Poroma: a review of eccrine, apocrine, and malignant forms Jennifer L. Sawaya1, MSIII, and Amor Khachemoune2, MD, FADD, FACMS
1 University of Nevada School of Medicine, Las Vegas, NV, and 2Dermatology Service, Veterans Affairs Hospital, New York, NY, USA
Correspondence Amor Khachemoune, MD, FADD, Dermatology Service Veterans Affairs Hospital 800 Poly Place Brooklyn NY 11209 USA E-mail: [email protected]
Abstract Poroma is a benign adnexal neoplasm of the terminal sweat gland duct. Although poromas have traditionally been thought to originate from the eccrine sweat gland, there have been cases of apocrine etiology as well. Eccrine and apocrine poromas typically present as erythematous or flesh-colored nodules on the palms and soles. As these features overlap
with a multitude of differential diagnoses, it is imperative to have a firm understanding of the characteristics that make the diagnosis of poroma. In addition, the malignant counterpart to the poroma, the eccrine porocarcinoma, manifests in a similar nonspecific fashion. Case studies and literature reviews have contributed immensely to our present knowledge of poroma and porocarcinoma. Given the rarity of these neoplasms, however, there remains a relative paucity of information on atypical presentations and rates of malignant transformation. In this article, the epidemiology, clinical presentation, diagnosis,
Funding sources: The authors have no funding sources to declare.
and management of poroma and porocarcinoma will be reviewed. This systematic
Conflicts of interest: None.
approach may serve as a guide in navigating the diagnostic dilemma of these rare
A poroma is a benign adnexal neoplasm originating from the intraepidermal portion of the sweat gland duct, known as the acrosyringium. It is often grouped within the greater classification of acrospiroma that also includes dermal duct tumors, hidroacanthoma simplex, and nodular, clear cell, and poroid hidradenomas. Poroma was first described by Pinkus et al.1 in 1956 and was initially classified as a tumor originating from the eccrine sweat gland. Over time, this classic description has been challenged, and more recent data suggest that apocrine components may be present as well.2 In 1963, Pinkus and Mehregan wrote an original report detailing the first case of eccrine porocarcinoma arising from the intraepidermal ductal portion of the eccrine sweat gland.3 These malignant tumors may arise de novo or may develop from a pre-existing poroma through degenerative progression. The percentage of porocarcinomas transformed from benign eccrine poroma has been reported to be as high as 100% in a study by Shaw et al.4 sampling 27 cases. When looking at the actual transformation rates of the benign counterparts, however, it has been found that only 18% of poromas went on to become porocarcinoma.5 While the exact etiology remains unclear, the progression to malignancy appears to take a mean of 8.5 years.6 In this review, we will be highlighting the known facts about eccrine and apocrine poromas as well as eccrine porocarcinoma. We will begin with a discussion of clinical ª 2014 The International Society of Dermatology
presentation, epidemiology, and risk factors for each of the conditions. We will then progress on to histologic, dermatoscopic, and immunohistochemical findings. The differential diagnoses for both tumors will be listed, and consideration will be given to their individual features. Finally, we will conclude with a review of management strategies. Clinical presentation Clinically, a poroma typically presents as solitary domeshaped papule, plaque, or nodule. It is commonly described as skin-colored, pink, red, white, or even blue.7 Its surface can range from smooth to verrucous, and it has been described as ulcerative in some cases.8 While a poroma is generally found on an acral location, it can be located on almost any cutaneous surface. Its most common location is on the palmar or plantar surface (Fig. 1).9 It is important to note that poroma has been documented on the trunk, face (Fig. 2), and neck as well.10 It is generally slow growing and asymptomatic for the patient, although some patients may experience pain and itching.7 In rare cases, the patient may present with poromatosis and have multiple acral or widespread poromas at the time of diagnosis.11 Eccrine porocarcinoma presents as a firm, commonly asymptomatic nodule that is erythematous to violaceous in color and usually males in the 6th to 8th decade Erythematous hyperkeratotic or ulcerative plaque, nodule, or tumor on the sun-exposed areas of elderly men and women
Anaplastic, glycogen-rich cells with eccrine ductal structures, nuclear atypia, and necrosis. May be adjacent to a benign poroma Hyperkeratosis, epidermal hyperplasia and islands of squamous cells with central keratinization (keratin pearls). May see a dermal mixed inflammatory infiltrate Clonal keratinocytic proliferation with or without full thickness atypia With cytoplasmic bridges but no mucin or GCDFP-15 Epidermis infiltrated by neoplastic cells with pale, expanded neoplasm. No intercellular bridges, positive for mucin and GCDFP-15 Epithelioid, spindled, or desmoplastic morphology. Nuclear atypia, solar elastosis, poorly differentiated cells without melanin
Brown et al.12
Squamous cell carcinoma (SCC) Bowen’s disease (Squamous cell carcinoma in situ) Paget’s disease Amelanotic melanoma
Well-circumscribed erythematous plaque on a non sunexposed area Macular erythema with a sharply defined border and possible erosion or crusting commonly associated with breast carcinoma or internal malignancy Erythematous macule or patch on sun exposed areas, plaque or nodule without epidermal change, or exophytic nodule commonly on head, neck, upper and lower extremities.
simple excision. If the lesion recurs after excision or presents with ulceration, bleeding, pain, or accelerated growth, one should maintain a suspicion of eccrine porocarcinoma and investigate the lesion accordingly. Although some porocarcinomas arise de novo, there are a sufficient number of tumors, up to 100% in some studies, which originate from poromas. Immunohistochemistry on excised specimens has been suggested as a method in which to identify the transformation to malignancy on a molecular level. Although there are numerous treatment options for eccrine porocarcinoma, interference at an early stage could prevent the high rates of local recurrence and metastasis. At this time, there is a paucity of information regarding the recurrence and malignant transformation rate of poroma. In the future, it will be interesting to see how an expansion of our current knowledge of poroma and porocarcinoma may alter the management and outcomes of these rare tumors. Review questions (answers are available after references) 1 Which of the following statements are true? a. A poroma is a benign adnexal neoplasm of the intradermal portion of the sweat gland b. Poromas are most likely to occur in the second decade of life c. The most common location of a poroma is the back d. Patients with poromas are typically asymptomatic at the time of presentation e. Poromas typically transform into porocarcinomas within a 2-year period 2 Which of the following have not been implicated in the development of porocarcinoma? ª 2014 The International Society of Dermatology
Cheung et al.35 Gualandri et al.36
a. Chronic radiation exposure b. Prolonged use of chemotherapeutic agents c. Sarcoidosis d. Chronic lymphocytic leukemia e. Human immunodeficiency virus 3 A 60-year-old woman presents with a solitary, erythematous dome-shaped nodule on the left side of her face. The lesion has a small ulceration on its surface. She has noticed occasional itching and spontaneous bleeding. Which of the following characteristics is most suggestive of malignancy? a. Her age b. Occasional itching c. Erythematous color d. The location of the lesion e. Spontaneous bleeding 4 All of the following are histologic characteristics of eccrine poroma except: a. Extension of epidermal cells into the dermal layer b. PAS-negative cytoplasm c. Monomorphic cells with ovoid nuclei d. Highly vascularized stroma e. Foci of necrosis en masse 5 Which of the following patterns of immunohistochemical staining are representative of porocarcinomas? a. CEA negative, PAS positive, p16 immunoreactive, Rb nonreactive b. CEA positive, PAS positive, p16 immunoreactive, Rb nonreactive c. CEA positive, PAS positive, p16 immunoreactive, Rb immunoreactive d. CEA negative, PAS negative, p16 nonreactive, Rb non-reactive e. CEA positive, PAS negative, p16 immunoreactive, Rb immunoreactive International Journal of Dermatology 2014, 53, 1053–1061
6 Acrospiromas are further classified based on their location within the sweat gland. Which of the following pairs are not correctly matched? a. Intradermal: dermal duct tumor b. Intraepidermal: hidroacanthoma simplex c. Intradermal: hidradenoma d. Juxtaepidermal: eccrine poroma e. Juxtaepidermal: hidradenoma 7 Which of the following vascular patterns have not been observed in the dermatoscopic evaluation of eccrine poroma? a. Hairpin b. Flower and leaf c. Glomerular d. Mosaic e. Linear-irregular 8 A 12-year-old boy presents with a solitary, erythematous, dome-shaped nodule overlying the plantar surface of his left foot. The lesion bleeds with minimal trauma and you suspect a diagnosis of pyogenic granuloma. Which of the following would you expect to see on histologic examination? a. Jigsaw pattern of tumor cells in the dermis b. Basaloid cells with palisading nuclei c. Cuboidal cells within a highly vascularized stroma d. Proliferation of capillaries in an edematous stroma e. Epidermal hyperplasia, hyperkeratosis, and koilocytosis 9 The rate of lymphatic invasion of eccrine porocarcinoma is approximately: a.