Balloon Cell Nevi and Balloon Cell Melanomas: What Are They?

Abstract

Balloon cell nevus was first described by Judalaewitsch [1] over a century ago in 1901. The first detailed case report was in 1935, when Miescher described a balloon cell nevus in a nine-year-old boy [2]. Miescher in this article erroneously hypothesized that a transformation of nevus cells into sebaceous cells produced a balloon cell. It is now known that a balloon cell is a nevocellular naevus [3]. The most common anatomical sites are the head and neck, followed by the trunk and extremities [4]. The significance of the balloon cell formation appears to be due to the degeneration of melanosomes and the progressive vacuolization that results [5]. Many balloon cell nevi resemble benign intradermal nevi or other benign lesions and are possibly under-diagnosed as a result. It is important to understand this pathophysiology especially as balloon cell malignant melanoma is known to occur and makes up 0.15 % of all cutaneous melanomas [6]. The article presented here is of two cases that were clinically not diagnosed – the first thought to be an intradermal nevus but turned out to be balloon cell nevus; the second, which resembled a seborrheic keratosis, was a malignant melanoma on biopsy. As in many instances, clinically benign intradermal nevi may not be biopsied, this entity may well be under-diagnosed. Further, as junctional activity has been known to occur over an incompletely removed balloon cell nevus, it may represent a precursor form of a dermal nevus cell [7]. Another notable feature of this balloon cell melanoma case however, is that it is pigmented (unlike reported balloon cell melanomas) and unequivocal balloon cells are seen in the dermo-epidermal junction. This has never been previously reported and is inconsistent with the previous hypothesis that a balloon cell melanoma is a vertical growth phase melanoma of dermal origin.