|LETTER TO EDITOR
|Year : 2011 | Volume
| Issue : 1 | Page : 39-40
Postauricular pilar sheath acanthoma
Rupali R Bavikar, Vandana Gaopande, Sanjay D Deshmukh
Department of Pathology, SMT. K. N. Medical College, Pune, Maharashtra, India
|Date of Web Publication||16-Jun-2011|
Rupali R Bavikar
C 505, Siciliaa, B. T. Kawde Road, Ghorpadi, Pune 411 001, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Bavikar RR, Gaopande V, Deshmukh SD. Postauricular pilar sheath acanthoma. Int J Trichol 2011;3:39-40
Pilar sheath acanthoma is an uncommon, benign skin neoplasm not associated with other disorders. This lesion was first described by Mehregan and Brownstein.  The classic location for these lesions is the upper lip, although a few cases have been described at other locations such as lower lip and cheeks.  A pilar sheath acanthoma resembles clinically a comedo, presenting as an asymptomatic, small skin-colored papule or nodule with a central opening.
A 25-year-old male presented with a solitary, asymptomatic nodule in the right postauricular region for 1 year. On clinical examination, a skin-colored nodule 1 cm in diameter was seen with a central opening plugged with keratin. An excision biopsy was performed. Center of the lesion showed a central branching cystic cavity that communicated with surface epidermis. The cavity was lined with stratified squamous epithelium that radiates from the wall of the central cystic cavity into the deeper dermis. The cells were round to polyhedral with peripheral palisading [Figure 1] and [Figure 2].
|Figure 1: A cystic cavity lined by stratified squamous epithelium which is continuous with the surface epithelium ×100|
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The pilar sheath acanthoma is a rare, benign follicular hamartoma commonly affecting middle-aged and elderly individuals. It is characterized by a small, solitary, skin-colored papule situated on the head and neck, particularly around the upper lip. In our case, a 25-year-old male presented with a skin-colored nodule with a central opening in a postauricular region. The lesion shares some features with trichofolliculoma and dilated pore of Winer, so it should be differentiated from these.
In the pilar sheath acanthoma, there is a central sinus containing keratinous material. The sinus is lined by epithelium which is continuous with surface epithelium,  while in trichofolliculoma small hair follicles radiate from the wall of central cystic cavity. The hair follicles are well differentiated in trichofolliculoma as compared to pilar sheath acanthoma in which abortive hair follicles are seen. An outer root sheath, inner root sheath, and trychohyaline granules are commonly seen in secondary follicles of trichofolliculoma, features not seen in pilar sheath acanthoma. The pilar sheath acanthoma do not show hair shafts in the central cavity, also the fibrovascular stroma is absent. A few small cysts within the cyst wall can be seen in pilar sheath acanthoma.
Dilated pore of Winer has central cavity lined by acanthotic epithelium with finger-like projections radiating into the surrounding connective tissue. It also shows the presence of a well-organized stroma and hair follicles and sebaceous glands.
The pilar sheath acanthoma also needs to be distinguished from keratoacanthoma, which has a similar clinical appearance. In contrast to keratoacanthoma, the pilar sheath acanthoma shows no spontaneous regression. 
Neoplasms arising from a infundibular portion of pilar apparatus are tumor of follicular infundibulum, trichilemmoma, inverted follicular keratosis, dilated pore, and pilar sheath acanthoma. All these neoplasms have common histological features, i.e. superficial nature of growth, connection with the epidermis, pore-like opening proliferation of outer sheath epithelium, infundibular keratinisation, and connection with the pilosebaceous structure.
Mehregan and Brownstein  described the pilar sheath acanthoma as being less mature than dilated pore of Winer, but more mature than the tumor of follicular infundibulum.
| References|| |
|1.||Mehregan AH, Brownstein MH. Pilar sheath acanthoma. Arch Dermatol 1978;114:1495-7. |
|2.||Ackerman AB, Viragh PA, Chongchitant N. Pilar sheath acanthoma. In: Ackerman AB, Viragh PA, Chongchinant N, editors. Neoplasn with Follicular Differentiation. Philadelphia: Lea and Febiger; 1993. p. 509-32. |
|3.||Lee JY, Hirsch E. Pilar sheath acanthoma. Arch Dermatol 1987;123:569-70. |
|4.||F. Pilar sheath acanthoma. Hautarzt 1987;38:40-2. |
[Figure 1], [Figure 2]