Derm Dx: An uncommon neoplasm

Eccrine poroma is a rare benign adnexal neoplasm originating from the intraepidermal portion of the eccrine sweat gland duct, known as the acrosyringium.1 Poromas classically manifest as solitary, dome-shaped erythematous or flesh-colored nodules, papules, or plaques on the palms and...

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Eccrine poroma is a rare benign adnexal neoplasm originating from the intraepidermal portion of the eccrine sweat gland duct, known as the acrosyringium.¹ Poromas classically manifest as solitary, dome-shaped erythematous or flesh-colored nodules, papules, or plaques on the palms and soles and may be pruritic or painful.² Other areas of the body may be affected as well. These cutaneous lesions tend to occur in the middle-aged to elderly population, with no preference for race or sex.¹

These tumors are not commonly seen in everyday practice and their clinical presentation varies. As a result, eccrine poromas are often misdiagnosed as other more commonly seen cutaneous tumors.²

Several associations have been discovered between long-term radiation exposure and the development of eccrine poroma, specifically in those who have undergone electron beam therapy for mycosis fungoides.³ Associations have also been shown with hypohidrotic ectodermal dysplasia, chronic radiation dermatitis, and Bowen disease.²

 

Diagnosis of eccrine poroma is made through assessment of clinical and histologic findings. Dermoscopy can reveal commonly seen vascular patterns such as polymorphic, glomerular, linear-irregular, leaf and flower-like, and looped or hairpin variants. Of these, the leaf and flower-like pattern appears to be relatively limited to poroma.^1,2 Additional findings include the presence of vascular blush,¹ pink-white structureless areas, and interlacing white cords.² These cords give the appearance of a septated, lobular lesion and are fairly specific to eccrine poroma.

Histologically, these neoplasms are well-circumscribed nodules of small, uniform cuboidal or poroid tumor cells that commonly extend from the basal epidermis into the dermal layer and possess varying degrees of ductal differentiation.¹ Carcinoembryonic antigen immunostaining can be used to identify the presence of eccrine or apocrine ducts to aid identification.⁴ Cuboidal cells of eccrine poroma display characteristic compact eosinophilic cytoplasm that stains positive on periodic acid-Schiff test.⁵ Although eccrine poromas are benign, they may exhibit histologic characteristics that are also seen in malignant neoplasms, such as foci of necrosis, highly vascularized stroma, variable number of mitotic figures, or clear cell changes with small nuclei surrounded by a pale cytoplasm.⁶

Untreated lesions may potentially progress to eccrine porocarcinoma. These lesions can be distinguished from eccrine poroma by immunohistochemical staining for the overexpression of p16 and loss of retinoblastoma protein, which are more indicative of eccrine porocarcinoma.⁷

Curative treatment for eccrine poroma is by simple excision, shave, or electrosurgical destruction.⁴

Taylor Duke is a medical student at the University of Texas Medical Health Science Center at Houston, McGovern Medical School, and Maura Holcomb, MD, is a dermatology resident at Baylor College of Medicine in Houston, Texas.

References

1. Sawaya JL, Khachemoune A. Poroma: a review of eccrine, apocrine, and malignant forms. Int J Dermatol. 2014;53(9):1053-1061.
2. Shalom A, Schein O, Landi C, Marghoob A, Carlos B, Scope A. Dermoscopic findings in biopsy-proven poromas. Dermatolog Surg. 2012;38(7 Pt 7):1091-1096.
3. Kurokawa M, Amano M, Miyaguni H, et al. Eccrine poromas in a patient with mycosis fungoides treated with electron beam therapy. Br J Dermatol. 2001;145(5):830-833.
4. Bolognia JL, Jorizzo JL, Schaffer JV. Dermatology. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2012.
5. Dummer R, Pittelkow MR, Iwatsuki K, Green A, Elwan NM, eds. Skin Cancer—World-Wide Perspective. New York, NY: Springer; 2011.
6. Grant-Kels JM, ed. Color Atlas of Dermatopathology. New York, NY: Informa Healthcare USA, Inc.; 2007.
7. Gu LH, Ichiki Y, Kitajima Y. Aberrant expression of p16 and RB protein in eccrine porocarcinomas. J Cutan Pathol. 2002;29(8):473-479.