lentigo maligna having a balloon cell component

LENTIGO MALIGNA HAVING A BALLOON CELL COMPONENT

Lentigo maligna (LM) is characterized by atypical lentiginous melanocytic hyperplasia in a background of sun-damaged skin. The viewer is referred to any of the standard texts for discussions of the pathology of this lesion. A few points deserve mentioning here:

Considerable variation in patterns of hyperplasia and in the cytology of the cells exists from case to case and, occasionally, within a given lesion. Therefore, sampling problems can lead to erroneous diagnoses, particularly on small biopsies. Slightly atypical lentiginous melanocytic hyperplasia, which I define as an atypical deviation from the pathology of solar lentigo insufficient to diagnose as lentigo maligna, should prompt the pathologist to request a larger sample. I arbitrarily require the atypical cells to be 'stacked up' as least three cell layers thick before making the diagnosis of LM. This 'stacking up' often results in the formation of clusters of cells resembling those of a banal junctional nevus. Therefore, a lesion that would otherwise be classified as a junctional nevus or dysplastic nevus should be looked upon with suspicion if there is evidence of significant solar damage. Involvement of pilosebaceous units, though not always present and not requisite for the diagnosis, should lead one to favor a diagnosis of lentigo maligna when confronted with a 'borderline' lesion.

Melanocytic balloon cells are, by definition, encountered in balloon cell nevi and in balloon cell melanomas. I do not recall having seen a balloon cell component in a lentigo maligna prior to this case.

This is a shave-type biopsy from a slowly enlarging, irregularly pigmented, asymmetrical, large macular lesion of the left cheek of an 82 year old female. These findings and history are typical for a lentigo maligna.

Composite low power view. An arrow points to a pilosebaceous unit (PS).

	High power view of the area in the red rectangle shown in the low power view. Severe solar elastosis and slightly atypical lentiginous melanocytic hyperplasia are present. The melanocytes are 'stacked up' about two cell layers thick.
	High power view of the area in the blue rectangle shown in the low power view. The melanocytes in the lower epidermis are 'stacked up' three or more cell layers thick and are forming junctional clusters. This finding, in the proper setting, is indicative of lentigo maligna.
	High power view of the area in the black rectangle shown in the low power view. Melanocytic balloon cells are illustrated.
	Medium power view showing pilosebaceous unit (PSU) involvement. Involvement of pilosebaceous units by atypical lentiginous melanocytic hyperplasia can be helpful in establishing the diagnosis of lentigo maligna in difficult cases.

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