Nevi are designated as 'combined' if they contain elements of two or more types of nevi that otherwise occur in pure form. Examples include combinations of ordinary nevi, spindle cell nevi (Spitz), blue nevi, cellular blue nevi, plexiform spindle cell nevi^ref, and nevi that contain spindle and/or epithelioid cell populations of the type found in this case.

The combined nevi that contain the cell population/s seen in this case were designated as common variant (pigmented spindle cell) combined nevi by Pulitzer et al^ref. Nevi of this type were designated as 'clonal nevi' or 'melanocytic nevi with focal atypical epithelioid cell components' by Ball and Golitz^ref.  Seab et al^ref excluded combined nevi as well as blue nevi and Spitz' nevi  from their cases published as 'deep penetrating nevus', but the spindle and epithelioid cell population depicted in this case were illustrated in pure form as being characteristic of one type (see their fig. 7) of deep penetrating nevus.

It is important to recognize the spindle and/or epithelioid cell population that is seen in this case since this population can lead to an erroneous diagnosis of malignant melanoma, particularly minimal deviation melanoma. This population usually is not present to the degree that is seen in this case.  A cluster of  associated pigmented macrophages will sometimes catch the eye when there is only a small focus. This population can be located anywhere within an ordinary nevus. I have the impression that these are found more frequently in congenital nevi but do not have any statistics to back this up.This population is usually hyperpigmented and often results in an atypical clinical appearance. Pleomorphism is often present, particularly in lesions that contain large foci of these unusual cells.

These cells are large, and the epithelioid cells characteristically have poorly defined cytoplasmic borders when found in clusters. Therefore, they differ from ordinary type A nevus cells. Hyperpigmented epithelioid cells similar to these are rarely encountered in Spitz' nevi. The nuclei are more dense than those found in  epithelioid blue nevi^ref. The spindle cells can be found in clusters, cell balls, or in poorly formed fascicles.
 

	Composite scan power view. Ordinary nevus cells are above the black line. There was no evidence of the radial growth phase of a melanoma.
	Low power view from the junction of the ordinary nevus part of the nevus (above the line) and the spindle and epithelioid cell component.
	Medium power view showing clusters of spindle cells having poorly defined cytoplasmic outlines and 'dusty melanization'. There is a suggestion of a fascicular pattern in the lower right part of the picture. A few epithelioid (round) cells are also seen. These cells are separated by native reticular dermis collagen bundles and by a small amount of specialized stroma. Note the pleomorphism in this single field.
	High power view illustrating some of the features noted previously. Spindle cells are in the lower right corner. There is a cluster of hyperpigmented epithelioid cells having poorly defined cytoplasmic outlines, and there are isolated epithelioid cells having distinct cytoplasmic outlines.
	Low power view of the bulbous protrusion of spindle and epithelioid cells into the subcutis.This type of bulbous protrusion is sometimes seen in cellular blue nevi. Although deep penetration is present, combined nevi were not included in the original description of 'deep penetrating nevus'.
	High power view of above. Cytoplasmic outlines are poorly defined for the most part. There is very little intervening stroma. An area such as this resembles an expansile nodule of minimal deviation melanoma.

References:

1. Barnhill RL, Mihm MC Jr, Magro CM.
    Plexiform spindle cell naevus: a distinctive variant of plexiform melanocytic naevus.
    Histopathology. 1991 Mar;18(3):243-7.

2. Pulitzer DR, Martin PC, Cohen AP, Reed RJ.
    Histologic classification of the combined nevus. Analysis of the variable expression of melanocytic nevi.
    Am J Surg Pathol. 1991 Dec;15(12):1111-22.

3. Ball NJ, Golitz LE.
    Melanocytic nevi with focal atypical epithelioid cell components: a review of seventy-three cases.
    J Am Acad Dermatol. 1994 May;30(5 Pt 1):724-9.

4. Seab JA Jr, Graham JH, Helwig EB.
    Deep penetrating nevus.
    Am J Surg Pathol. 1989 Jan;13(1):39-44.

5. Carney JA, Ferreiro JA.
    The epithelioid blue nevus. A multicentric familial tumor with important associations, including cardiac myxoma and psammomatous
    melanotic schwannoma.
   Am J Surg Pathol. 1996 Mar;20(3):259-72.

6. Moreno C, Requena L, Kutzner H, de la Cruz A, Jaqueti G, Yus ES.
    Epithelioid blue nevus: a rare variant of blue nevus not always associated with the
    Carney complex.
    J Cutan Pathol. 2000 May;27(5):218-23.

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