Extensive neurocristic hamartoma with skeletal muscle involvement

Neurocristic hamartomas (NCH) are rare pigmented skin lesions based in the deep subcutaneous tissues that may be either congenital or acquired. The clinical importance of these lesions is the potential for misdiagnosis and the development of malignant melanomas over a poorly described time course. Histological pleomorphism precludes meaningful random biopsies as a means of cancer surveillance. We present the case of an extensive NCH in a 67-year-old man, with a reported duration of greater than 50 years and no current clinical or histological indication of malignancy. Incisional biopsies of nodular areas showed bland-appearing pigmented cells that extended into subcutaneous adipose tissue and skeletal muscle. The specimens contained numerous clusters of differing configurations and cell types. Positron emission tomography (PET) scanning was used as an adjunct to physical examination in follow up. A PET-avid mass was detected but proved to be a banal nodular melanocytic proliferation within the NCH. In conclusion, NCH may be characterized by extensive deep tissue involvement in the absence of overt malignancy. The possible development of malignant melanoma in such lesions warrants close surveillance.