Imaging mass spectrometry assists in the classification of diagnostically challenging atypical Spitzoid neoplasms.

BACKGROUND: Previously, using imaging mass spectrometry (IMS), we discovered proteomic differences between Spitz nevi and Spitzoid melanomas. OBJECTIVE: We sought to determine whether IMS can assist in the classification of diagnostically challenging atypical Spitzoid neoplasms (ASN), to compare and correlate the IMS and histopathological diagnoses with clinical behavior. METHODS: We conducted a retrospective collaborative study involving centers from 11 countries and 11 US institutions analyzing 102 ASNs by IMS. Patients were divided into clinical groups 1 to 4 representing best to worst clinical behavior. The association among IMS findings, histopathological diagnoses, and clinical groups was assessed. RESULTS: There was a strong association between a diagnosis of Spitzoid melanoma by IMS and lesions categorized as clinical groups 2, 3, and 4 (recurrence of disease, metastases, or death) compared with clinical group 1 (no recurrence or metastasis beyond a sentinel node) (P < .0001). Older age and greater tumor thickness were strongly associated with poorer outcome (P = .01). CONCLUSIONS: IMS diagnosis of ASN better predicted clinical outcome than histopathology. Diagnosis of Spitzoid melanoma by IMS was strongly associated with aggressive clinical behavior. IMS analysis using a proteomic signature may improve the diagnosis and prediction of outcome/risk stratification for patients with ASN.

Smooth muscle hamartoma associated with a congenital pattern melanocytic nevus, a case report and review of the literature.

Smooth muscle hamartoma (SMH) is a rare benign congenital or acquired lesion sometimes associated with Becker's nevus (Becker's melanosis). We report an unusual lesion with combined features of SMH and melanocytic nevus. The patient is a 49-year-old male with a history of a changing 'mole' on the left upper back. Clinical examination showed a solitary 1.2-cm nodule with central gray pigmentation. Histological examination showed a relatively well-circumscribed intradermal lesion. The superficial portion of the lesion consisted of melanocytes with nevoid morphology. The melanocytes had congenital pattern of distribution. Lesional melanocytes acquired a spindled morphology in the deeper dermis. The base of the lesion consisted of intersecting smooth muscle fascicles focally admixed with spindled melanocytes. The melanocytic component strongly expressed melanoma antigen recognized by T-cells-1 (MART-1) and HMB-45. The smooth muscle component was strongly positive for smooth muscle actin and h-caldesmon. Neither components showed significant cytological atypia or mitotic activity. Unlike a recently reported case of SMH combined with a melanocytic nevus and basal cell carcinoma, the current lesion did not occur in association with a Becker's nevus.