Case Reports

Nevus Spilus: Is the Presence of Hair Associated With an Increased Risk for Melanoma?

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Nevus spilus (NS), also known as speckled lentiginous nevus, is characterized by background café au lait–like lentiginous melanocytic hyperplasia speckled with small, 1- to 3-mm, darker foci. Nevus spilus occurs in 1.3% to 2.3% of the adult population worldwide. Reports of melanoma arising within hypertrichotic NS suggest that hypertrichosis may be a marker for the development of melanoma. We present a case of a hypertrichotic NS without melanoma and also provide a review of previously reported cases of hypertrichosis in NS. We believe that NS has a lower risk for malignant degeneration than congenital melanocytic nevi (CMN) of the same size, and it is unlikely that hypertrichosis is a marker for melanoma in NS.

Practice Points

  • Nevus spilus (NS) appears as a café au lait macule studded with darker brown “moles.”
  • Although melanoma has been described in NS, it is rare.
  • There is no evidence that hairy NS are predisposed to melanoma.


 

References

The term nevus spilus (NS), also known as speckled lentiginous nevus, was first used in the 19th century to describe lesions with background café au lait–like lentiginous melanocytic hyperplasia speckled with small, 1- to 3-mm, darker foci. The dark spots reflect lentigines; junctional, compound, and intradermal nevus cell nests; and more rarely Spitz and blue nevi. Both macular and papular subtypes have been described.1 This birthmark is quite common, occurring in 1.3% to 2.3% of the adult population worldwide.2 Hypertrichosis has been described in NS.3-9 Two subsequent cases of malignant melanoma in hairy NS suggested that lesions may be particularly prone to malignant degeneration.4,8 We report an additional case of hairy NS that was not associated with melanoma and consider whether dermatologists should warn their patients about this association.

Case Report

A 26-year-old woman presented with a stable 7×8-cm, tan-brown, macular, pigmented birthmark studded with darker 1- to 2-mm, irregular, brown-black and blue, confettilike macules on the left proximal lateral thigh that had been present since birth (Figure 1). Dark terminal hairs were present, arising from both the darker and lighter pigmented areas but not the surrounding normal skin.

Figure 1. A 7×8-cm tan-brown macule studded with darker macules and slightly raised papules on the thigh that was later diagnosed as nevus spilus. Terminal hairs were present.

A 4-mm punch biopsy from one of the dark blue macules demonstrated uniform lentiginous melanocytic hyperplasia and nevus cell nests adjacent to the sweat glands extending into the mid dermis (Figure 2). No clinical evidence of malignant degeneration was present.

Figure 2. Histopathology revealed lentiginous melanocytic hyperplasia, most prominent at the tips of rete pegs, correlating clinically with the café au lait background coloration, and nevus cells adjacent to the sweat glands extending into the mid dermis, correlating with the blue-black papules (A and B)(H&E, original magnifications ×200 and ×100).

Comment

The risk for melanoma is increased in classic nonspeckled congenital nevi and the risk correlates with the size of the lesion and most probably the number of nevus cells in the lesion that increase the risk for a random mutation.8,10,11 It is likely that NS with or without hair presages a small increased risk for melanoma,6,9,12 which is not surprising because NS is a subtype of congenital melanocytic nevus (CMN), a condition that is present at birth and results from a proliferation of melanocytes.6 Nevus spilus, however, appears to have a notably lower risk for malignant degeneration than other classic CMN of the same size. The following support for this hypothesis is offered: First, CMN have nevus cells broadly filling the dermis that extend more deeply into the dermis than NS (Figure 2A).10 In our estimation, CMN have at least 100 times the number of nevus cells per square centimeter compared to NS. The potential for malignant degeneration of any one melanocyte is greater when more are present. Second, although some NS lesions evolve, classic CMN are universally more proliferative than NS.10,13 The involved skin in CMN thickens over time with increased numbers of melanocytes and marked overgrowth of adjacent tissue. Melanocytes in a proliferative phase may be more likely to undergo malignant degeneration.10

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