Poromatosis: the occurrence of multiple eccrine poromas
Published Web Locationhttps://doi.org/10.5070/D37d14m946
Poromatosis: the occurrence of multiple eccrine poromasUniversity of California, Davis Department of Dermatology
Daniel Navi MD, Maxwell Fung MD, Peter J Lynch MD
Dermatology Online Journal 14 (1): 3
Eccrine poromas are rare, benign adnexal tumors derived from the intraepidermal portion of sweat ducts. Historically they were thought to arise from eccrine ducts although today it is thought that they may also have an apocrine origin. They usually appear as solitary, slow-growing, skin-colored papules on acral surfaces. Here we present the unusual situation of a patient with multiple poromas only three of which are located near the distal extremities.
|Figure 1. Erythematous papule on L ankle|
A 64-year-old man with multiple medical problems including non-Hodgkin lymphoma status-post treatment with chemotherapy with CHOP, and Rituxan, Conn syndrome, hypertension, and history of colorectal carcinoma presented to the dermatology clinic for evaluation of multiple bothersome lesions. The lesions included an irritated, pedunculated papule near his left nipple clinically suggestive of a skin tag (not shown) and a larger erythematous papule on his left ankle clinically similar in appearance to a skin tag or a pyogenic granuloma (Fig. 1). The lesions in question had been present for several months and would occasionally bleed when traumatized thus prompting the patient to seek care. Upon a complete skin examination, six additional flesh-colored papules were identified: three on patient's chest, one on his eyelid and two on his left forearm. One of the forearm lesions appeared irritated with surrounding post-inflammatory hyperpigmentation that the patient stated was the result of self treatment (Figs. 2 and 3). No regional lymph nodes were palpable for any of the lesions.
|Figure 2||Figure 3|
|Figure 2. Irritated, pedunculated papule with surrounding post-inflammatory hyperpigmentation on L forearm|
Figure 3. A closer, profile view of lesion in
Shave biopsies of the lesions on left ankle and left nipple were obtained to establish definitive diagnosis. Sections from both specimens showed lesions with a polypoid profile and slightly papillated surface composed of broad, interanastamosing strands of small monomorphous poroid epithelial cells and focal sweat ducts. This established the diagnosis of eccrine poroma for both lesions (Figs. 4-7). Focal glandular differentiation was also present in the lesion from the left chest. A later shave biopsy of one of the left forearm lesions was also consistent with the diagnosis of poroma. All lesions were treated with complete excision with no evidence of recurrence to date.
|Figure 4||Figure 5|
|Figure 6||Figure 7|
|Figures 4-7. Polypoid lesions from the left ankle (Figure 4, H&E, 20x) and left chest (Figure 5, H&E, 20x), both exhibiting poroid epithelial cells with focal sweat duct formation (Figures 6 and 7, H&E, 400x)|
Eccrine poroma (EP) is a benign sweat gland tumor comprising cells usually differentiating toward the intraepidermal portion of the eccrine sweat duct. First reported by Pinkus et al. in 1956 , these neoplastic growths are believed to comprise 10 percent of all sweat gland tumors, which of themselves represent only 1 percent of all primary cutaneous lesions . The predilection of these tumors for specific locations on the body has been somewhat controversial. The prevailing notion is that EPs arise primarily on hairless acral surfaces (i.e., hands and feet) and occurred because of the high concentration of eccrine sweat glands in those areas [3, 4]. However, a number of case series have demonstrated that head, neck, and trunk regions represent more common sites for EPs than traditionally believed [5, 6]. Indeed, of the six lesions diagnosed as EP in our patient only three were located on the distal extremities. Based on the reported cases there does not appear to be any sexual, racial, or familial predisposition for these lesions. Furthermore, EPs have been reported in all age groups with a peak incidence in the seventh decade of life .
Clinical diagnosis of EPs is often difficult because they exhibit a polymorphic gross appearance and may mimic lesions as diverse as pyogenic granulomas, skin tags, warts, cysts, and other adnexal tumors. Although they usually present as skin-colored papules or nodules less than 2 cm in diameter, pigmented poromas (from melanin) [9,10] and erythematous lesions (from dilation or proliferation of blood vessels) have been reported . Surface erosion or ulceration, presumably secondary to trauma, are occasionally reported. EPs almost always appear as solitary tumors and in those rare occurrences where they occur in clusters, groups or widely disseminated, are referred to as poromatosis . A review of the literature revealed very few reported cases of multiple poromas (i.e., poromatosis) and in no instances have poromas previously been reported as occurring in patients with non-Hodgkin lymphoma or chemotherapy [11, 12, 13, 14, 15].
The pathogenesis of EPs remains to be elucidated. In two of the reported cases the occurrence of multiple EPs were limited to previously irradiated cutaneous areas suggesting a role of radiation trauma in promoting the development of these tumors [14, 15]. However, the patient in this case report has not undergone prior radiotherapy. Although radiation [14, 15], other forms of trauma , and hormonal influences during pregnancy  have been suggested as potential pathogenic triggers for EPs, the reported cases where these factors are absent far outnumber those where clear associations have been noted.
The term poroma has been traditionally used to refer to glandular adnexal neoplasms of eccrine lineage, which includes the typical eccrine poroma as well as its three distinct histological subtypes. These subtypes display varying cellular growth patterns as follows: hidroacanthoma simplex, dermal duct tumor, and poroid hidradenoma . More recently it has been suggested that poromas may arise from both eccrine and apocrine sweat glands . The difficulty in differentiating the eccrine from apocrine lineage of poromas occurs because the sweat ducts of the two are histologically and immunohistochemically indistinguishable. Most reported cases of apocrine poroma exhibit the combination of sebaceous, apocrine, and follicular differentiation, which share the common embryogenic origin of the folliculosebaceous-apocrine unit .
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