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  Table of Contents    
CASE REPORT  
Year : 2013  |  Volume : 56  |  Issue : 4  |  Page : 437-439
Cystic panfolliculoma of the scalp: Report of a very rare case and brief review


Department of Pathology, College of Medicine, King Saud University, Riyadh, Saudi Arabia

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Date of Web Publication18-Jan-2014
 

   Abstract 

Panfolliculoma is an exceeding rare follicular benign neoplasm with differentiation toward both upper and lower segments of the hair follicle. In this report, we present a case of cystic panfolliculoma in the occipital region of the scalp of a 19-year-old female. We describe the histopathological and immunohistochemical features of the tumor and briefly discuss the differential diagnoses of this rare entity.

Keywords: Panfolliculoma, skin adnexal tumors, skin cysts

How to cite this article:
Alkhalidi HS, Alhumaidy AA. Cystic panfolliculoma of the scalp: Report of a very rare case and brief review. Indian J Pathol Microbiol 2013;56:437-9

How to cite this URL:
Alkhalidi HS, Alhumaidy AA. Cystic panfolliculoma of the scalp: Report of a very rare case and brief review. Indian J Pathol Microbiol [serial online] 2013 [cited 2020 Jan 27];56:437-9. Available from: http://www.ijpmonline.org/text.asp?2013/56/4/437/125363



   Introduction Top


Histopathological examination of the hair follicle neoplasms usually enables the identification of the predominant type and pattern of follicular differentiation that a particular tumor is following. Based on this fact, follicular neoplasms can be classified according to the part or segment of the hair follicle that the lesion is differentiating into or most closely resemble. However, when differentiation toward the entirety of the hair follicle occurs, the term panfolliculoma is used to designate such neoplasms. [1]

We report a case of panfolliculoma that exhibits an unusual and rarely described cystic pattern. The histopathological characteristics are described with special emphasis on the criteria used to differentiate this rare lesion from other follicular tumors, which may show slightly similar appearances.


   Case Report Top


This was a case report of a 19-year-old female patient who noticed a swelling on her scalp for about 2 years. Examination revealed a dome-shaped, slightly erythematous nodule that was located on her occipital area and measured 0.9 cm × 0.8 cm. The lesion was initially asymptomatic, but gradually became mildly painful. The clinical differential diagnoses included a pilar cyst and lipoma. The nodule was completely excised and submitted for histopathological examination.

Scanning magnification revealed a cyst wall lined by stratified squamous epithelium with underlying hair follicles-like structures and surrounding lobules of basaloid cells [Figure 1]. The cyst extended to the deep dermis. Structures that resembled the different hair follicle elements were also represented in the wall of the cyst. Some of these components are noted in a single medium power field [Figure 2]. These included infundibular component, which was represented by stratified squamous epithelium with deeply basophilic cytoplasmic keratohyaline granules. Features of an isthmus differentiation were also seen as scattered clusters of sebaceous cells and small ducts in the wall of the cyst. More toward the center of the cyst, keratin without keratohyalin granules was seen filling the lumen. This was also indicative of isthmus differentiation. The outer root sheet was presented by few clear cell layers forming a cuff surrounding cells with eosinophilic trichohyaline granules. The latter cells represented a matriceal (inner root sheet) component [Figure 3]. The basaloid aggregations at the wall edges exhibited peripheral palisading without clefting. Such pattern represented germ cell derivation [Figure 4]a. The adjacent component of the stroma was prominently fibrocellular. Periodic acid-Schiff and periodic-acid Schiff diastase highlighted the glycogen component of the clear cytoplasm of the outer root sheath cells. High molecular weight cytokeratin was diffusely and strongly positive throughout the different component of the lesion. Cytokeratin 20 revealed scattered Merkel cells in the follicular epithelium [Figure 5]. Ber-EP4 was expressed in the germinal components which also expressed prominent proliferative activity as revealed by Ki-67 [Figure 4]b and c]. Low molecular weight keratin was predominantly negative apart from focal weak activity in the germinal component [Figure 4]d. Overall, the features seen were those of a cystic panfolliculoma.
Figure 1: Low power view that reveals a cysti cally dilated space with att ached basaloid lobules. The cyst lumen is fi lled by lamellated and compact kerati n (H and E, original magnifi cati on: ×25)

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Figure 2: In this single fi eld, diff erent lines of diff erenti ati on in this panfolliculaoma are expressed. These include infundibular with basophilic keratohyaline granules (single thin black arrow), isthmic with sebaceous cells and duct component (single thick black arrow), trichilemmal with clear cells (double white arrow), hair germ cell (double black arrow) and matriceal (single white arrow) diff erenti ati on, (H and E, original magnifi cati on: ×100)

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Figure 3: Eosinophilic trichohyaline granules are present focally within the lining squamous cells cytoplasm, indicati ng matriceal (inner root sheet) diff erenti ati on (H and E, original magnifi cati on: ×400)

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Figure 4: (a) A focus expressing germ cell component, with basaloid lobular patt ern, and surrounding cellular stroma (H and E, original magnifi cati on: ×200). (b and c) Ber-EP4 and Ki-67 expression by the
germinal component, respecti vely (original magnifi cati on: ×200). (d) Low molecular weight Kerati n was focally expressed by the germinal epithelium (original magnifi cati on: ×200)


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Figure 5: Cytokerati n 20 highlighti ng scatt ered Merkel cells in the follicular epithelium (original magnifi cati on: ×200)

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   Discussion Top


There is no universally accepted classification of the hair follicle tumors. Each specific follicular tumor differentiates toward a hair follicle component. The upper components of the hair follicles include the infundibulum and isthmus. Classic examples on such tumors are dilated pore of Winer and pilar sheath acanthoma, respectively. The lower components include matriceal cells (inner root sheath cells), which can give rise to pilomatricoma while the trichilemmal cells (outer root sheet cells) differentiate to trichilemmoma. Germ cell derived tumor is usually represented by trichoblastoma and trichoepithelioma.

Panfolliculoma is a distinctive and extremely rare benign follicular neoplasm. It shows the germinative, the matriceal (trichohyaline granules) and the outer sheath (clear cells) differentiation. Moreover, these tumors can show shadow cells that are suggestive of the hair follicle ostium differentiation and corneocytes in a basket weave and laminated array, resembling infundibular differentiation. This differentiation toward all elements of a hair follicle is unique and differs from other benign follicular tumors. [1]

Panfolliculoma affects both sexes equally. The ages affected mostly lie between the second and seventh decades. It is usually seen on the eyebrow, buttock, trunk, or scalp. The classic presentation of this tumor is a slow growing nodule, which may clinically mimic a basal cell carcinoma. [2],[3]

The histological differential diagnoses of cystic panfolliculoma include dilated pore of Winer, epidermal inclusion cyst, pilar cyst, trichofolliculoma, cystic trichoblastoma and basal cell carcinoma. Dilated pore of Winer has a cystic opening that is lined by an outer root sheet epithelium in which there is infundibular keratinization with the formation of keratohyaline granules. The epithelium shows finger-like projections that radiate to the surrounding dermis. Epidermal inclusion cysts are stratified squamous epithelium-lined cysts with a granular layer near the lumen and lamellar-type keratin while the slightly similar pilar cysts lack such granular cell layer and show non-laminated keratin.

Trichofolliculoma is a relatively common benign follicular tumor characterized by a cystic structure with secondary follicular differentiation of the cyst wall and the formation of small vellus hair shafts inserted into the cystic cavity. It shows mature hair follicle differentiation without proliferation of immature basaloid tumor cells. [4]

Panfolliculoma may also resemble trichoblastoma, especially when examined at lower microscopic magnifications. However, trichoblastoma has greater tendencies toward follicular germs and hair papillae formation and shows no differentiation toward infundibulum, isthmus, outer root sheath, or hair shaft formation. [5] Basal cell carcinoma can mimic panfolliculoma as it exhibits a variety of patterns and differentiation. These include squamous, sebaceous, trichilemmal and other patterns. Panfolliculoma is, however, characterized by the well-demarcated edges and the lack of clefts around the basaloid component. The latter feature is characteristic of basal cell carcinoma. In addition, panfolliculoma contains scattered CK20-positieve Merkel cells, which are absent in basal cell carcinoma.

In summary, panfolliculoma is a distinctive and unusual benign follicular neoplasm that should be differentiated from other neoplastic and basaloid lesions including basal cell carcinoma. It has been suggested that the development of different follicular components in these tumors can be affected by the perifollicular stroma. [6] The tumor differentiates toward all components of the hair follicle, including the upper and the lower segments. Cystic change in panfolliculoma is a rare phenomenon, which is seldom reported in the literature.

 
   References Top

1.Ackerman AB, de Viragh PA, Chongchitnant N. Neoplasms with Follicular Differentiation. London, England: Lea & Febiger; 1993.  Back to cited text no. 1
    
2.Ho C, LeBoit PE, McCalmont TH. Cystic trichoblastomas and panfolliculomas: a new variation in follicular neoplasms. J Cutan Pathol 1995;22:66.  Back to cited text no. 2
    
3.Hoang MP, Levenson BM. Cystic panfolliculoma. Arch Pathol Lab Med 2006;130:389-92.  Back to cited text no. 3
    
4.Headington JT. Tumors of the hair follicle. A review. Am J Pathol 1976;85:479-514.  Back to cited text no. 4
    
5.LeBoit PE. Trichoblastoma, basal cell carcinoma, and follicular differentiation: What should we trust? Am J Dermatopathol 2003;25:260-3.  Back to cited text no. 5
    
6.Wu YH. Folliculosebaceous cystic hamartoma or trichofolliculoma? A spectrum of hamartomatous changes inducted by perifollicular stroma in the follicular epithelium. J Cutan Pathol 2008;35:843-8.  Back to cited text no. 6
    

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Correspondence Address:
Hisham Mohammed Said Alkhalidi
Department of Pathology, College of Medicine, King Saud University, P.O. Box: 325313, Riyadh 11371
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.125363

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

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