intraepidermal carcinoma

INTRAEPIDERMAL CARCINOMA, PROBABLY ECCRINE (a CEA was not done on this case)

Lesions having this type of pathology have also been described as malignant eccrine poroma, malignant hidroacanthoma simplex, and eccrine porocarcinoma, with the qualification that the lesion is not invasive. The term 'intraepithelial epithelioma of Jadassohn and Borst' is better avoided for a variety of reasons too lengthy to present at this time.

The presence of clusters of cytologically atypical epithelial cells that are morphologically distinct from their neighbors and separated from the dermoepidermal junction by several layers of normal keratinocytes is characteristic of this lesion. Occasionally, and not specifically, a peculiar form of parakeratosis that has been designated as 'necrosis en masse' in benign acrosyringeal tumors is seen over clusters of such cells that have reached the surface of the epidermis. The atypical cells are often positive for carcinoembryonic antigen (CEA). Verrucous architecture is sometimes present, but the architecture is variable from case to case. Invasive carcinoma that arises in this background has a propensity to metastasize (about 20%), so complete excision is advised.

The differential diagnosis includes other lesions characterized by the presence of clusters of cells within the epidermis that differ from their neighbors including:

LESION CLUSTER CHARACTERISTICS

Irritated seborrheic keratosis Squamous eddies composed of large keratinocytes that are not atypical

Clonal seborrheic keratosis Clusters of small keratinocytes that are not atypical

In situ squamous carcinomas (usually Bowenoid variants) If there is sparing of part of the epidermis by the atypical cells, the sparing is most often restricted to the basal layer (so-called 'eyeliner sign'). A CEA should be done in doubtful cases.

Junctional and compound nevi Junctional (intraepidermal) clusters do not spare the basal layer; not really a diagnostic problem

Malignant melanomas, particularly of superficial spreading type The basal layer is rarely spared by the atypical melanocytes. A CEA and an S-100 would solve the problem.

Mammary Paget's disease or extramammary Paget's disease The location of the lesion is helpful. Epithelial mucin is present in most of these cases, and this mucin is usually positive by the PAS method after diastase or is aldehyde fuchsin positive.

	Scan power view. There is no evidence of sun damage. This patient does not have seborrheic keratoses elsewhere.
	Low power view of above. There is sparing of multiple layers of keratinocytes by the atypical cell population, and such atypical cells are rarely seen at the dermoepidermal junction.
	High power view. Mitosis (m). If this image does not convey it, there is severe cytologic atypia.
	High power of the surface. Large parakeratotic remnants cap a surface collection of atypical cells (similar to necrosis en masse of benign acrosyringeal tumors).

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

LESION	CLUSTER CHARACTERISTICS
Irritated seborrheic keratosis	Squamous eddies composed of large keratinocytes that are not atypical
Clonal seborrheic keratosis	Clusters of small keratinocytes that are not atypical
In situ squamous carcinomas (usually Bowenoid variants)	If there is sparing of part of the epidermis by the atypical cells, the sparing is most often restricted to the basal layer (so-called 'eyeliner sign'). A CEA should be done in doubtful cases.
Junctional and compound nevi	Junctional (intraepidermal) clusters do not spare the basal layer; not really a diagnostic problem
Malignant melanomas, particularly of superficial spreading type	The basal layer is rarely spared by the atypical melanocytes. A CEA and an S-100 would solve the problem.
Mammary Paget's disease or extramammary Paget's disease	The location of the lesion is helpful. Epithelial mucin is present in most of these cases, and this mucin is usually positive by the PAS method after diastase or is aldehyde fuchsin positive.