balloon cell nevus

BALLOON CELL NEVUS

A few large, vacuolated nevus cells (balloon cells) are sometimes found in ordinary nevi. These may be mononuclear or multinucleated. When such cells constitute a significant part of the nevus (arbitrarily 50%), the nevus is designated a balloon cell nevus. The balloon cells in a balloon cell nevus may be indistinguishable from the balloon cells in a balloon cell melanoma. Therefore, the distinction between a balloon cell nevus and a balloon cell melanoma must be made on the basis of other criteria. Evidence of the radial growth phase of a melanoma, mitoses, and the presence of other types of melanoma cells in the vertical growth component would be characteristic of a balloon cell malignant melanoma. The absence of such findings plus the presence of other components of a benign nevus justify a diagnosis of balloon cell nevus. There are rare cases where the entire lesion is composed of balloon cells, and such cases may be insoluble.

The balloon cells are of such large size that it does not take many of them to form what appears to be an expansile nodule or plaque, thereby resembling the expansile nodule or plaque of an ordinary melanoma or a minimal deviation melanoma.

An isolated cluster of balloon cells is sometimes found in the background of a nevus, particularly a congenital nevus, in a manner analogous to the cells that form the distinctive part of lesions that have been designated as clonal nevi, deep penetrating nevi, and variants of combined nevi.

Scan power view of a shave biopsy of a nevus from an 11 year old patient.

Low power view of above. The balloon cells occupy a considerable part of the nevus, and they are associated with more superficial elements of an ordinary nevus. There is no evidence of the radial growth phase of a melanoma in this nevus.

High power view of above showing balloon cells intermingled with a few clusters of small nevus cells. These balloon cells cannot be distinguished from the balloon cells of a balloon cell melanoma.

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	Scan power view of a shave biopsy of a nevus from an 11 year old patient.
	Low power view of above. The balloon cells occupy a considerable part of the nevus, and they are associated with more superficial elements of an ordinary nevus. There is no evidence of the radial growth phase of a melanoma in this nevus.
	High power view of above showing balloon cells intermingled with a few clusters of small nevus cells. These balloon cells cannot be distinguished from the balloon cells of a balloon cell melanoma.