Giant pilomatricoma with atypical features: report of a case of aggressive pilomatricoma in an adult

Abstract Introduction/Objective Pilomatricoma, also known as pilomatrixoma or calcifying epithelioma of Malherbe, is a relatively common, benign tumor of the hair matrix. It typically presents as a small (~1cm), dermal based mass in the head and neck region of children and young adults (under 20 years) with predominance for males, but can occur in any age. In contrast, malignant pilomatricoma is typically larger (1 to 10 cm) and occurs later in life (50-60 years). Aggressive pilomatricoma is a variant of pilomatricoma that tends to occur in children and demonstrates atypical features such as increased matrical cells and nuclear atypia, but insufficient for a classification as pilomatrical carcinoma. Here, we presented a case of a large (14.5 cm) aggressive/atypical pilomatricoma that occurred in an adult. Methods/Case Report A 45 year-old-female presented to the emergency department with a posterior neck mass which has been slowly enlarging for years. Recently, it became painful with sanguineous discharge which prompted her to seek medical attention. CT scan revealed a lobulated, pedunculated mass with fat and fluid components. An excision was performed. Gross examination revealed an ulcerated mass measured 14.5 cm in greatest dimension. Scattered calcifications were present. Microscopically, nests of basaloid cells with scattered shadow cells are present consistent with matrical differentiation. A multinodular growth pattern with central necrosis was evident. Nuclear atypia characterized by prominent nucleoli and nuclear overlapping was identified. Results (if a Case Study enter NA) NA Conclusion Histopathologic criteria to reliably differentiate between benign and malignant pilomatrical tumors are not well-established. Tumor ulceration, asymmetry, irregular borders, multinodular growth pattern, marked cytologic atypia, prominent necrosis, lymphovascular invasion, and perineural invasion may be used in favor of malignancy. Our case showed focal confluent necrosis, ulceration, multinodular growth pattern, and cellular atypia but lacked other features that indicative of unequivocal malignancy. The resection margins were negative for tumor. Clinical followup was negative for signs of recurrence or metastasis after two years. We presented this case to show the large size that aggressive pilomatricoma can reach and to emphasize the difficulty in differentiating benign from malignant pilomatrical tumors in borderline cases.