acral lentiginous melanoma #1

ACRAL LENTIGINOUS MELANOMA WITH 'MINIMAL DEVIANT' INVASIVE COMPONENT

This case illustrates some problems related to the diagnosis of melanomas arising in the setting of lentiginous radial growth, particularly in an acral location. A lentiginous component is not uncommon in benign acral nevi, and an occasional melanocyte is found in a pagetoid distribution in a minority of acral nevi, particularly in children. To make matters more treacherous, the early invasive component of an acral lentiginous melanoma may be deceptively benign appearing. The skin on palmar and plantar surfaces is not as readily molded by invasive melanoma, so a focus of invasion may not be readily palpable to the person doing the biopsy. Acral lentiginous melanomas are often large, and marked variation in diagnostic features can be found in different areas within such a lesion. If one is confronted with a small biopsy of a melanocytic lesion from an acral location and atypical features are noted, it is wise to recommend a repeat biopsy if the current biopsy does not include most of the clinical lesion.

As is true of melanocytic lesions elsewhere, if there is convincing evidence of 'in situ' melanoma in the epidermis, any melanocytic or nevoid cells within the dermis that are not clearly nevus cells should be interpreted as melanoma cells. When atypia of the dermal component is minimal, there will be a few false positive diagnoses, and examples of borderline minimal deviation melanoma and minimal deviation melanoma will be included. This is acceptable, particularly with regard to small biopsies, because there may be areas of unequivocal melanoma elsewhere in the clinical lesion.

Overview of this specimen. Click on the image to the left to go to a giant version of this (will take a long time to download, so you may not want to do this).

Composite high power view showing hyperchromatic spindle cells (HLC) in a lentiginous distribution involving the epidermis and an eccrine sweat duct.

Composite high power view showing hyperchromatic spindle cells (HLC) in a lentiginous distribution that span several rete ridges. The hyperchromatic spindle cells combined with this extensive distribution is sufficient to designate this as the intraepidermal component of an acral lentiginous melanoma. Dendritic cell hyperplasia is sometimes seen in this background. Sometimes the dendritic cells appear to be part of the neoplastic process in that they are cytologically atypical, but sometimes they lack atypical features and may be incidental. A dendritic cell (DC) is seen in an intraepidermal cluster of cells. Clusters of slightly atypical cells are found in the dermis. These are interpreted as melanoma cells of minimal deviant morphology.

Very high power view of the cells in the dermis.

Click on your browser's 'Back' button to go to the previous page.

	Composite high power view showing hyperchromatic spindle cells (HLC) in a lentiginous distribution involving the epidermis and an eccrine sweat duct.
	Composite high power view showing hyperchromatic spindle cells (HLC) in a lentiginous distribution that span several rete ridges. The hyperchromatic spindle cells combined with this extensive distribution is sufficient to designate this as the intraepidermal component of an acral lentiginous melanoma. Dendritic cell hyperplasia is sometimes seen in this background. Sometimes the dendritic cells appear to be part of the neoplastic process in that they are cytologically atypical, but sometimes they lack atypical features and may be incidental. A dendritic cell (DC) is seen in an intraepidermal cluster of cells. Clusters of slightly atypical cells are found in the dermis. These are interpreted as melanoma cells of minimal deviant morphology.
	Very high power view of the cells in the dermis.