Study of clinicohistopathological correlation of skin adnexal tumours

Introduction

Appendageal tumours (Appendageal tumours) are neoplasms which differentiate towards or arise from pilosebaceous apparatus, apocrine gland or eccrine sweat gland.^[1] These tumors basically originate from undifferentiated pluripotent stem cells and finally differentiate to specific tumors influenced by genetics, local vascularity, and the microenvironment of the epidermis and dermis. Head and neck region is unique because of its rich distribution of pilosebaceous apparatus, apocrine as well eccrine sweat glands. It has also been previously documented that Appendageal tumours predominate over head and neck area.^[1] Clinical diagnosis of different entity is often difficult, as most of the Appendageal tumours present as asymptomatic papules or nodules. Anatomic location, number and distribution of these lesions provide important clue to clinical diagnosis but histopathology is invaluable in conformation of the diagnosis.^[2]

Majority of these tumours are benign^[3], ^[4] and the malignant ones are usually irregularly shaped, solitary, rapidly growing plaques or nodules that have a tendency to ulcerate. Risk of malignant degeneration varies with individual lesions.^[2] Local recurrence is well recorded but metastases is rare with the exception of the malignant eccrine and apocrine gland derived tumors and sebaceous carcinoma.^[3] However, diagnosing some of these tumors has important implications, as they might be markers for syndromes associated with internal malignancies, such as trichelemmomas in Cowden disease and sebaceous tumors in Muir-Torre syndrome.^[5]

The study aims at determining the frequency profile, and distribution of skin adnexal tumours and association of their distribution with patient’s age and sex.

Materials and Methods

It was a cross-sectional, descriptive study, conducted over a period of 1 year from November 2018 to November 2019. Total numbers of patients attending dermatology OPD were recorded and clinically suspicious cases of Appendageal tumours were evaluated. Histopathological examination was advised in all suspected cases and only those subjects consenting for histopathology were included for the study. Confirmed cases of Appendageal tumours were considered as the finally analyzable subjects.

Results

Among 43586 new patients attending OPD, 64(0.14%) cases of Appendageal tumours were suspected. And 60 underwent histopathological examination. Histopathology was confirmatory in only 42 (70%) cases, with an incidence of 0.096%. In the remaining eighteen patients, histopathology revealed either milia or epidermal cyst or basal cell carcinoma. In our study, 70% of clinically suspicious cases were proved to be of appendageal in origin. The hair follicle tumors constituted the largest group involving 26/42(61.90%), followed by the sweat gland tumors 16/42 (38.09%). The hair follicle tumors are comprised of trichoepithelioma 18/42(42.85%), trichofolliculoma 1/42 (2.38%), pilomatricoma 4/42 (9.52%), and trichilemmal cyst 4/42 (9.52%). The sweat glands tumors are comprised of chondroid syringoma 12/42(28.57%), hidrocystoma 2/42(4.76%) and syringocystadenoma papilliferum 1/42(2.38%) [[Table 1]].

Mean presenting age of our study population was 32.64 years (ranging from 11 to 55 years). Most common site affected was head and neck 31/42(73.80%) followed by trunk 9/42(21%), and upper limb 2/42 (5.20%)[[Table 2]].

Female’s outnumbered (65.21%) males (34.78%) in our study population with the male to female ratio being 1:1.62[[Table 3]].

Discussion

The incidence of Appendageal tumours is very low and only 0.096 % of patients attending the OPD were found to be suffering from Appendageal tumours our study. Skin appendageal tumors differentiate along one or more adnexal line and their overall incidence is low in our Indian population.

Appendageal tumours are classified into 4 types according to their differentiation toward apocrine gland, eccrine gland, sebaceous gland and hair follicle. ^[6]

Importance of diagnosing Appendageal tumours lies in the fact that the presence of Appendageal tumours in some instances may lead to the recognition of a genetic syndrome, like Muir-Torre syndrome associated with sebaceous tumors, Cowden's syndrome with trichilemmomas, etc.^[3] It is currently believed that Appendageal tumours are derived from cells that have the ability to differentiate toward any of the appendages. In many lesions, the differentiation is uniform and the tumor can be recognized and categorized based on its resemblance to a normal appendage or part of it. In other cases, the pluripotent cell may differentiate toward more than one type of appendage giving rise to a tumor that contains element of two or more appendage in varying degrees of maturation.^[3] In our study, though such combined nature was not detected. The clinical appearance of appendageal tumor is mostly non-specific ^[1] and their diagnosis lie firmly in the realm of histopathologists. In the present study, 30% (18 /60) of clinically suspected cases were proved to be non-AT after histopathological examination. Milia were mistaken as syringoma, basal cell carcinoma as desmoplastic trichoepithelioma. Hence, these entities should be kept in mind before making a diagnosis of Appendageal tumours. 

In our study, trichoepithelioma [[Figure 1]a,b ] was the most common hair follicle Appendageal tumours constituting 18/42(42.85%) and were distributed around nose suggesting that trichoepithelioma remains the primary differential diagnosis of Appendageal tumours centered around nose. Trichoepithelioma was found to be multiple and familial only in four cases, while solitary variety was found to be more common than multiple. Other hair follicle Appendageal tumours in our study were trichofolliculoma [[Figure 2]a,b] constituting 1/42 (2.38%), pilomatricoma [[Figure 3]a,b] constituting 4/42 (9.52%), and trichilemmal cyst [[Figure 4]a,b] constituting 4/42 (9.52%).

Among sweat gland tumours chondroid syringoma [[Figure 5]a,b] was the most common Appendageal tumours constituting 12/42(28.57%), hidrocystoma[[Figure 6]a,b] constituting 2/42(4.76%), followed by syringocystadenoma papilliferum [[Figure 7]a,b] constituting 1/42(2.38%).

No sebaceous gland Appendageal tumours were identified in our study. Incidence of benign tumours is more as compared to malignant cases. In our study histopathological features of malignancy was absent in all cases and supports the usual benign course of the Appendageal tumours. In present study, most common tumours were Trichoepithelioma and Syringoma followed by Pilomatricoma and Trichilemmal cyst.^[7], ^[8], ^[9], ^[10], ^[11], ^[12]

To summarize the incidence of benign skin AT’s is more as compared to the malignant ones. Skin adnexal tumours can occur anywhere in the body; however head and neck region constitutes the most common site. Histopathology remains the gold standard for diagnosis of these tumours. The higher incidence among females of any age group than males.

Conflict of Interest

None.

Source of Funding

None.