Atypical Junctional Melanocytic Hyperplasia

Atypical junctional melanocytic hyperplasia (AJMH) is a superficial process localized to the junctional region. This condition is distinctive from common acquired nevi. These changes are macular, often clinically ill-defined, may be large and uniformly darkly pigmented, with an asymmetric outline and irregular borders (29) (Table 4). The biologic behavior of AJMH is uncertain and unpredictable. However, AJMH may progress to melanoma and is associated with frequent local recurrence after incomplete removal, over months or decades. Immunosuppressed patients (e.g., transplantation patients) with AJMH may have a higher incidence of progression to melanoma (29). Figures 11-15 show the appearance of AJMH on the vulva (changes vary from mild to severe atypia).

Severely Dysplastic Nevi Excision
Figure 10 Genital compound nevus. Nests of cells are visible in the epidermis and dermis.

Diagnosis Symptoms

Clinical appearance

Differential diagnosis


Nevus Usually asymp-

Colors range from


No treatment


brown to pink

Atypical junctional

usually required

to dark blue


Excision for


changes in

Melanosis (lentigo)

appearance or



Grossly, it is not possible to distinguish the degree of atypia. It is interesting to note the combination of AJMH and lichen sclerosus in Figures 13 and 14. Further discussion on the association of lichen sclerosus and melanoma will follow.


As the name implies, AJMH has an increased number of predominantly single-unit, cytologically atypical melanocytes located in the basal layer of the epidermis and upper dermis, at the junction between the epidermis and the dermis (Fig. 16). AJMH may also arise in a nevus, where it often has extension of the atypical intrae-pidermal melanocytic hyperplasia beyond the shoulder of the nevus component; however, most AJMH lesions do not have a nevus component. In AJMH, the density of the melanocytes does not achieve that seen in melanoma, and pagetoid scatter of cells in the epidermis is minimal to absent.

AJMH may arise de novo, in association with another lesion such as melanosis or genital nevi, as a field effect in the setting of vulvar melanoma where it is often multifocal or represents the trailing edge of melanoma in situ (MIS). Thus, the significance of AJMH rests on the clinical context in which it is seen (29).


Suspicious areas should be removed with an attempt for clear margins. When atypia is found at the peripheral margins, a repeat attempt to obtain clear margins should be considered because these cells may progress to melanoma. Future studies investigating the molecular characteristics of AJMH are necessary to determine its significance. Until these markers are developed, complete removal is the only

Year Old Libia
Figure 11 Atypical junctional melanocytic hyperplasia, slight atypia on left labium minus.
Clitoral Excision
Figure 12 Higher magnification of Figure 11. Atypical junctional melanocytic hyperplasia on left labium minus.

way to ensure local tumor-free margins in clinical situations concerning for progression to melanoma (30). However, there are times when complete removal is not recommended and close observation is preferred, primarily based on morbidity of the procedure required for complete removal. Figure 15 illustrates AJMH with mild atypia on the clitoris of a 21-year-old patient. For the clitoral disease, close following was recommended rather than excision, after tissue biopsy confirmed the diagnosis.

Black Vulva
Figure 13 Whitened, crinkled appearance of the vulva with an area of brown-black discoloration, found to be atypical junctional melanocytic hyperplasia, moderate-to-marked atypia in association with lichen sclerosus.
Labial Brown Discoloration

Figure 14 Higher power of atypical junctional melanocytic hyperplasia, moderate-to-marked atypia in association with lichen sclerosus.

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