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| LETTER TO EDITOR |
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| Year : 2013 | Volume
: 5
| Issue : 3 | Page : 163-164 |
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Solitary calcified trichilemmal cyst on forearm
Sahana M Srinivas1, Chavan R Vittal2, Madhavi Naik3, Chethan Nagaraj4
1 Department of Dermatology, Ananya Hospital, Karnataka, India
2 Department of Surgery, Ananya Hospital, Karnataka, India
3 Department of Pathology, St Theresa's Hospital, Bangalore, Karnataka, India
4 Department of Orthopaedics, Ananya Hospital, Karnataka, India
| Date of Web Publication | 22-Jan-2014 |
Correspondence Address:
Sahana M Srinivas
Consultant Dermatologist, Ananya Hospital, Bangalore, Karnataka - 560 010
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0974-7753.125623
How to cite this article:
Srinivas SM, Vittal CR, Naik M, Nagaraj C. Solitary calcified trichilemmal cyst on forearm. Int J Trichol 2013;5:163-4 |
Sir,
Solitary asymptomatic nodule poses a great diagnostic challenge to clinicians as there are numerous clinical and pathological differential diagnoses. Trichilemmal cyst, also known as pilar cyst, is a benign cyst containing keratin and its breakdown products, derived from outer root sheath of hair follicle. [1] They affect 5-10% of the population and are commonly encountered by surgeons. Ninety percent of the cysts occur over the scalp and rarely the face, trunk, groin, and extremities may be involved. We report a case of a 60-year-old female who presented with solitary calcified trichilemmal cyst on flexor aspect of forearm, which is rare site for occurrence of these lesions.
A 60-year-old female presented with asymptomatic swelling on forearm from past 10 years, gradually increasing in size from 2 months. There was slight pain and watery like, nonfoul smelling discharge from the swelling from 2 days. There was no history of preceding trauma. Past history was unremarkable. None of the family members had similar complaints. Cutaneous examination showed single well defined, erythematous, firm, freely mobile, tender nodule measuring 1.5 × 2 cm on the flexor aspect of forearm [Figure 1]. Differential diagnosis of inflamed epidermoid cyst, pyogenic granuloma, xanthoma, and foreign body cyst was considered. Excision biopsy of the nodule revealed acanthotic epidermis and cystic lesion in deep dermis lined by stratified squamous epithelium and filled with homogenous eosinophilic material and few nucleated squamous cells. Calcification was noted at the centre of the cyst [Figure 2] and [Figure 3]. Based on histological findings, a diagnosis of calcified trichilemmal cyst was considered. | Figure 1: Well defined, freely mobile, solitary erythematous nodule on the flexor aspect of forearm
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 | Figure 2: (a) Acanthotic epidermis with deep dermis showing small cystic mass (H and E, ×4) (b) Cystic mass lined by stratified squamous epithelium filled with homogeneous eosinophilic material (H and E, ×10)
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 | Figure 3: (a) Lining epithelium with smaller, deeply staining cells at the base and larger, paler cells at the cyst cavity (b) Foci of calcification at centre of cyst (H and E, ×40)
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Trichilemmal cysts arise from the epithelium of follicular isthmus, where the outer root sheath undergoes a specific form of keratinisation (trichilemmal keratinisation) forming a cyst wall without a granular area. It is usually seen in middle age with female preponderance. Familial cases with an autosomal dominant mode of inheritance have been linked to short arm of chromosome 3. [2] They present as multiple, slow growing, freely mobile, firm, nontender intradermal or subcutaneous nodules on the scalp. Solitary lesions are seen in 30% of cases. They may become tender and inflamed following trauma. Few cases have been reported to occur on finger pulp, vulva, eyelid, intraoral area, extensor aspect of forearm, and gluteal region. [3],[4]
Trichilemmal cysts are almost always benign, although malignant transformation can be seen in 2% cases. It is a spectrum of transformation from benign pilar cyst to a proliferating tumor to malignant proliferating trichilemmal tumor. Histopathologically, the cyst contains homogeneous eosinophilic keratinous material. Foci of calcification may develop. The cell of the lining epithelium gradually increases in size as they approach the cyst cavity, appearing swollen with pale cytoplasm, keratinizing abruptly. It is differentiated from epidermoid cyst by absence of punctum and location. Wide excision is the treatment of choice but recurrences are common. [5]
Knowledge about morphology of different cystic lesion and its behavior is essential to come to diagnosis. Many benign cystic lesions can have unusual presentation and can be clinically misdiagnosed. This case not only highlights the unusual location of trichilemmal cyst but also the importance of doing histopathological examination to come to accurate diagnosis.
 References | |  |
| 1. | McGavran MH, Binnington B. Keratinous cysts of the skin. Identification and differentiation of pilar cysts from epidermal cysts. Arch Dermatol 1966;94:499-508. 
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| 2. | Adya KA, Inamdar AC, Palit A. Multiple firm mobile swellings over the scalp. Int J Trichology 2012;4:98-9.
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| 3. | Ikegami T, Kameyama M, Orikasa H, Yamazaki K. Trichilemmal cyst in the pulp of the index finger: A case report. Hand Surg 2003;8:253-5.
[PUBMED] |
| 4. | Sadath HN, Ramachandra S, Kumar MA, Haritha K. Multicentric calcified trichilemmal cysts with alopecia universalis affecting siblings. Indian J Dermatol Venereol Leprol 2013;79:88-91.
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| 5. | Anolik R, Firoz B, Walters RF, Meehan SA, Tsou HC, Whitlow M, et al. Proliferating trichilemmal cyst with focal calcification. Dermatol Online J 2008;14:25.
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[Figure 1], [Figure 2], [Figure 3]
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