J Cutan Pathol 2010: 37: 1121–1122

John Wiley & Sons. Printed in Singapore

Copyright © 2010 John Wiley & Sons A/S

Journal ofCutaneous Pathology

Letter to the Editor

Pigmented classic poroma: a tumorwith a predilection for nonacral sites?To the Editor,

Classic poromas (CPs) are relatively commonbenign adnexal neoplasms that are typically locatedon the palms and soles, although other cutaneoussites can be affected. CPs are usually nonpigmented,but lesional pigmentation can occasionally be seen.

A 66-year-old man presented with a crustedpigmented nodule on his left forearm. The clinical

impression was concerning for nodular melanomaand an excisional biopsy was performed. Histopatho-logical review revealed broad anastomosing cordsand lobules of small monomorphous-appearingpolygonal epithelial cells extending from the epi-dermis into the subjacent dermis (Fig. 1A andB). Duct formation with focal cystic degenerationwas present centrally. Prominent melanin deposi-tion, confirmed by Fontana-Masson staining, was

Fig. 1. A) Broad anastomosing cords and lobules of small monomorphous polygonal epithelial cells extend from the epidermis into thesubjacent dermis, with microcystic change. B) Eccrine ductule formation with prominent melanin deposition within epithelial tumor cells(hematoxylin and eosin, ×4, ×40). C) Fontana-Masson stain confirming melanin pigmentation (×40). D) MART-1 immunohistochemicalstain confirming the presence of dendritic pigmented melanocytes throughout the lesion (×40).

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Letter to the Editor

identified within lesional cells (Fig. 1C). Intersperseddendritic pigmented melanocytes were noted bymelanoma-associated antigen recognized by T-cells(MART-1) and tyrosinase immunostaining (Fig. 1D).Atypical mitoses, cytologic atypia or other featuressuggestive of malignant transformation were notseen. Inflammatory cells and melanophages werepresent within the adjacent fibrovascular stromaand dermis. A diagnosis of pigmented CP wasrendered.

Poromas are benign adnexal tumors, with poroidor distal ductal differentiation, of eccrine or apocrinelineage. A number of variants have been described,including CP, hidroacanthoma simplex, dermalduct tumor and poroid hidradenoma.1 Combinedfeatures within a single lesion have been noted.1

Pigmentation of CP is uncommonly reported, asless than 20 citations exist in the literature.1– 6

Pigmented CPs appear to be more common innon-White populations and show a predilectionfor nonacral sites, in contrast to the moreprevalent nonpigmented variant.1,2 A pigmentedcongenital poroma has been described.3 Pigmentedporoid neoplasms with combined features of both(i) CP and poroid hidradenoma,1,7 (ii) CP andporocarcinoma,8 and (iii) hidroacanthoma simplexand porocarcinoma9,10 have also been reported. Ithas been hypothesized that melanocytic colonizationof a CP may be an indicator of malignanttransformation to porocarcinoma.3 However, thisfinding is at best speculative and has not beenvalidated by larger studies. The clinical appearanceof these lesions is due to the presence of pigmentedmelanocytes and melanin within the tumor, andmelanophages within adjacent stroma. Melanocyteswithin pigmented CP may be derived from either(i) the activation of persistent melanocytes within theeccrine acrosyringium, possibly reflecting regressionto a more primitive phenotype11 or (ii) the migrationand proliferation of epidermal melanocytes fromthe adjacent epidermis, under the influence ofupregulated tumor-derived melanocyte-stimulatingfactors (MSFs), such as endothelin-1.2 A symbioticrelationship between the epithelial cells and themelanocytes in these tumors has been suggested.6 Forintraepidermal lesions (i.e. hidroacanthoma simplex),it is possible that the melanin pigment may betransferred directly from adjacent normal basilarmelanocytes.9 It has been hypothesized that the

expression of endothelin-1 and other MSFs (i.e. stemcell factor and nerve growth factor) may be associatedwith the melanocytic colonization of CPs at nonacralsites.2 Despite the expression of MSFs in a significantminority of palmoplantar CPs, it is believed thatcertain characteristics of palmoplantar skin inhibitmelanocyte migration, proliferation and/or survival,thereby explaining the reported lack of pigmentationof CPs at acral sites.2

Amanda Phelps and Michael MurphyDivision of Dermatopathology, Department of

Dermatology, University of Connecticut HealthCenter, Farmington, CT, USA

e-mail: drmichaelmurphy@netscape.net

References1. Chiu HH, Lan CC, Wu CS, Chen GS, Tsai KB, Chen PH. A

single lesion showing features of pigmented eccrine poroma andporoid hidradenoma. J Cutan Pathol 2008; 35: 861.

2. Hu SC, Chen GS, Wu CS, Chai CY, Chen WT, Lan CC.Pigmented eccrine poromas: expression of melanocyte-stimulating cytokines by tumour cells does not always resultin melanocyte colonization. J Eur Acad Dermatol Venereol2008; 22: 303.

3. Wang SH, Tsai TF. Congenital polypoid pigmented eccrineporoma of a young woman. J Eur Acad Dermatol Venereol2008; 22: 366.

4. Aviles-Izquierdo JA, Velazquez-Tarjuelo D, Lecona-EchevarríaM, Lazaro-Ochaita P. Dermoscopic features of eccrine poroma.Actas Dermosifiliogr 2009; 100: 133.

5. Allende I, Gardeazabal J, Acebo E, Díaz-Perez JL. Pigmentedeccrine poroma. Actas Dermosifiliogr 2008; 99: 496.

6. Ohata U, Hara H, Suzuki H. Pigmented eccrine poromaoccurring on the scalp: derivation of melanocytes in the tumor.Am J Dermatopathol 2006; 28: 138.

7. Misago N, Kohda H. A single lesion demonstrating features ofeccrine poroma and poroid hidradenoma. J Dermatol 1995; 22:773.

8. Attili SK, Evans A, Fleming CJ. Recurrent pigmented eccrineporocarcinoma presenting as carcinoma erysipeloides. Clin ExpDermatol 2009; 34: e493.

9. Ueo T, Kashima K, Daa T, Kondoh Y, Yanagi T, YokoyamaS. Porocarcinoma arising in pigmented hidroacanthomasimplex. Am J Dermatopathol 2005; 27: 500.

10. Lee JY, Lin MH. Pigmented malignant hidroacanthomasimplex mimicking irritated seborrheic keratosis. J Cutan Pathol2006; 33: 705.

11. Robson A, Greene J, Ansari N, Kim B, Seed PT, McKee PH,Calonje E. Eccrine porocarcinoma (malignant eccrine poroma):a clinicopathologic study of 69 cases. Am J Surg Pathol 2001;25: 710.

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