Lichen planus (LP) is a chronic inflammatory dermatosis that primarily affects the skin and mucosal surfaces. It presents with polygonal, pruritic, purple papules and plaques, which can sometimes lead to post-inflammatory hyperpigmentation (1). The disease is histopathologically characterized by a lichenoid tissue reaction pattern, basal cell degeneration, band-like lymphocytic infiltration, and pigment incontinence (2). However, LP exhibits significant histopathological variability depending on its clinical variant, making accurate diagnosis challenging.

The pathogenesis of LP is believed to be immune-mediated, with T-cell-induced apoptosis of basal keratinocytes being a key event (3). The etiology remains unclear, but associations with viral infections, autoimmune diseases, and drug-induced reactions have been reported (4). Different variants of LP, such as hypertrophic LP, lichen planus pigmentosus (LPP), and linear LP, exhibit diverse clinical and histopathological characteristics. While hypertrophic LP is marked by epidermal hyperplasia and hyperkeratosis, LPP is associated with increased pigment incontinence and basal cell degeneration (5,6).

Histopathological evaluation plays a crucial role in confirming the diagnosis of LP and its variants, as clinical differentiation alone can often be misleading. Despite a clear histopathological pattern in most cases, overlapping features with other dermatoses necessitate meticulous examination and clinicopathological correlation (7). Previous studies have reported significant variability in epidermal and dermal features among LP subtypes, further emphasizing the need for comparative histopathological analysis (8,9).

Given the scarcity of literature on the histopathological spectrum of LP variants in the Indian population, this study aims to analyze and compare their microscopic features. The findings are expected to enhance diagnostic accuracy and guide better therapeutic interventions.

Study Design and Setting

This was a descriptive, cross-sectional study conducted in the Department of Pathology at Rajarajeswari Medical College and Hospital (RRMCH), Bengaluru. The study was carried out over a two-year period from June 2015 to May 2017.

Study Population and Sample Size

A total of 100 skin biopsy specimens diagnosed as hyperpigmented skin lesions were analyzed. Among them, 76 cases were classified as non-neoplastic, primarily consisting of LP and its variants. The sample size was determined based on a retrospective analysis of LP cases received in the department over the previous three years.

Inclusion Criteria

• Skin biopsy specimens from patients clinically diagnosed with LP and its variants.
• Cases with adequate biopsy samples for histopathological examination.

Exclusion Criteria

• Patients unwilling to undergo a biopsy procedure.
• Inadequate or autolyzed biopsy specimens.

Data Collection and Histopathological Examination

Biopsy specimens were collected from patients in the dermatology outpatient department. Each specimen was fixed in 10% formalin and processed using standard histopathological techniques. Paraffin-embedded tissue sections of 3–4 µm thickness were prepared and stained with hematoxylin and eosin (H&E) for microscopic examination. Additional special stains, such as periodic acid-Schiff (PAS), were used when necessary.

Histopathological evaluation included assessment of epidermal changes (hyperkeratosis, acanthosis, basal cell degeneration), dermal alterations (pigment incontinence, inflammatory infiltrate), and other characteristic features such as Civatte bodies and colloid degeneration. Each variant was compared based on these histological parameters.

Data Analysis

The histopathological findings were documented and analyzed using descriptive statistics. The frequency and percentage of various histopathological features were calculated and compared among the LP variants. Clinicopathological correlation was established by comparing clinical diagnoses with histopathological findings.

The present study analyzed the histopathological variations in different types of lichen planus (LP) and its variants, focusing on clinical correlation, site distribution, and microscopic features. A total of 100 cases were examined, comprising both non-neoplastic and neoplastic hyperpigmented skin lesions. The study aimed to highlight the variability in histopathological patterns among these cases.

Distribution of Lichen Planus Variants

Among the 100 hyperpigmented skin lesions analyzed, 76 cases (76%) were classified as non-neoplastic, with different LP variants constituting the majority. Classical LP was the most frequent variant, accounting for 35.5% of cases, followed by lichen planus pigmentosus (LPP) (24.0%), hypertrophic LP (16.0%), and linear LP (8.0%). A smaller proportion of cases included lichen striatus, lichen amyloidosis, and atrophic LP (Table 1).

Table 1: Distribution of Lichen Planus Variants (n=76)

Classical LP was the most commonly diagnosed subtype, followed by LPP and hypertrophic LP. The least common subtypes included lichen striatus, lichen amyloidosis, and atrophic LP (Table 1).

Site Distribution of Lichen Planus Variants

The most frequently affected site was the extremities, with 51.3% of cases presenting lesions on the upper and lower limbs. Generalized distribution was seen in 19.7% of cases, while 15.8% of cases were localized to the face and neck. The trunk was involved in 13.2% of cases (Table 2).

Table 2: Site Distribution of Lichen Planus Variants (n=76)

The extremities were the most commonly affected site, with over half of the cases involving the limbs. Generalized involvement was noted in nearly one-fifth of the cases, followed by the face, neck, and trunk (Table 2).

Histopathological Features of Lichen Planus Variants

Microscopic examination of LP and its variants revealed variations in epidermal and dermal involvement. Hyperkeratosis was observed in 78.9% of cases, while acanthosis was noted in 67.1%. Basal cell degeneration was prominent in 52.6% of cases, particularly in classical and pigmentosus LP. Pigment incontinence was seen in 47.3% of cases. Lymphocytic infiltration, a hallmark of LP, was present in 82.9% of cases, with a perivascular distribution in 73.6% (Table 3).

Table 3: Histopathological Features of Lichen Planus Variants (n=76)

Hyperkeratosis and acanthosis were among the most common epidermal changes, while basal cell degeneration and pigment incontinence were prominent in LP variants. Lymphocytic infiltration, particularly with perivascular inflammation, was a key dermal feature (Table 3).

• Classical LP was the most common subtype, followed by LPP and hypertrophic LP (Table 1).
• The extremities were the most frequently involved site, followed by generalized distribution and facial involvement (Table 2).
• Histopathologically, hyperkeratosis, basal cell degeneration, and pigment incontinence were observed across LP variants, with lymphocytic infiltration being the most consistent feature (Table 3).

These findings highlight the histopathological diversity of LP variants and reinforce the importance of clinicopathological correlation for accurate diagnosis and management.

Lichen planus (LP) is a chronic inflammatory disorder of unknown etiology, often affecting the skin and mucosa. Histopathological examination remains crucial for differentiating LP from other hyperpigmented dermatological conditions. This study highlights the histopathological variability in LP and its variants, emphasizing clinical correlation, age and sex distribution, and site predilection.

Our study found that LP and its variants were more prevalent in the third and fourth decades of life, similar to previous studies that reported peak incidence in individuals aged 21–40 years (1,2). A slight female preponderance was observed, with a female-to-male ratio of 1.05:1, aligning with studies that report a marginally higher incidence in females (3,4). The extremities were the most commonly involved site (51.3%), followed by generalized presentation (19.7%) and facial involvement (15.8%). This finding is consistent with prior research highlighting limb predilection in LP (5).

Histopathologically, hyperkeratosis and acanthosis were the most frequently observed epidermal changes, present in 78.9% and 67.1% of cases, respectively. Similar findings have been reported, where these features were predominant in lichenoid tissue reactions (6,7). Basal cell degeneration, a key feature in LP, was seen in 52.6% of cases, particularly in classical LP and lichen planus pigmentosus (LPP). Pigment incontinence, a hallmark of LPP, was noted in 47.3% of cases, comparable to other studies where it ranged between 40%–55% (8,9).

Lymphocytic infiltration was the most consistent dermal feature, seen in 82.9% of cases, with perivascular distribution in 73.6%. This aligns with prior histological studies emphasizing band-like lymphocytic infiltrates as a key diagnostic marker for LP (10,11). The presence of colloid (Civatte) bodies in 11.8% of cases further supports the inflammatory pathogenesis of LP (12).

Among the different LP variants, classical LP was the most frequent subtype (35.5%), followed by LPP (24.0%) and hypertrophic LP (16.0%). These findings are consistent with prior reports where classical LP was predominant, accounting for 25–40% of cases (13,14). LPP, characterized by increased basal layer pigmentation and pigment incontinence, was significantly associated with higher melanophage counts and involvement of sun-exposed areas (15). Hypertrophic LP exhibited marked hyperkeratosis, papillomatosis, and dermal fibrosis, similar to earlier descriptions of its prolonged inflammatory course and dermal remodeling (16).

A strong correlation between clinical and histopathological diagnosis was noted in 94% of cases, supporting the diagnostic reliability of histopathology in LP. This concordance rate is in line with previous studies reporting 92–95% agreement between clinical and histopathological findings in LP and its variants (17,18). However, 6% of cases showed diagnostic discordance, underscoring the overlap of LP with interface dermatitis and other lichenoid reactions such as drug-induced LP and lichenoid keratosis (19).

Histopathology remains the gold standard for diagnosing LP, particularly in cases with atypical presentations. While clinical assessment is essential for initial diagnosis, histopathological confirmation is necessary for differentiating LP from other pigmented dermatoses like post-inflammatory hyperpigmentation, lupus erythematosus, and erythema dyschromicum perstans (20). The variability in epidermal and dermal changes across LP subtypes necessitates detailed microscopic evaluation to ensure accurate classification and management (21).

This study underscores the histopathological diversity of LP and its variants, reaffirming the role of biopsy-based diagnosis in dermatopathology. Hyperkeratosis, acanthosis, basal cell degeneration, and pigment incontinence were consistent findings, with lymphocytic infiltration as a key diagnostic feature. The high clinicopathological concordance (94%) highlights the diagnostic accuracy of histopathology, reinforcing its significance in distinguishing LP from other hyperpigmented skin disorders. Further research with larger cohorts and immunohistochemical studies may help elucidate the pathophysiological basis of histological variations in LP.

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