A 52-year-old man was examined for an ulcerated, rapidly growing reddish nodule. It was 5.5 cm high with an 11 x 6-cm base and located on the left clavicle. The lesion had been present for approximately 7 years, and the patient complained occasional burning and pain. Clinical differential diagnoses included cutaneous lymphoma, sarcoma, squamous cell carcinoma, and cutaneous metastasis. Histopathologic examination revealed a well-circumscribed tumor involving the whole dermis and the subcutis and composed of partially confluent aggregates of matrical cells admixed with eosinophilic cornified material containing shadow cells. In addition, multinucleated giant cells, areas of calcification and metaplastic ossification, edema, and hemorrhage were also observed. On the basis of histopathologic features, the diagnosis of pilomatricoma was made. Our report highlights an unusual clinical appearance of pilomatricoma that made us consider a variety of primary or secondary cutaneous neoplasms in its differential diagnosis.

Pilomatricomas in children: imaging characteristics with pathologic correlation.Pediatr Radiol. 2007 Jun;37(6):549-55. Epub 2007 Apr 17.

BACKGROUND: Although pilomatricoma commonly occurs in children, there is still a poor understanding of the imaging characteristics of pilomatricoma and lack of agreement regarding its imaging findings and histopathologic features. OBJECTIVES: To characterize the radiologic appearance of pilomatricomas on US, CT, and MR and to correlate the imaging findings with histopathologic features. MATERIALS AND METHODS: The imaging findings of 47 pilomatricomas on US (n = 17), CT (n = 31), and MR (n = 5) were retrospectively evaluated. Pathologic specimens of all cases were reviewed and compared with imaging findings. RESULTS: All lesions were well-circumscribed, subcutaneous nodules with partial attachment to the overlying skin. On US, the lesions were mostly hyperechoic with posterior acoustic shadowing and hypoechoic rim. On CT, they appeared as enhancing soft-tissue masses with varying amounts of calcification. MR findings were internal reticulations and patchy areas on T2-weighted images and contrast-enhanced T1-weighted images, corresponding to edematous stroma on pathology. Peritumoral inflammatory changes and connective capsule on pathology were well correlated with imaging findings. CONCLUSION: Pilomatricoma should be considered when US or CT shows a well-defined hyperechoic or calcific nodule in subcutaneous fat attached to the skin in children. MR images may be helpful in diagnosis. Pathologic findings are well correlated with imaging findings.