|Year : 2000 | Volume
| Issue : 3 | Page : 149-150
Proliferating Trichilemmal Cyst Mimicking Squamous Cell Carcinoma
Prakash Kumar, KR Chatura, Rekha M Haravi, Chandra
Source of Support: None, Conflict of Interest: None
A proliferating trichilemmal cyst of long standing duration, with its sudden increase in size and ulceration was clinically suspected to be a squamous cell carcinoma. Microscopic features revealed the appropriate diagnosis.
Keywords: Proliferating trichilemmal cyst, Squamous cell carcinoma
|How to cite this article:|
Kumar P, Chatura K R, Haravi RM, Chandra. Proliferating Trichilemmal Cyst Mimicking Squamous Cell Carcinoma. Indian J Dermatol Venereol Leprol 2000;66:149-50
|How to cite this URL:|
Kumar P, Chatura K R, Haravi RM, Chandra. Proliferating Trichilemmal Cyst Mimicking Squamous Cell Carcinoma. Indian J Dermatol Venereol Leprol [serial online] 2000 [cited 2019 Jun 17];66:149-50. Available from: http://www.ijdvl.com/text.asp?2000/66/3/149/4904
| Introduction|| |
Proliferating trichilemmal cyst also known as pilar tumour, is a benign adnexal tumour of skin, related to the isthmus of the hair follicle.  Proliferating trichilemmal cyst may be misinterpreted histologically as squamous cell carcinoma because of cellular atypia, occasionally seen in this benign tumour. 
| Case Report|| |
A scalp swelling of 20 years duration with sudden increase in size and ulceration over the past 3 months was the presenting sympton in a 75-yearold man. Clinically squamous cell carcinoma was considered in the differential diagnosis. An edge biopsy was done for further evaluation.
Histopathology showed a well delineated lesion composed of lobules of squamous epithelial cells with central trichilemmal keratinisation and calcification [Figure - 1] Squamous pearls, individual cell keratinisation, squamous cells with pleomorphic nuclei suggestive of cellular atypia and increased mitotic activity were also noted, which at first glance suggests a squamous cell carcinoma.
| Discussion|| |
Proliferating trichilemmal cyst, more commonly known as pilar tumour, is almost always found on the scalp of elderly females.  The lesion may grow into a large, elevated, lobulated mass that may undergo ulceration and thus greatly resemble squamous cell carcinoma. 
They are viewed as a complication of ordinary pilar cysts due to chronic irritation caused by the retained secretion, with trauma and inflammation acting as probable adjuvant factors. 
The sudden increase in size and ulceration of a long standing swelling prompted a diagnosis of squamous cell carcinoma in our case. Despite an aggressive histologic appearance of these lesions, majority of them follow a benign course.  Individual histologic fields taken out of context may be frequently difficult to differentiate from squamous cell carcinoma. Areas of cellular atypia are often seen. Features in favour of proliferating trichilemmal cyst are sharp circumscription from surrounding stroma, trichilemmal keratinisation and calcification. 
The diagnosis of carcinoma arising in a proliferating pilar cyst should be made with caution. Infiltration of adjacent structures and/or evidence of metastasis are hallmarks of carcinomatous transformation. 
Our case emphasizes the necessity for detailed clinical and pathological correlation to reveal the diagnosis.
| References|| |
|1.||Massa MC, Medenica M. Cutaneous adnexal tumours and cysts: Part 1. Pathol Ann 1985; 189-233. |
|2.||Brownstein MH, Arluk DJ. Proliferating trichilemmal cyst: A simulant of squamous cell carcinoma. Cancer 1981; 48: 1207-1214. [PUBMED] |
|3.||Amaral ALM, Nascimento AG, Goellner JR: Proliferating pilar (trichilemmal) cyst. Arch Pathol Lab Med 1984; 108: 808-810. |
[Figure - 1]