|Year : 2014 | Volume
| Issue : 2 | Page : 111-113
An interesting case report of ulcerated proliferating pilar tumor (PPT) mimicking squamous cell carcinoma
Ramesh Uppada, Sudhasmita Rout, Neelima Bora, Ramalakshmi VB Pullela
Department of Pathology, Maharaja Institute of Medical Sciences, Nellimarla, Vizianagaram, Andhra Pradesh, India
|Date of Web Publication||20-Jun-2014|
Assistant professor, Maharaja Institute of Medical Sciences, Nellimarla, Vizianagaram, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Proliferating pilar tumor (PPT) is a rare neoplasm arising from the isthmus of the outer root sheath of the hair follicle, commonly called a proliferating trichilemmal cyst. It is described as a well-circumscribed dermal or subcutaneous neoplasm with squamoid cytologic features and trichilemmal type of keratinization. PPTs most commonly occur on the scalp during the 4 th -8 th decades of life with distinct predilection for women. They typically undergo slow but progressive enlargement over several months to years, yielding lobulated and exophytic masses that occasionally ulcerate mimicking squamous cell carcinoma both grossly and microscopically; posing a diagnostic challenge to young surgeons, dermatologists, and pathologists. Here we report an interesting case of an ulcerated PPT which was diagnosed cytologically as benign adnexal tumor and confirmed histopathologically as benign PPT. Ulcerated PPT is an important differential diagnosis of ulcerated scalp swellings and needs to be differentiated from squamous cell carcinoma.
Keywords: Squamous cell carcinoma, ulcerated proliferating pilar tumor, exophytic mass
|How to cite this article:|
Uppada R, Rout S, Bora N, Pullela RV. An interesting case report of ulcerated proliferating pilar tumor (PPT) mimicking squamous cell carcinoma. J NTR Univ Health Sci 2014;3:111-3
|How to cite this URL:|
Uppada R, Rout S, Bora N, Pullela RV. An interesting case report of ulcerated proliferating pilar tumor (PPT) mimicking squamous cell carcinoma. J NTR Univ Health Sci [serial online] 2014 [cited 2020 Apr 2];3:111-3. Available from: http://www.jdrntruhs.org/text.asp?2014/3/2/111/134858
| Introduction|| |
A proliferating pilar tumor (PPT) is a rare neoplasm arising from the isthmus of the outer root sheath of the hair follicle, commonly called as proliferating trichilemmal cyst and was first described by Jones  in 1966. It is a well-circumscribed dermal or subcutaneous neoplasm with squamoid cytologic features and trichilemmal type of keratinization.  Most tumors arise within a preexisting pilar cyst. PPTs most commonly occur on the scalp during the 4 th -8 th decades of life with distinct predilection for women.  They typically undergo slow but progressive enlargement over several months to years, yielding lobulated and exophytic masses that occasionally ulcerate.  These ulcerated PPTs can greatly resemble squamous cell carcinoma both clinically and microscopically posing a diagnostic challenge to young surgeons, dermatologists, and pathologists. PPTs can undergo neoplastic transformation to malignant PPTs. ,, Here we report a case of an ulcerated PPT which was diagnosed cytologically as benign adnexal tumor and confirmed histopathologically as benign PPT.
| Case report|| |
A 45-year-old female presented with a swelling over right parietal region of scalp for last 1.5 year duration. On examination, swelling was measuring about 3.5 × 3 cm with ulcerated surface that was bleeding on touch and cystic to firm in consistency.
Fine needle aspiration cytology (FNAC) was done from the scalp swelling. The smears were moderately cellular with presence of keratinous material, both anucleate and nucleated squamous cells without any significant cytological atypia [Figure 1]. A diagnosis of benign adnexal neoplasm, probably of pilar origin was given.
|Figure 1: Cytology smears showing blotchy keratinous material in the aspirate (H and E, 400×). Mature nucleate squames and also anucleate squames seen in other parts of the slide|
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On gross examination, the tumor was a hairy, skin covered nodular mass of size 3.5 × 3 × 1.5 cm with surface ulceration. The cut surface was showing a well-circumscribed, lobulated, greyish white mass [Figure 2].
|Figure 2: Cut-section of the ulcerated tumor shows a wellcircumscribed, lobulated, greyish white mass in the dermis|
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Histopathological examination showed surface epidermis with ulceration, acanthosis, and lymphocytic infiltration. A well-demarcated, lobulated mass was present in the lower dermis [Figure 3]. The mass consisted of palisading peripheral cell layer with central squamous cells showing abrupt trichilemmal type of keratinization, forming extensive glassy keratinous material. There are also cystic spaces lined by squamous cells and vacuolated cells, filled with keratinous material resembling squamous pearls [Figure 4]. Focal calcification within keratinous material is seen.
|Figure 3: Shows a well-capsulated nodule in the dermis made up of squamoid cells arranged in lobular and diffuse pattern (hematoxylin and eosin (H and E), 400×). This image represents the solid area in the tumor|
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|Figure 4: Cystic spaces in tumor lined by outer vacuolated cells and the lumen filled with keratinous material. Solid areas show squamous pearls mimicking malignancy, but without any significant atypia (H and E, 100×)|
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| Discussion|| |
A PPT usually arises in the setting of single or multiple pilar cysts. A rapid increase in size signals the neoplastic transformation of the cyst into a PPT. The underlying stimulus for this transformation is not known, but thought to be due to trauma, irritation, or chronic inflammation. Lesions are usually single and firm to soft painless nodules. The most common location is the scalp (90%). Other reported sites include back, chest, groin, gluteal region,  thigh, vulva,  and eyelid.  Inflammation, ulceration, bleeding, and/or yellowish discharge may occur. The lesion may grow into a large, elevated, lobulated mass that may undergo ulceration; and thus greatly resemble squamous cell carcinoma.  The neoplasm is well circumscribed, with islands of squamous epithelium undergoing trichilemmal keratinization which is histological hallmark of PPTs. Ye et al.,  proposed a tentative stratification of PPTs into benign (group 1), low grade malignancy (group 2), and high grade malignancy (group 3). Group 1 PPTs are circumscribed with "pushing" margins and have modest nuclear atypia with absence of mitoses, necrosis, and angioinvasion; group 2 PPTs are similar to group 1, but showed irregular, locally invasive margins with involvement of the deep dermis, and subcutis; group 3 PPTs manifested invasive growth patterns, marked nuclear atypia, atypical mitosis, and geographic necrosis with or without involvement of nerves or blood vessels. It has been found that local regrowth is common with group 2 PPTs, while group 3 PPTs have metastatic potential.  Determining the malignant potential of a PPT may be challenging. Malignant PPTs are more likely to stain positive with p53 and Ki-67 compared to benign PPTs and trichilemmal cysts. 
The common differential diagnoses of PPTs are epidermoid cyst, cylindroma, and squamous cell carcinoma.  Cytologically, PPTs have relatively less amount of keratin and nests of squamoid and basaloid cells with abrupt anucleate keratinization;  whereas epidermoid cysts show a cleaner background with high cellularity of many nucleate and anucleate squmaes.  The important differential diagnosis for ulcerated PPT is squamous cell carcinoma and it can be ruled out by the absence of extensive areas of severe atypia and absence of invasion into the surrounding tissue.  In contrast to ordinary trichilemmal cyst, PPTs in addition show changes resembling keratinization of the follicular infundibulum giving rise to horn pearls, vacuolated cells containing glycogen like the outer root sheath cells, and prominent glassy layer of collagen. 
The prognosis of PPTs is excellent with complete excision. Local recurrences are common in tumors which are incompletely excised. Cases showing malignant transformation and invasion into cerebral sinuses causing death have been reported.
Our case emphasizes the necessity for detailed clinical examination along with pathological correlation to arrive at the diagnosis of ulcerated PPT which mimicks squamous cell carcinoma.
| References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]