Clinicopathologic evaluation of granuloma annulare: Study of 136 Iranian cases, south of Iran

Abstract Background and Objectives Granuloma annulare (GA) is a benign skin disorder with various histopathologic features that are rarely investigated in Iranian population. We performed this study to find out the clinical and histopathologic features of GA in our referral centre. Methods One hundred‐thirty‐six patients with biopsy‐proven GA were reviewed. Clinical data and pathological features were recorded. Results One hundred‐eight female patients and 28 male patients (Female/male ratio: 3.85) with mean age of 42.54 ± 21.2 years (range: 2–83 years) were recruited. Eighty‐eight (64.7%) patients had interstitial infiltrative pattern and 48 (35.3%) patients had complete palisading granulomas. The infiltrate occupied both upper and lower dermis in most of the cases (67.7%). Significant mucin was detected more commonly in complete GA compared to interstitial GA (p = 0.019), but inflammation degree, eosinophils, plasma cells, and giant cells were not different between two subtypes of GA (p > 0.05). The significant inflammation contained more significant plasma cells (p = 0.006). The significantly more giant cells were detected in patients between 20 and 60 years of age (p = 0.015); but other factors were not different between age groups. Conclusions In our study, the prevalence of GA in women was significantly higher than in men. Interstitial GA was the more common histological subtype and the inflammation was less severe and the infiltrate was mostly pandermal in our cases. More severe inflammation contained more plasma cells, and more dense giant cells were seen in middle aged patients.


| INTRODUCTION
Granuloma annulare (GA) is a self-limited and benign disease in all age groups.It consists of grouped papules in an enlarging annular shape.It is asymptomatic, however, some cases may have mild pruritus.It might occur anywhere on the body but mostly occurs on the lateral or dorsal surfaces of the hands and feet. 1,27][8] The diagnosis relies on clinicopathological correlation.The histological features of GA include collagen degeneration, palisading granulomas, mucin, and a lymphohistiocytic infiltrate. 9,10In a study conducted by Umbert et al., the most common histological pattern of GA was infiltration of histiocytes -1 of 8 https://doi.org/10.1002/ski2.299 between collagen fibres, with minimal necrobiosis (72%), followed by the palisading granulomas (25%), and the epithelioid nodules (3%).The electron microscopic findings were histiocytes with membrane activity, large mitochondria, numerous lysosomes, and welldeveloped rough endoplasmic reticulum. 11clinical presentation of GA is classified into localized, generalized/disseminated, subcutaneous, and perforating types. 9,12 few studies are present assessing the histological features of GA in Iranian patients; so, we conducted this retrospective, cross-sectional study to evaluate the clinicopathological features of GA in this population.

| Study population
In this retrospective cross-sectional study, we recruited all the biopsy-proven cases of GA by searching the pathology lab file of Shahid Faghihi hospital in Shiraz, Southern Iran, since December 2010 to March 2020.We recorded location of the lesions, demographic features including age, sex, and the clinical differential diagnosis.The pathology slides were reviewed once more with two expert dermatopathologists to determine the subtype of GA and their histologic features.
Inclusion criteria was biopsy-proven GA, and exclusion criteria consisted of unavailable or poor quality pathological slides or specimen that makes the review impossible.

| Data collection
All data regarding patients' sex, age, differential diagnosis, biopsy site, and their histologic features were recorded using SPSS version 26.No and 1þ mucin, eosinophils, and plasma cells were considered as not significant while 2þ and 3þ mucin, eosinophils, and plasma cells were considered as significant.Minimal and mild inflammation were considered as nonsignificant, and moderate and severe inflammation were considered as significant inflammation.Detection of no, rare, and few giant cells were considered as nonsignificant, and detection of some and many giant cells were considered as significant.

| Statistical analysis
All data were analyzed using the chi-square test.Descriptive statistics were reported as frequency (percentage) and analytical statistics were reported as mean � standard deviation.A two-sided p-value of less than 0.05 was considered statistically significant.

| RESULTS
One hundred-forty-nine patients were enroled.Slides of 13 cases could not be retrieved and therefore were excluded from the study.Thus, a total number of 136 patients were evaluated.Female/male ratio was 3.85.Interstitial GA was detected in 88 (64.7%) cases and 48 (35.3%) specimen showed features of complete GA.Clinical and histological characteristics of GA cases are presented in Table 1.
All patients (100%) had some degree of perivascular inflammation.There was no relation between inflammation degree, eosinophil, plasma cell, and giant cell in GA subtypes (p-value >0.05).
The degree of inflammation, eosinophil density, and plasma cell density were not different in different genders (p-value >0.05).

What is already known about this topic?
� Granuloma annulare (GA) is a benign skin disorder with various histopathologic features.� GA is more prevalent in middle-aged and female patients.� Interstitial GA is the more frequent histological type of disease, and mucin is a common finding, especially in the complete type.

What does this study add?
� The intensity of inflammation may be less severe than the previous studies.� More severe inflammation contains more plasma cells � More dense giant cells could be seen in middle aged patients.
More dense plasma cells were related with milder degrees of eosinophil infiltration; however, we detected no significant relation between density of eosinophils and plasma cells (p-value = 0.848).
Mucin density, inflammation degree, eosinophil, and plasma cell density were not significantly different in different age groups (p-value >0.05).Significant plasma cells were mostly seen in the patients older than 60 years of age (50%).However, this difference was not significant (p-value = 0.051).The most significant giant cells (52.5%) were seen in the 20-60 years age group (p-value = 0.015) (Table 4).
T A B L E 1 Clinical and histological characteristics of granuloma annulare patients and specimens.Three cases had neutrophils (� nuclear debris) in the necrobiotic areas (2.2%).Two cases had signs of focal leukocytoclastic vasculitis and deep dermal necrotizing vasculitis (1.5%).Four cases had foci of sarcoidal granuloma (2.9%).
Extremities were the site of predilection in our patients.The most common location of the lesion in women was hand followed by dorsum of feet.While the most common location of the lesion in men was the dorsum of feet followed by hand.These relations were not statistically significant (p-value = 0.63).

| DISCUSSION
Granuloma annulare is a benign, relatively common skin eruption.The clinical subtypes are localized, generalized, subcutaneous, and perforating GA.Although GA can be diagnosed clinically in most of the cases, skin biopsy is used to confirm the diagnosis or in the lesions with atypical presentations.The biopsy can reveal palisading granulomas, collagen degeneration, mucin, and a lymphohistiocytic infiltrate. 9,13,14his study determined the clinical and histopathologic features in patients with GA for the first time in

T A B L E 2 Comparison of different histological features between complete and interstitial type of granuloma annulare.
T A B L E 3 Relation between inflammation degree and degrees of eosinophils and plasma cells inflammation in granuloma annulare specimens.
Iran.According to our study this disease predominantly affected middle-aged persons.GA was more frequent in female compared to male patients and was more seen in extremities in both gender.Interstitial GA was the more common histological subtype, but significant amount of mucin was mostly detected in complete subtype of GA.More severe inflammation contained more plasma cells, and more dense giant cells were seen in middle aged patients.In study of Barbieri et  female was more affected than male (3:1) 15 ; Most prevalent presentation in the 5th and 6th decades of life was also reported in the other studies. 2,16These findings are similar to our research's findings.Female predominance is reported in several studies 2,16,17 that is in concordance with our study.In line with our research, in other studies extremities were the most affected area. 16,18alignancy-associated and childhood GA also presented on the extremities in most patients. 18,19n most of the studies that assessed the histopathologic findings of GA, interstitial pattern was the more common type of GA and 33%-71% of cases demonstrated this pattern. 11,16,17,19,20owever, Cheng et al. 21showed palisading histiocytes as a predominant type of infiltration in GA (63.6%).Also, necrobiotic GA was slightly more than the interstitial and mixed types in the GA cases not associated with malignancy. 180][21] The difference between studies may be the result of detection of mucin in the H&E or mucin special stains.Mucin was detected more frequently in the complete type of GA, compared to the interstitial GA, both in our and previous studies. 11,17Ronen et al. 17 reported scant to absent mucin in the interstitial GA.Despite the more frequent mucin in the complete type, the difference with interstitial type was not significant in our study.Detection of mucin is considered a clue to differentiate GA from other dermatoses with palisading granuloma. 21Mucin was more frequently detected in the Malignancy-associated GA compared to control group. 189][20][21] The possibility of insect bite or drug reactions are proposed as the causes of eosinophil-rich GA (20).Giant cells (43.3%) were less frequent than some of the studies (57%-90%), 16,[18][19][20] but higher than some other studies (15.9%). 21We detected plasma cells in 38.2% of our patients.Plasma cells are reported in few previous studies in 33% of specimen. 16Significant inflammation (30% of our specimen) was less than the similar studies (60%-70%). 16,18Different definition and lack of objective tools to measure the inflammation degree may explain this disconcordance.Neutrophils were more frequent in some studies 20 (33%), compared to our results.Umbert et al. 11 observed polymorphonuclear leukocytes in the necrotic areas, but they were absent in infiltrations.Vasculitis was a prominent feature in some studies (10%-20%), 16,20 but we detected few cases of vasculitis in our GA specimens.
The depth of infiltration is presented in different studies.Chaitra et al. 20 reported the upper and middermal infiltrate in 53% of cases.Another study showed 60% upper and mid-dermal, 10% upper dermal, and 30% pandermal infiltrate. 16The infiltration was reported in different depths of dermis in childhood GA. 19 The infiltrate in our cases was mostly pandermal, followed by upper dermal infiltrate.
In our study, there was no significant correlation between inflammation degree, eosinophil, plasma cell, giant cell and different subtypes of GA.
We note some limitations to our study.First, we didn't have access to the records of associated diseases of patients.Second, we couldn't review the follow-up of patients to find out the result of their treatment.
In conclusion, in our study, the prevalence of GA in women was higher than in men, and mostly located on the extremities.Significant amount of mucin was in favour of complete type of GA.More severe inflammation contained more plasma cells, and more dense giant cells were seen in middle aged patients.The inflammation was less severe and the infiltrate was mostly pandermal in our GA cases.

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al. the disease was more frequent in fifth decade of life and T A B L E 4 Comparison of different histological features in granuloma annulare age group.SARI ASLANI ET AL.