Izabela Kranjčec

Jelena Roganović

Nives Jonjić

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308 ACTA DERMATOVENEROLOGICA CROATICAPilomatrixoma: A Benign Appendageal Tumor not Uncommon in ChildrenActa Dermatovenerol Croat   2015;23(4):308-309                          LETTER TO THE EDITORPilomatrixoma is a benign appendageal tumor, accounting for 1% of all benign skin lesions (1). It is mostly seen in children and young adults up to 20 years of age, the second peak being in the sixth and seventh decade of life. Pilomatrixoma usually mani-fests as a solitary, asymptomatic nodule on the head and less frequently on the upper and lower extremi-ties. The diagnosis is commonly based on biopsy and histological findings of basaloid cells with calcium deposits within a fibrin capsule. The therapy of choice is complete surgical excision with a wide peripheral edge, which has a low probability of recurrence. A 10-month-old male infant was referred to pe-diatric oncologist due to the formation located in the left temporal region, observed by his parents a month ago and associated with insect bite. The mass was painless, occasionally reddish-bluish, and had not changed in size. On examination a superficial, well circumscribed, and moderately firm lesion 1.5 cm in diameter was seen and palpated in the left tem-poral region (Figure 1). Plain radiography revealed no bone lesions. Ultrasonography demonstrated an ovoid, well-defined hypoechoic formation 1 cm in diameter, suggesting granuloma. Fine needle aspira-tion (FNA) was performed. Cytomorphologic analysis revealed the presence of abundant clusters of small cells with denting nuclei and basophilic cytoplasmic protrusions surrounded by extracellular pink fibrillary substance, some phagocytes, lymphocytes, granulo-cytes, scantily calcificated detritus, and scarce squa-mous cells, characteristic for pilomatrixoma. A com-plete surgical resection was done. Histopathological findings confirmed the diagnosis (Figure 2). Eight months after the excision there were no signs of local recurrence. Calcifying epithelioma was first described by Malherbe and co-workers in the 19th century (2). The tumor was later called pilomatrixoma to reflect the more accurate description of the origin from the hair follicle germinal matrix center. Pilomatrixoma is a be-nign solitary tumor usually occurring on the head. Multiple presentations have been described, some-times in more family members, mainly in association with myotonic dystrophy (3). Pilomatrixoma typically presents as a firm, hard mass, with reddish purple dis-coloration of the skin resulting from intrinsic hemor-rhage. It usually manifests as an asymptomatic nod-ule and rarely causes pain or itching due to ulceration and inflammation. The growth is rather slow, up to a Figure 2. Pilomatrixoma: (a) lower power view shows typical biphasic population; (b) with maturation the cells become larger with abundant eosinophilic cyto-plasm and nuclear piknosis; (c) foreign body reaction and (d) calcification is commonly present.Figure 1. A ten-month-old boy with an asyptomatic-solitary nodule in the left temporal region.  309ACTA DERMATOVENEROLOGICA CROATICAfew centimeters; rarely, giant pilomatrixomas have been reported. The majority of cases are diagnosed in the first two years of life. The sex distribution is still unclear, but slightly greater preponderance in males has been reported (4). Although genetic predisposition most likely plays a role in the pathophysiology of tumors, the etiology has yet to be understood. The mutations in the CNN-BT1 gene and beta-catenin/LEF disregulation have been identified as the major cause of tumorigenesis (5). In a few cases, a preceding insect bite or trauma have been reported. Although clinical presentation itself suggests pi-lomatrixoma, and ultrasonography is a helpful diag-nostic tool, misinterpretation of the lesion as an epi-dermal inclusion cyst, dermoid cyst, giant cell tumor, foreign body granuloma, and many others is frequent (6). FNA cytological features of shadow cells, primi-tive basaloid cells with a high nuclear/cytoplasmic ra-tio and foreign body giant cells are characteristic and allow a correct diagnosis (7). Nevertheless, misdiag-nosis is frequent. Definite diagnosis is established by biopsy and histopathological findings of ghost cells, calcium deposits, and foreign body giant cells (7). Spontaneous regression has not been observed. Complete surgical excision is the treatment of choice. Local recurrence seldom appears and is most likely due to incomplete resection. Malignant alteration has rarely been documented. It has been described in older men whose histopathological features included cellular pleomorphism, frequent mitotic figures and atypias (1).Our patient had a slow-growing asymptomatic head lesion. An insect bite was clearly noted in the medical history. FNA proved a reliable method for preoperative diagnosis of pilomatrixoma. We suggest that pilomatrixoma should be consid-ered in the differential diagnosis of solitary adnexal tumors in children. Although rare, local recurrence can occur and patients should be monitored. References:1.  Guinot-Moya R, Valmaseda-Castellon E, Berini-Ay-tes L, Gay-Escoda C. Pilomatrixoma. Review of 205 cases. Med Oral Patol Oral Cir Bucal 2011 Jul 1;16:e552-5.2.  Turhan-Haktanır N, Demir Y, Şahin Ö, Bükülmez A, Tüzüner M. Pilomatricoma: a review of six pediatric cases with nine lesions. Turk J Pediatr 2009;51:44-8.3.  Sherrod QJ, Chiu MW, Gutierrez M. Multiple pilo-matricomas: cutaneous marker for myotonic dys-trophy. Dermatol Online J 2008;14:22.4.  Abdel Mayem M, Mekhail P, Farag M, Shehata G, Al Sheikh M, Izzidien A, et al. Patient profile and outcome of pilomatrixoma in District General Hospital in United Kingdom. J Cutan Aesthet Surg 2013;6:107-10.5.  Xia J, Urabe K, Moroi J, Koga T, Duan H, Li Y, et al. Beta-Catenin mutation and its nuclear localiza-tion are confirmed to be frequent causes of WNT signaling pathway activation in pilomatricomas. J Dermatol Sci 2006;41:67-75.6.  Whittemore R K, Cohen M. Imaging and review of a large pre-auricular pilomatrixoma in a child. World J Radiol 2012;4:228-30.7.  Bansal C, Handa U, Mohan H. Fine needle aspira-tion cytology of pilomatrixoma. J Cytol 2011;28:1-6.Izabela Kranjčec¹, Jelena Roganović², Nives Jonjić³¹Pediatric Hematology and Oncology Department, Zagreb Children’s Hospital, Zagreb, Croatia ²Division of Hematology and Oncology, Depart-ment of Pediatrics, Rijeka University Hospital Centre, Rijeka, Croatia ³Department of Pathology and Patological Anat-omy, School of Medicine, University of Rijeka, Rijeka, CroatiaCorresponding author:Izabela Kranjčec, MD Pediatric Hematology and Oncology Department, Children’s Hospital Zagreb,Klaićeva 16, 10000 Zagreb,izabela.kranjcec@gmail.com,Received: January 19, 2015Accepted: October 20, 2015Letter to the editor Acta Dermatovenerol Croat2015;23(4):308-309

Pilomatrixoma: A Benign Appendageal Tumor not Uncommon in Children

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