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Year : 2022  |  Volume : 9  |  Issue : 2  |  Page : 73-76

Pigmented epithelioid melanocytoma: A clinico-histopathological enigma

1 SVPIMSR Hospital, Smt. NHL Municipal Medical College, Ahmedabad, Gujarat, India
2 Shardaben Hospital, Smt. NHL Municipal Medical College, Ahmedabad, Gujarat, India

Date of Submission02-Jun-2022
Date of Decision16-Aug-2022
Date of Acceptance17-Aug-2022
Date of Web Publication27-Oct-2022

Correspondence Address:
Raju G Chaudhary
Department of Dermatology, SVPIMSR Hospital, Smt. NHL Municipal Medical College, Ahmedabad 380006, Gujarat
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijdpdd.ijdpdd_32_22

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Blue nevi are a group of congenital or acquired benign dermal melanocytic tumors. Various clinical and histological variants have been described.Epithelioid blue nevus (EBN), an uncommon variant may present as blue gray nodule over trunk, extremities which might occur either sporadically or in association with Carney complex. Due to clinical and histological overlap with other pigmented melanocytic lesions clinicopathological correlation is essential. We report a case of epithelioid blue nevus on dorsum of right foot in a 22-year-old man.

Keywords: Blue nevi, epithelioid blue nevus, pigmented epithelioid melanocytoma(PEM)

How to cite this article:
Shah PD, Chaudhary RG, Jagati A, Baxi KD. Pigmented epithelioid melanocytoma: A clinico-histopathological enigma. Indian J Dermatopathol Diagn Dermatol 2022;9:73-6

How to cite this URL:
Shah PD, Chaudhary RG, Jagati A, Baxi KD. Pigmented epithelioid melanocytoma: A clinico-histopathological enigma. Indian J Dermatopathol Diagn Dermatol [serial online] 2022 [cited 2023 Mar 20];9:73-6. Available from: https://www.ijdpdd.com/text.asp?2022/9/2/73/359769

  Introduction Top

Blue nevi are a group of congenital or acquired benign dermal melanocytic tumors which arise from residual melanin-producing cells that persist in the dermis of the scalp, sacral region, and dorsal aspect of the distal extremities.[1]

These persistent dermal melanocytes absorb longer wavelengths of light and reflect short wavelength blue light, thus making them appear blue in color - a phenomenon known as Tyndall effect.[2]

Blue nevi may present as blue to blue-black firm papule, macule, nodule or plaque often with variable age of onset.

On dermoscopy it appears as blue-grey, blue-black pigmented lesion, in a homogenous pattern, with structureless or amorphous areas (more common), or with dots and globules.[2]

Epithelioid blue nevus, a rare variant of blue nevus may occur either sporadically or with Carney complex.

  Case Report Top

We report the case of a 22-year-old man, with no significant past history, who presented with an asymptomatic, slowly progressive bluish skin lesion which was first noticed six years ago on the dorsum of the right foot. The lesion was initially pea-sized and gradually increased to present size. Growth was static for last two years. There was no history of bleeding, itching, pain or redness surrounding the lesion.

Clinical examination revealed a single, well-defined, soft to firm, symmetric 3 × 3 cm nodule with regular borders, homogenous blue - gray pigmentation with a few intervening darker bluish areas present over the dorsum of right foot [Figure 1].There was no local or regional lymphadenopathy.
Figure 1: Single bluish gray nodule over dorsum of right foot

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Dermoscopy (polarized light) showed bluish-gray structureless area with a few bluish black globules and darkly pigmented intervening areas. [Figure 2]
Figure 2: Dermoscopy- bluish gray structureless area with few bluish black globules and darkly pigmented intervening areas (contact, polarized mode with 10X magnification)

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Based on the clinical picture, blue nevus, nodular malignant melanoma, aneurysmal dermatofibroma, pigmented spitz nevus were considered as differential diagnoses and an excision biopsy was performed. The biopsy showed dense accumulation of dark brown melanin in the dermis, with spindled and epithelioid dermal melanocytes and intervening melanophages. Entrapment of reticular dermal collagen bundles was seen. There was no evidence of epidermal ulceration, lateral extension, pagetoid spread, marked cytological atypia or mitotic figures. The biopsy was suggestive of epithelioid blue nevus (benign type pigmented epithelioid melanocytoma) [Figure 3]a to d. Immunohistochemistry couldn’t be done due to refusal by patient.
Figure 3: a to d:- Dense accumulation of dark brown melanin in the dermis (H and E 10X,20X,40X,100X respectively, arrows in figure 3d depict -melanin)

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  Discussion Top

EBN (Epithelioid blue nevus) has been described in association with Carney complex, an autosomal dominant disorder characterized by endocrine abnormalities, myxomas, spotty skin pigmentation, Schwannomas.[3] However, as seen in our case they may also occur sporadically as solitary, blue-black, dome-shaped nodule or multiple nodules.[1],[4]

Pigment synthesizing melanoma(PSM)/Animal type melanoma(ATM), is a low grade variant of human melanoma which resembles that found in elderly gray horses. Due to overlapping clinical and histological features of EBN and ATM the term Pigmented Epithelioid Melanocytoma (PEM) was proposed to include them as benign and malignant ends of this histological spectrum, respectively.[5]

PEM can occur over a broad age range but is mainly seen in children, adolescents and young adults with no ethnic predominance. Most common sites of occurrence are extremities followed by trunk, head and neck. Less commonly, genitals and mucosal sites may be involved. Most PEM arise de novo but occasionally may be associated with dermal or congenital nevus.[5]

It has an indolent course with a tendency to spread to regional lymph nodes but distant metastasis is rare and has a good prognosis as compared to conventional malignant melanoma. Whether sentinel lymph node biopsy is needed for all cases of PEM is still controversial.[6]

Histologically, PEM is composed of heavily pigmented epithelioid and spindled melanocytes,as seen in our case. Two distinct population of epithelioid cells are seen:

  • (a) Abundant round to polygonal cells with heavily pigmented cytoplasm, round to oval vesicular nuclei, prominent nucleoli.

  • (b) Less numerous, less pigmented, large cell with abundant cytoplasm. In some cells, pigment accentuation is seen at the periphery of the cytoplasm without pigmentation around the nucleus, showing ‘egg-fried’ appearance.[4],[5]

Immunohistochemically PEM show positivity for MART-1, S-100 and HMB-45.[5]

No immunohistochemical markers are expressed exclusively in either melanocytic nevus or melanoma. Hence, these markers are used in a scaled manner rather than a positive/negative result. For example, HMB 45 shows a gradient pattern (positive- when only most superficial melanocytes stain, negative - equally involves superficial and deep cells) which is preserved in benign lesions and lost in malignant lesions. Ki-67 shows a similar pattern with an index value of <2% for melanocytoma and about 8% for melanoma. Mutations of protein kinase A regulatory subunit type 1 (PRKAR1) gene, protein kinase C alpha isoform (PRKCA) fusion ge nes have also been reported in pigmented epithelioid melanocytoma.[7]

The differential diagnosis for PEM include – blue nevus, malignant blue nevus, tumoral melanosis, Spitz nevus, deep penetrating nevus.

Blue nevi lack the characteristic pigmented and clear epithelioid cells of PEM.[5]

Malignant blue nevi (defined as malignant melanoma arising within a pre-existing blue nevus or melanoma arising at the site of prior biopsy or excision of a blue nevus) show infiltrative growth, necrosis, brisk mitosis, nuclear pleomorphism, and hyperchromasia..[5],[8]

Tumoral melanosis, a regressed stage of a melanocytic lesion, such as malignant melanoma consists of pigment-laden macrophages that are positive for CD 68. [5] Pigmented epithelioid Spitz nevus shows junctional melanocytic proliferation with heavily pigmented spindle cells arranged in fascicles. Deep penetrating nevus shows extension of melanocytes along adnexal structures, blood vessels and nerve bundles, which is absent in PEM.[6]

As there is no clinical or histological evidence of malignancy, the present case may be considered towards benign pole of pigmented epithelioid melanocytoma.

  Conclusion Top

PEM is a low-grade melanoma or borderline melanocytic tumor with an indolent course and metastatic potential, encompassing EBN and PSM. Because of its rarity and histological overlap with other pigmented melanocytic lesions, it becomes a diagnostically challenging entity which needs clinicopathological correlation.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Balin SJ, Barnhill RL Benign Melanocytic Neoplasms. In: Bolognia JL, Schaffer JV, Cerroni L, editors. Dermatology. 4th ed. Philadelphia: Elsevier; 2018. pp. 1954-88.  Back to cited text no. 1
Oliveira AHK, Shiraishi AFMC, Kadunc BV, Sotero PC, Stelini RF, Mendes C Blue nevus with satellitosis: Case report and literature review. An Bras Dermatol 2017;92:30-3.  Back to cited text no. 2
Bogart MM, Bivens MM, Patterson JW, Russell MA Blue nevi: A case report and review of the literature. Cutis 2007;80:42-4.  Back to cited text no. 3
Jang MS, Kang DY, Park JB, Kim ST, Suh KS Epithelioid blue nevus not associated with carney complex in a Korean patient. Indian J Dermatol Venereol Leprol 2012;78:521.  Back to cited text no. 4
Zembowicz A, Carney JA, Mihm MC Pigmented epithelioid melanocytoma: A low-grade melanocytic tumor with metastatic potential indistinguishable from animal-type melanoma and epithelioid blue nevus. Am J Surg Pathol 2004;28:31-40.  Back to cited text no. 5
Cheng PS, Chuang SS, Kuo TT, Lai FJ Pigmented epithelioid melanocytoma: Report of a case and review of 173 cases in the literature. Dermatologica Sinica 2012;30:57-61.  Back to cited text no. 6
Ferrara G, Argenziano G The WHO 2018 classification of cutaneous melanocytic neoplasms: Suggestions from routine practice. Front Oncol 2021;11:675296.  Back to cited text no. 7
Sun KL, Chang JM Epithelioid blue nevus. International Journal of Dermatology and Venereology 2020;3:186-7.  Back to cited text no. 8


  [Figure 1], [Figure 2], [Figure 3]


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