Extensive neurocristic hamartoma with bone marrow involvement.

Cutaneous neurocristic hamartoma (NCH) is a rare, pigmented lesion consisting of cells that aberrantly develop from the neurocrest. In addition to a dermal melanocytic component, NCH can also harbor neurosustentacular and neuromesenchymal components. NCH has many features in common with other dermal melanocytic neoplasm, such as blue nevi. Recognition of NCH is important not only because of the potential for misinterpretation as melanoma, but also because melanoma arise within these lesions over an unpredictable time frame and remain undetected because of the deep location and already pigmented background. We report a case of a 17-year-old man with a large NCH resected from the posterior scalp showing involvement of the bone marrow.