Pilomatricomas are uncommon benign hamartomas of the hair matrix, first described as calcifying epithelioma by Malherbe and Chenantais in 1880.[1] The peak incidence of occurrence of pilomatricoma is in the first and sixth decades and predominantly involve the head and neck area.[2] Several variants of pilomatricoma have been described, including bullous-like, perforating, giant, familial, anetodermic, and multiple. We report here a rare case of perforating pilomatricoma.

A 62-year-old female patient presented with a noduloulcerative lesion on her left preauricular area for 1-month. The lesion started as a pea-sized papule, which enlarged rapidly and developed ulcer at the center. The lesion was mildly painful, and there was a history of recurrent bleeding from the lesion. There was no other significant medical history. The general and systemic examination revealed no abnormality. On cutaneous examination, there was an ulcerated erythematous nodule of size 2 cm × 3 cm over left preauricular area. The central ulcerated area showed fleshy tissue with hemorrhagic crusting [Figure 1]. On palpation, the nodule was soft to firm in consistency and not fixed to the underlying structures. A skin biopsy was taken from the periphery of the nodule. The histopathology showed well-circumscribed tumor located in superficial dermis with ulceration of the overlying epidermis. There were islands of basaloid cells and eosinophilic keratinized shadow cells in upper dermis [Figure 2]. The blood investigations were within the normal limits. With these findings, a diagnosis of perforating pilomatricoma was made. The lesion was removed with elliptical excision.

Perforating pilomatricoma is a rare variant of pilomatricoma.[3] There are some differences in presentation of perforating pilomatricomas. Clinically, the lesions appear as inflammatory papules,[4] cutaneous horn like nodules,[5] craters, ulcers,[36] or keratoacanthoma.[7] In our case, the tumor was of 1-month duration, had grown rapidly and presented as an ulcerated nodule. Perforating pilomatricomas were reported to be situated in the upper portion of the dermis, contrary to the deeper location of the tumor islands in classic pilomatricoma.[345] The tumor islands in our case were also located in the upper dermis, and eliminated through the ulceration of central part of the skin. Uchiyama et al.,[5] suggested this phenomenon resulting from transepithelial elimination. However, some authors proposed that in patients with perforating pilomatricoma, the elimination of tumor components from ulcers with damage to the epithelial structures, should not be described as transepithelial elimination.[8]

The different unusual morphological presentations of pilomatricoma make its clinical diagnosis difficult. The correct preoperative diagnosis is demonstrated to be as low as 0.01% by Lan et al.[29] In our case, malignant neoplasm was also considered because of elderly age and rapid progression of the lesion. The histopathological study remains only truly reliable mean of diagnosis of pilomatricoma. The classical histology shows the presence of ghost or shadow cells and basophilic cells. However calcification and foreign body giant cell reaction is also common.[29] As the tumor matures, the basaloid cells degrade centrally forming the enucleated ghost, or shadow cells.

Pilomatricoma should be considered in the differential diagnosis of solitary noduloulcerative lesion as in the present case. However, one should be careful to rule out pilomatrical carcinoma at an elderly age.