Journal of Plastic, Reconstructive & Aesthetic Surgery (2008) 61, 811e814

CASE REPORT

Proliferating pilomatricoma: a subset ofpilomatricoma

Atsuko Sakai a,*, Yu Maruyama b, Akiteru Hayashi a,c

a Department of Plastic and Reconstructive Surgery, Toho University Ohashi Hospital, Tokyo, Japanb Plastic and Reconstructive Surgery, Toho University Hospital, Tokyo, Japanc Plastic and Reconstructive Surgery, Toho University Sakura Hospital, Chiba, Japan

Received 26 June 2006; accepted 7 February 2007

KEYWORDSProliferatingpilomatricoma;Hair matrixdifferentiation

* Corresponding author. Address:Surgery, Toho University Ohashi HospitTokyo 153-8515, Japan. Tel.: þ81 03

E-mail address: prsnet@med.toho-

1748-6815/$-seefrontmatterª2008Britdoi:10.1016/j.bjps.2007.02.013

Summary Proliferating pilomatricoma is a histopathological entity that was proposed byKaddu et al. in 1997. Proliferating pilomatricoma represents a distinctive histopathologicalentity; it should be differentiated from other benign and malignant neoplasms with featuresof hair matrix differentiation. Kaddu reported that an incompletely excised proliferatingpilomatricoma may have a greater potential for local recurrence, because histopathologicallyit showed variable nuclear atypia and several mitotic figures. We report two patients withproliferating pilomatricoma and describe their clinical and pathological features.ª 2008 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Publishedby Elsevier Ltd. All rights reserved.

Proliferating pilomatricoma is a histopathological entitythat was proposed by Kaddu et al. in 1997.1 It can be re-garded as the conceptual framework for benign, proliferat-ing, or giant adnexal neoplasms that histopathologicallymimic their malignant counterparts.

However, to date, very few cases of proliferatingpilomatricoma have been described in the literature. Wereport two patients with proliferating pilomatricoma anddescribe their clinical and pathological features.

Plastic and Reconstructiveal, 2-17-6 Ohashi, Meguro-ku,3468 1251.u.ac.jp (A. Sakai).

ishAssociationofPlastic,Reconstruc

Case reports

Case 1

A 60-year-old female presented with a 2-month history ofa rapidly enlarging mass on her right forehead. The tumourcomprised a firm round mass measuring 35� 25� 30 mmwith ulceration (Fig. 1). Computed tomographic imagingrevealed a soft tissue shadow. Both T1- and T2-weightedmagnetic resonance imaging scans revealed isointensity(Fig. 2).

A second small tumour was observed on the righttemporal region. The forehead tumour was widely excisedwith a 3 cm margin, including the periosteum. The smalltemporal tumour was excised simultaneously.

tiveandAestheticSurgeons.PublishedbyElsevierLtd.All rightsreserved.

Figure 1

Figure 2

Figure 3

812 A. Sakai et al.

Histopathologically, the frontal lesion showed a largearea of basaloid cells with numerous mitotic figures.

However, in contrast to malignant tumours, the basaloidlobules revealed cystic spaces filled with fibrous material,histopathology showed a well circumscribed legion composedof smoothly outlined basaloid lobules (Fig. 3). The histopath-ological diagnosis of the forehead tumour was proliferatingpilomatricoma. On the other hand, the temporal tumour wasan ordinary pilomatricoma. The patient presented noevidence of local recurrence 3 years after the excision.

Case 2

A 49-year-old female presented with a painless, rapidlyenlarging mass on her posterior neck. The tumour wasobserved to be a dome-shaped, polypoid lesion, measuring34� 30� 25 mm, with small ulceration (Fig. 4). On both X-rayand computed tomogram, a tumor on her posterior neck pre-sented a soft tissue mass (Fig. 5). There were two other smallsubcutaneous tumours on her shoulder and the region justcaudal to the posterior neck tumour. Her past medical historyincluded several surgeries for removal of calcified tumoursfrom her back and neck during childhood. The tumourswere excised marginally and the wound was closed primarily.

Histopathological examination of the legion on the pos-terior neck revealed lobular proliferation of basaloid cells inassociation with adjacent focal areas containing eosino-philic, cornified material with shadow cells and a largernumber of mitotic figures. Scaning magnification showsa symmetrical, and the basaloid aggregations are incontinuity with cornified material incorporating shadow cells(Fig. 6). The histpathological diagnosis of this lesion was

Figure 4

Proliferating pilomatricoma 813

proliferating pilomatricoma, while the other two small tu-mours were pilomatricoma. The patient had no evidence oflocal recurrence 1 year after the excision.

Discussion

In 1997 proliferating pilomatricoma was first described byKaddu et al. as a histopathologically distinctive subset of

Figure 5

pilomatricoma.1 They examined retrospectively, and foundcases which showed unusual architectural features histo-pathologically. On clinical examination, a majority of thepatients were elderly individuals, the lesions werefound to be painless, dome-shaped, solitary, medium- tolarge-sized nodules in the head and neck regions. On histo-pathological examination, these were mainly found to becharacterised by a lobular proliferation of basaloid cellsin association with adjacent focal areas containing eosino-philic, cornified material along with shadow cells. Cytomor-phologically, the basaloid cells showed variable nuclearatypia and several mitotic figures, ranging from four to 15mitotic figures per high power field (HPF).1 There are, how-ever, no features suggestive of lymphatic or perineural in-volvement. Both of our patients were elderly individuals,and the lesions were located in their head and neck regions.On histopathological examination, the lesions revealedsolid and cystic lobules of basaloid cells in associationwith small or large foci of shadow cells and a large numberof mitotic figures indicating an increased number of basa-loid cells. These features are in agreement with thosedescribed by Kaddu. Hence, we diagnosed the lesions ob-served in both cases as proliferating pilomatricomas. Bothcases presented with pilomatricomas at the same time,with one patient having a further history of resection ofcalcified tumours. Although Kaddu did not refer to com-plication of pilomatricomas, complication of other calcifiedtumours might be one of the clinical features of proliferat-ing pilomatricoma. A large number of patients with prolif-erating pilomatricoma would need to be analysed todefine its clinical features.

Pilomatricoma, proliferating pilomatricoma, and pilo-matrical carcinoma show features of hair matrix differ-entiation.1e3 It is difficult to diagnose pilomatrical tumoursbased on the clinical features.4e7 Hence, the diagnosisneeds to be confirmed with histopathological and cyto-morphological examinations.1e3,8e10 Kaddu reported thatan incompletely excised proliferating pilomatricoma mayhave a greater potential for local recurrence compared toordinary pilomatricomas and presented an example of localrecurrence in one patient. It is not presently known

Figure 6

814 A. Sakai et al.

whether proliferating pilomatricoma is a precursor of pilo-matrical carcinoma. Therefore, all of these neoplasmasshould be excised with adequate surgical margins, andcareful follow-up examinations are strongly recommendedin all of these patients.

In conclusion, proliferating pilomatricoma representsa distinctive histopathological entity; it should be differ-entiated from other benign and malignant neoplasms withfeatures of hair matrix differentiation.

References

1. Kaddu S, Soyer HP, Wolf IH, et al. Proliferating pilomatricoma.J Cutan Pathol 1997;24:228e34.

2. Elder D. Lever’s Histopathology of Skin. 8th ed. Philadelphia:Lippincott Williams & Wilkins; 1997. p. 757e9.

3. Rosai J. Ackerman’s Surgical Pathology. 8th ed. St. Louis:Mosby; 1996. p. 138.

4. Aslan G, Erdogan B, Akoz T, et al. Multiple occurrence of pilo-matrixoma. Plast Reconstr Surg 1996;98:510e3.

5. Brandner MD, Bunkis J. Pilomatrixoma presenting as a parotidmass. Plast Reconstr Surg 1986;78:518e21.

6. Sasaki CT, Yue A, Enriques R. Giant calcifying epithelioma.Arch Otolaryngol 1976;102:753e5.

7. Kaddu S, Soyer HP, Cerroni L, et al. The clinical and histopath-ologic spectrum of pilomatricomas in adults. Int J Dermatol1994;33:705e8.

8. Marrogi AJ, Wick MR, Dehner LP. Pilomatrical neoplasms in chil-dren and young adults. Am J Dermatopathol 1992;14:87e94.

9. Hardisson D, Linares MD, Cuevas-Santos J, et al. Pilomatrixcarcinoma: a clinicopathologic study of six cases and reviewof the literature. Am J Dermatopathol 2001;23:394e401.

10. Mcculloch TA, Singh S, Cotton DW. Pilomatrix carcinoma andmultiple pilomatrixomas. Br J Dermatol 1996;134:368e71.