remove the lesion in its entirety, various destructive modalities may be used to remove the lesion. The best and easiest method is liquid nitrogen cryotherapy. Cryotherapy followed by a light curettage is another reasonable approach, as is a light curettage after anesthetizing the area. The use of cautery is not needed in these cases, but can be added for hemostasis.
Observation is another completely appropriate option. If the patient is not bothered by the lesion, and the clinician is 100% confident in the diagnosis, this is a reasonable option.
If one is certain of the diagnosis clinically, based on the clinical and dermatoscopic features, one can perform cryotherapy or curettage. If the lesion persists it must be biopsied at a follow-up appointment to make certain of the diagnosis.
The most common symptom LK causes patients is itching and a slight tenderness or irritation. Itching can be treated with topical corticosteroids. Most any topical corticosteroid will help, and I start with either 2.5% hydrocortisone cream applied twice a day or triamcinolone 0.1% cream applied twice a day. The corticosteroids for the most part only help with the itching and somewhat with the redness. They are not helpful for tenderness.
Patients should be followed for resolution of the LK over time. I usually have patients call me if the lesion has not resolved after cryotherapy. In these cases I will have them return for a therapeutic shave biopsy to attempt to remove the entire lesion, for diagnostic and therapeutic purposes.
If the patient begins to develop multiple lesions, one must reconsider the diagnosis of lichen planus, especially if the areas of involvement include the flexures, mucous membranes, and if there are nail findings. Lichenoid keratoses do not affect the nail bed or mucous membranes.
Unusual Clinical Scenarios to Consider in Patient Management
There are important scenarios to consider regarding LK, which emphasize the importance of clinical-pathological correlation in making the correct diagnosis.
The first scenario to consider is when a portion of a larger pigmented lesion is biopsied, and the pathology report returns as an LK. In certain instances this could be a misdiagnosis due to sampling error or the fact that some melanocytic lesions with lichenoid regression may mimic LK histologically. This may occur in melanoma in which a lichenoid tissue reaction may destroy or obscure nests of melanocytes in portions of the lesions. If the biopsy report results of an LK do not match the pre-biopsy clinical history and physical appearance, one must consider a repeat biopsy.
The next unusual case to consider is when the clinical appearance is of an LK or other lichenoid dermatosis and the pathology report comes back as melanoma in situ or invasive melanoma. In the context of chronic sun-damaged skin with an underlying lichenoid tissue reaction, the presence of increased melanocytes and pseudo-melanocytic nests that may stain positive for Melan-A may lead to a misdiagnosis of melanoma. This point stresses the importance of clinical history and description, as well as the need for a dermatopathologist. An S-100 stain should be used to help differentiate whether these nests are melanocytic cells.
The third issue is the difficulty in some instances of histologically distinguishing LK from lichen planus. Some key histologic features to take note of are a variable number of plasma cells, eosinophils, and neutrophils present in LK. Also, LK displays parakeratosis, which is typically not present in lichen planus. Clinical-pathological correlation is always necessary and is the most sensitive and specific method for differentiating the lichenoid keratosis from lichen planus. Patients with lichenoid keratoses will not exhibit any mucosal lesions, nail findings, or involvement of the hair folliciles as sometimes seen in lichen planus. Lichenoid keratoses are solitary to few in nature whereas lichen planus nearly always has multiple areas of involvement.
The last unusual scenario to be aware of is that LK can histologically mimic other types of lichenoid dermatoses. For example, an early cutaneous lesion of lupus erythematosus (LE) may be misinterpreted as an LK, and vice versa. Also, it has been reported that there can be mycosis fungoides-like histologic patterns of lichenoid keratosis. In any lesion with a lichenoid infiltrate, clinical pathological correlation is necessary to distinguish LK from other entities.
In fact the above scenarios of LK have led to one communication to state that LK should be classified as 1) associated with epithelial changes, 2) associated with melanocytic changes, and 3) miscellaneous (lichen planus, drug eruption, cutaneous lupus, and mycosis fungoides).
What is the Evidence?
Abdulla, F, Mutasim, D. ” Multiple lichenoid keratosis”. J Am Acad Dermatol. vol. 62. 2010. pp. 900-1. (A discussion of a case of a patient with multiple lichenoid keratoses.)
Al-Hiqail, IA, Crawford, RI. ” Benign lichenoid keratosis with histological features of mycosis fungoides: clinicopathological description of a clinically significant histological pattern”. J Cutan Pathol. vol. 29. 2002. pp. 291-4. (Fifteen cases are described in which a mycosis fungoides-like pattern of lichenoid keratoses was observed.)
Beltraminelli, H, Shabrawi-Caelen, LE, Kerl, H, Cerroni, L. “Melan-A-Positive “pseudomelanocytic nests": a pitfall in the histopathological and immunohistochemical diagnosis of pigmented lesions on sun-damaged skin”. Am J Dermatopathol . vol. 31. 2009. pp. 305-8. (A discussion of cases in which lichenoid keratosis was clinically suspected and present; however, a misdiagnosis of melanoma was made.)
Bugatii, L, Filosa, G. ” Dermoscopy of lichen planus-like keratosis: a model of inflammatory regression”. J Eur Acad Dermatol Venereol . vol. 21. 2007. pp. 1392-7. (A discussion of the correlation among clinical, histologic and dermoscopic aspects of lichen planus-like keratosis according to stage of inflammatory regression.)
Dalton, SR, Fillman, EP, Altman, CE, Gardner, TL, Davis, TL, Bastian, BC. ” Atypical junctional melanocytic proliferations in benign lichenoid keratosis”. Human Pathology . vol. 34. 2003. pp. 706-9. (A review of cases involving biopsies of larger pigmented lesions that had a lichenoid keratosis-like histologic appearance.)
Miteva, M, Ziemer, M. “Lichenoid keratosis—a clinicopathological entity with lupus erythematous-like features?”. J Cutan Pathol. vol. 34. 2007. pp. 209-10. (A case is described that clinically appeared as a lichenoid keratosis that turned out to be an early lesion of cutaneous lupus erythematosus.)
Morgan, MB, Stevens, G, Switlyk, S. ” Benign lichenoid keratosis: A clinical and pathological reappraisal of 1040 cases”. Am J Dermatopathol . vol. 27. 2005. pp. 387-92. (A review of the epidemiologic, clinical, and pathological features of 1040 cases of lichenoid keratoses. The most complete review available.)
Prieto, V, Casal, M, McNutt, NS. ” Lichen planus-like keratosis: a clinical and histological reexamination”. Am J Surg Pathol. vol. 17. 1993. pp. 259-63. (A clinical and histologic review of 100 cases of lichen planus-like keratosis.)
Russel, SG, Dutta, B, Helm, K. ” A proposed new classification system for lichenoid keratosis”. J Am Acad Dermatol. vol. 35. 1996. pp. 772-4. (A proposed classification system for lichenoid keratosis is outlined with the authors reasoning behind the need for such a classification.)
Weedon, D. Lichen planus-like keratosis. Weedon's skin pathology. 2002. pp. 47-8. (An outstanding review of the histopathology of lichenoid keratoses, as well as a brief clinical background description of lichen planus-like keratosis. )
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