Proliferating pilomatricoma

ARTICLE

Auteur(s) : Shiro Niiyama, Yasuyuki Amoh, Norimitsu Saito, Hiroshi Takasu, Kensei Katsuoka

Department of Dermatology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa, 228-8555 Japan

A 73-year-old man was evaluated for a solitary, stable nodule on the right lower leg. The nodule had been present for 6 months, and there was no history of trauma to the site. It was a lobulated, ulcerated, tumoral mass of 2-cm in diameter on erythema (figure 1A), and there was mild tenderness. The lesion was removed with a 5-mm margin. Microscopic examination revealed the surrounding basaloid cells were hyperchromatic, pleomorphic, and contained prominent nucleoli. Mitotic figures were present. Centrally, it was composed of keratotic material and shadow cells, and pale eosinophilic keratinocytes (figure 1B). The typical histologic pattern led to the diagnosis of proliferating pilomatricoma. Three years later, there was no evidence of either local recurrence or metastatic spread.

To date, 13 patients in 3 reports [1-3] of proliferating pilomatricoma have been described in the literature. There were 6 males and 7 females. Clinical examination mostly revealed solitary, painless, dome-shaped, nodules with a normal overlying epidermis and measuring 1.5 to 5.5 cm in diameter. Ulceration was present in 4 lesions (31%). Nine of the neoplasms were situated on the face (preauricular 2, retroauricular 2, cheek 2, eyebrow 1, temple 1, forehead 1), one on the upper arm, back, neck and lower leg. The main clinical differential diagnoses are squamous carcinoma, basal cell carcinoma, keratoacanthoma, epidermoid cyst, and metastasis.

Sassmannshausen and Chaffins [4] summarized 72 cases reported in the literature of benign and malignant pilomatricomas. Benign lesions occur more frequently in females (M:F = 2:3), whereas malignant lesions predominate in males (M:F = 3:1). Malignant pilomatricomas generally present as asymptomatic nodules and the mean tumor size is 4.2 cm (range 1 to 20 cm), which tend to ulcerate after attaining a size of 13 cm or more [5]. Clinically, benign and malignant pilomatricomas are similar only in their predilection for the head and neck area, upper extremity, and upper back. Concerning malignant pilomatricomas, local recurrence is common unless the tumor is excised with a wide surgical margin. Of the cases reported, 26 of 72 (36%) recurred locally and 8 (11%) had metastatic disease. Metastases to the lung, bone, and lymphatics have been described. In the literature there are 4 (6%) deaths attributed to metastatic pilomatricomas.

In comparison to stereotypical pilomatricoma, proliferating pilomatricoma reveals a higher number of mitotic figures implying that the increased number of basaloid cells within these lesions may be a function of the proliferation rate [1]. Malignant pilomatricoma mostly shows a relatively large, asymmetrical, poorly circumscribed lesion composed of several basaloid aggregations that vary markedly in size and shape, and often show jagged borders [6]. Within the dermis, the neoplasm exhibits extensive areas of neoplastic matrical cells with prominent atypia and numerous mitotic figures, and small foci of shadow cells. Malignant pilomatricoma may also show features suggestive of lymphatic or perineural invasion. In contrast, proliferating pilomatricoma reveals relative symmetry, smoothly outlined basaloid lobules, and there are no features suggestive of lymphatic or perineural involvement [1]. It is not presently known whether proliferating pilomatricoma is a precursor of malignant pilomatricoma. Regarding proliferating pilomatricomas, follow-up data available in 10 of the 13 patients (mean follow-up 20 months; range 6 months to 36 months) revealed local recurrences in one patient whose lesion recurred 3 times [1]. An excision with adequate margins is indicated. No lymph node metastases or distant metastases were recorded.

Acknowledgements

References

2 Hague JS, Maheshwari M, Ryatt KS, Abdullah A. Proliferating pilomatricoma mimicking pyogenic granuloma. J Eur Acad Dermatol 2007; 21: 688-9.

3 Sakai A, Maruyama Y, Hayashi A. Proliferating pilomatricoma: a subset of pilomatricoma. J Plast Reconstr Aesthet Srug 2007; 61: 811-4.

4 Sassmannshausen J, Chaffins M. Pilomatrix carcinoma: a report of a case arising from a previously excised pilomatrixoma and a review of the literature. J Am Acad Dermatol 2001; 44: 358-61.

5 Bremnes RM, Kvamme JM, Stalsberg H, Jacobsen EA. Pilomatrix carcinoma with multiple metastases: report of a case and review of the literature. Eur J Cancer 1999; 35: 433-7.

6 Manivel JC, Wick MR, Mukai K. Pilomatrix carcinoma: an immunohistochemical comparison with benign pilomatrixoma and other benign cutaneous lesions of pilar origin. J Cutan Pathol 1986; 13: 22-9.