Pilomatricoma masquerading as metastatic squamous cell carcinoma

Educational Objective: At the conclusion of this presentation, the participants should be able to recognize the spectrum of clinical presentations and pathologic features of pilomatricoma and appreciate the possibilities for misdiagnosis. Objectives: To present a case of head and neck pilomatricoma mistaken for metastatic squamous cell carcinoma and review the relevant literature. Study Design: Case report. Methods: We present the clinical course of a 58 year old female who presented to a tertiary care center with a newly identified posterior neck mass. We review the literature pertaining to the spectrum of clinical presentations and pathologic features of pilomatricoma and provide cytopathologic imaging. Results: Cytopathologic analysis of a fine needle aspirate performed at our institution was consistent with metastatic squamous cell carcinoma. Thorough head and neck and dermatologic examination and radiographic evaluation with CT, MRI and PET/CT failed to show evidence for primary malignancy. The mass was radiographically characterized as a subcutaneous 0.5 cm occipital mass consistent with a lymph node and displaying a maximum SUV of 2.6. Neck dissection was deferred and panendoscopy and excisional biopsy of the neck mass was performed. Final histopathology revealed pilomatricoma. Conclusions: Pilomatricoma is a benign tumor commonly found within the pediatric population. It is typically diagnosed clinically but cytopathologic variability can result in confusion with more aggressive neoplasms. Appreciation of this variability may help prevent unintended and unnecessary invasive procedures as a result of erroneous diagnoses.