PIGMENTED POLYMORPHIC LARGE CELL MELANOCYTOMA
HAVING FEATURES THAT BEST FIT AN EPITHELIOID BLUE NEVUS
Very large, intensely  hyperpigmented cells that are relatively round (epithelioid) or polygonal are found in a variety of backgrounds including the epithelioid blue nevus of Carney1, a minority of combined nevi, equine/animal type melanomas of humans2 and, rarely, in other human malignant melanomas. Hypomelanotic variants of these cells may also be seen. There are hyperpigmented spindle cells, fusiform cells or dendritic cells that are occasionally larger than those found in classical melanocytomas of Spitz (spindle cell nevus of Spitz) or in melanocytomas of Reed (pigmented spindle cell nevus of Reed) that are found either alone or in combination with the large, hyperpigmented epithelioid cells in similar settings.

Carney and Ferreiro coined the term epithelioid blue nevus to indicate a pigmented lesion characterized by the presence of  hyperpigmented globular and polygonal cells (they termed these epithelioid), spindle cells, dendritic cells , and lightly pigmented or nonpigmented polygonal cells. The latter cells had prominent nucleoli within vesicular nuclei. Inasmuch as they found these lesions while studying patients and families with the Carney complex (myxomas, spotty skin pigmentation, endocrine overactivity, and schwannomas), it is not surprising that they indicated that such lesions, particularly if multiple, were an important marker for this complex. Subsequent reports indicate this type of lesion occurs in the general population, including children, in the absence of the Carney complex. Therefore, it would not be necessary to conduct a search for cardiac myxomas or other serious problems associated with the Carney complex if the patient has a solitary epithelioid blue nevus in the absence of a positive family history and/or multiple cutaneous pigmentary lesions.

Childhood melanocytic lesions that have any kind of a spindle cell component are too often relegated to the Spitz' nevus category in spite of the fact that the some of these have few, if any, of the features described by Spitz. This may be due to the lack of an acceptable alternative diagnosis. The case presented below certainly is not a classical Spitz' nevus.  The term epithelioid blue nevus will suffice for this case if the viewer's opinion is not tainted by the implication that this is necessarily a harbinger of the Carney complex or that this is the human equivalent of the equine/animal melanoma. A term such as pigmented polymorphic large cell melanocytoma would  reflect the size as well as the diversity of morphology of the cells without  unwarranted biologic implications.

References:
1) 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.

2) Zembowicz A, Equine/Animal Type Melanoma; http://www.drmihm.com/Cases/case.cfm?CaseID=20


 This case was sent in by Jim Murphey. It is from a 4 year old patient who neither has evidence of the Carney complex nor a family history of the Carney complex. This lesion appeared about 3 years ago.
 
Scanning power view. There is massive involvement of the papillary and reticular dermis by pigmented cells. Judge for yourself whether you think it is symmetrical or not. It does look like the superficial dermal component has expansile properties. The reticular dermis is more diffusely infiltrated.
A medium power view. Keratinocyte hypertrophy of the type that can be seen in benign melanocytomas as well as in evolving melanomas (SSM's particularly) is present. The papillary dermis is packed by large, hyperpigmented cells that have round or polygonal outlines. Some are dendritic.
High power view of the epidermis. There is pagetoid spread of hyperpigmented dendritic cells. When cut at an angle that does not demonstrate a dendrite, these falsely resemble the pagetoid melanocytes of superficial spreading melanoma.
High power view of the dermoepidermal junction and papillary dermis. The very large, hyperpigmented round, ovoid, and polygonal cells resemble macrophages (melanophages) but these have very large nucleoli within vesicular nuclei, unlike macrophages. Large dendrites are also seen.
A  high  power view from within the reticular dermis. Some of the cells in this picture are less melanized than their neighbors. Vesicular nuclei contain very prominent nucleoli. There is a dispersed pattern of infiltration.
A high power view from another area within the reticular dermis. Some of the polygonal, hyperpigmented cells are in an erector pili muscle. Bizarre, wispy dendritic processes and large cytoplasms are in the upper right side of the picture.

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