Melanoma In Situ

MIS is defined as Stage 0, confined to the epidermis and adnexal epithelium. It was classified as a subset of the International Society for the Study of Vulvovaginal Disease classification of'VIN (31) but has subsequently been discarded in the newer classification (31a). The concept of MIS was first described in 1949. In 1992, a panel at the Consensus Development Conference sponsored by the National Institutes of Health officially acknowledged this diagnostic category (32). The terminology was inspired by that of cutaneous squamous cell carcinoma; however, there is one major difference. Squamous cell carcinoma in situ is a premalignant condition, whereas MIS is considered a malignancy with a risk of metastasis, where there is an inability to detect an invasive component with tissue processing with standard histopathological techniques.

MIS often presents as a macular deeply pigmented lesion, initially uniform in appearance, but with time develops asymmetry, irregular borders, and color variegation (Table 5).

Histopathology

MIS is characterized histologically by a proliferation of malignant melanocytes confluently in the epidermis (Fig. 17). In the mucosal lentiginous type, the melanoma cells are arrayed predominantly in single cells in association with elongation of rete ridges. Pagetoid intraepidermal spread of melanoma cells is usually minimal to

Frenulum Clitoris
Figure 15 Atypical junctional melanocytic hyperplasia, slight atypia on prepuce, frenulum, and clitoris.
Melanoma Situ Labia
Figure 16 (See color insert) Atypical junctional melanocytic hyperplasia of the vulva. Melano-cytes with slight cytologic atypia are arrayed as solitary cells along the basal layer of the epidermis.

absent. In contrast, MIS of the superficial spreading type has prominent pagetoid scatter of melanoma cells in the epidermis.

Treatment

Excision with 0.5 to 1 cm margins is recommended for treatment. Positive margins require additional excision until clear histopathological margins are obtained. Additionally, referral to a melanoma specialist is indicated to examine the entire skin surface, which is at increased risk of additional primary melanomas, and complete melanoma education and prevention (33).

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