Rapid frozen section immunostaining of melanocytes by microphthalmia-associated transcription factor.

Mohs micrographic surgery (MMS) has increasingly become an accepted therapy for melanoma in situ on chronically sun damaged skin (CSDS). However, melanocytes are difficult to locate in frozen material on hematoxylin and eosin. In addition, determining the cut-off between the melanoma and the "atypical melanocytic hyperplasia" in CSDS can be challenging in frozen or formalin-fixed paraffin-embedded sections, with or without immunohistochemistry (IHC). In this article, we report the use of a rapid, 35-minute protocol using microphthalmia-associated transcription factor (MITF) IHC for identifying melanocytes in frozen tissue for its potential use in MMS. In contrast to melanoma antigen recognized by T cells (MART-1), MITF is a nuclear stain, which simplifies identification of melanocytes and quantification of melanocytic parameters. In this study, MITF IHC in frozen sections yielded equivalent melanocyte nuclear diameter and density measurements compared with formalin-fixed paraffin-embedded sections. Nuclear diameter measurements obtained with MITF were similar to that previously reported with MART-1, but the melanocyte density figures were lower. Reliable labeling of melanocytes in frozen sections required the use of diaminobenzidine (DAB) chromogen with Giemsa counterstaining and a buffer devoid of surfactant. Our experience with MITF IHC indicates that it is a dependable immunostain in frozen sections, and may prove to be useful in MMS as an adjunct to hematoxylin and eosin and MART-1 IHC for interpretation of margins for melanoma in situ on CSDS.

Surgical management of melanoma-in-situ using a staged marginal and central excision technique.

Melanoma-in-situ (MIS) represents 45% of all melanomas. The margins of MIS are often poorly defined with extensive subclinical disease. Standard fusiform excision with 5-mm margins results in positive margins in up to a third of cases. To decrease the incidence of involved margins, we use a staged excision approach for MIS. First, patients undergo excision under local anesthesia of a 2- to 3-mm "contoured" rim of tissue optimally 5 mm beyond the visible extent of the lesion. Formalin-fixed paraffin-embedded en face sections from this excision are then evaluated, if necessary with the aid of immunohistochemical stains. Any positive margins are further excised. When all margins are negative, the central area is then excised and reconstructed. A total of 61 patients with MIS or lentigo maligna melanoma underwent staged contoured excisions from 2004 to 2007 at Moffitt Cancer Center. We analyzed data only from patients with MIS of the head and neck. Patients with known invasive melanoma or non-head and neck primary disease were excluded. Demographics, tumor characteristics, margin status, number of stages, and type of reconstruction and recurrences were evaluated. Forty-nine patients with MIS of the head and neck, 28 (57%) male and 21 (43%) female, 42 to 88-years-old (median 72; mean 70), underwent staged contoured margin excision before definitive central tumor excision and reconstruction. The final surgical defect size ranged from 2 to 130 cm(2) (median 16 cm(2)). Twelve patients (24%) required reexcision of at least one margin; the median number of reexcisions was 1 (range 1-2). There seemed to be a positive association between lesion size and margin status (as well as number of excisions needed to clear the margin). Unsuspected invasive melanoma was found in the central specimen in six patients (12%). Even small tumors could have unsuspected invasive melanoma: invasive cancer was seen in 4 (21%) of 19 tumors < or =2 cm in greatest dimension and 2 (7%) of 30 > 2 cm, respectively. Surgical defects were reconstructed with flaps in 18 (37%), full-thickness grafts in 20 (41%), and split-thickness grafts in 10 patients (20%). Median time from first margin excision to completion/final reconstruction was 7 days (range 7-63 days). No local recurrences have been reported at a median follow-up of 14 months (range 1-36 months). This technique allows for careful margin analysis and subsequent central tumor excision with simultaneous reconstruction. This approach minimizes the need for a second major operation, which would have been necessary in 24% of our patients if treated by a one-stage excisional approach. It is noteworthy that 12% of MIS patients had invasive melanoma in the final excision specimen. This reinforces the importance of adequate full-thickness biopsies of suspicious pigmented lesions before any type of surgical management. With short follow-up, local control has been achieved by this technique in 100% of cases.

Surgical management of melanoma in situ on chronically sun-damaged skin.

BACKGROUND: Lentigo maligna (LM) commonly presents as a slow-growing pigmented macular lesion in chronically sun-damaged skin and may progress to invasive melanoma. Many regard it as a subtype of melanoma in situ (MIS), and surgical excision remains the preferred treatment, but standard 5-mm surgical margins recommended for typical MIS are often insufficient for LM due to its indistinct borders both clinically and histologically. METHODS: A search of the literature was conducted to review specialized surgical techniques for the treatment of LM, focusing on methods that employ total peripheral margin assessment prior to definitive closure, using either frozen or permanent histologic sections. RESULTS: Many investigators have reported surgical modalities utilizing permanent sections for margin control, including variations of the "square" procedure and "perimeter" technique. Recurrence rates are low with these methods, but only short-term data have been reported. Similarly, several studies have demonstrated the efficacy of Mohs micrographic surgery (MMS) for treatment of MIS, with recurrence rates generally less than 1% over 3 to 5 years of follow-up. Many investigators have had success with immunohistochemical stains to identify melanocytes on frozen sections, aiding margin assessment in MMS. CONCLUSIONS: Compared to standard excision, methods that employ surgical margin control offer superior cure rates for LM and should be utilized when available. Total peripheral margin assessment using staged excisions and permanent sections is a simple and effective alternative to MMS for institutions that lack the resources for intraoperative frozen section analysis.