Eccrine Poroma and its malignant variant
- Ivan Bristow
- 1 day ago
- 5 min read
Background
The eccrine poroma is an uncommon benign adnexal tumour (literally meaning appendage tumour) which arises from the epithelial lining of the sweat duct as it passes through the epidermis (known also as the acrosyringium). Consequently, it is commonly seen in areas where the sweat glands are most abundant - predominantly on the soles and palms, but it can occur elsewhere on the skin where there are sweat glands (such as the chest, back and neck). The patient is typically middle to old age and EP shows equal predilection for both sexes and skin types.
What does Eccrine Poroma look like?
First described by Pinkus in 1956 [1], the eccrine poroma in its classic form a firm, solitary, dome shaped papule, plaque or nodule, which maybe slight pedunculated and up to 2cms in diameter [2] but there can be considerable variability in appearance. EP is often pink or red in colour but occasionally has been reported as white or blue. The surface may be shiny and red leading to suspicion of a pyogenic granuloma.
However, pigmented lesions have been reported [3]. The lesion surface is often smooth although can be scaly, verrucous or rarely ulcerative [4]. The lesion typically has no symptoms, but occasional itching has been reported and bleeding following physical trauma to the lesion. The aetiology of EP is unclear but UV, trauma, radiation and HP virus have been suggested [5].
Dermoscopy of Poroma
The dermoscopy of EP has been evaluated with few consistent features, although one paper reviewing 13 cases with a dermatoscope reported consistently polymorphous blood vessels arrangements with a frequent “chalice-like” pattern to the terminal areas of the vessel. Pink-white and yellow structureless areas were also common on lesions [2, 6]. In darker skin types, clod vessels, coiled vessels, white lines, ulceration, the fibre sign (where clothes fibres adhere to the exudate from lesions, scales, and structureless areas were more common in patients with darker skin phototypes [7]. Around 25% of poroma lack any specific pattern [6]. Ultimately, dermoscopy can be helpful although were there is doubt excisional biopsy is required to establish the diagnosis.
Diagnosis
Classically presenting lesions are often diagnosed visually but in atypical lesion presentations diagnosis is often delayed – its highly variable appearance requires careful assessment to rule out many other malignant and benign causes. These lesions may resemble pyogenic granulomas, dermoid cysts, skin tags, verrucae, seborrheic keratosis, fibromas, melanomas, adnexal cysts, vascular tumours, basal cell carcinoma, and squamous cell carcinoma [8]. Where there is doubt, a biopsy is required to confirm the diagnosis. Treatment is straightforward with surgical excision.
The Porocarcinoma
A malignant variant of the EP is the Malignant Eccrine Poroma (MEP) or the more commonly termed "Eccrine Porocarcinoma" (EPC) first described by Pinkus in 1963 [9]. These are extremely rare – less than 0.1% of all cutaneous malignancies [10]. Like its benign counterpart (EP), it is most often seen on the lower extremity but is occasionally observed elsewhere. According to a large database survey the porocarcinoma affects older adults (mean age 66 years) – with around 32% on the lower limb and foot [11]. Lesions are often longstanding, ulcerated tumours and can be large. One review suggesting time from tumour appearance to diagnosis can be around 5-9 years or longer [12].
Studies have suggested the EPC may arise de novo or from malignant transformation of a longstanding EP - 18% of porocarcinoma in one dermatopathology review showed continuity from a pre-existing benign lesion [13]. Diagnostically, such lesions are a challenge as EPC may look similar to benign EP and their differential diagnoses but evolve into larger verrucous or ulcerative lesions over time [14].
Specialist histological staining following biopsy helps to discern EP from EPC along with specific genomic mutations which have now been identified.
Prognosis
The biological behaviour of the EPC is variable and unpredictable – partly because of its rarity and long term follow up data. As with all malignancies, early diagnosis improves the prognosis. However, studies report an approximately 20% potential for local recurrence, 20% for regional lymph node metastasis and 10% for distant metastasis [12]. One study showed that the presence of lymph node metastasis was associated with 1-year and 3-year overall survival of 88.9% and 39.5%, respectively [13].
Implications for podiatrists
Eccrine poroma is not an uncommon diagnosis for podiatrists. It is likely that in its classic form diagnosis and treatment should be straightforward. Statistically, its malignant variant, the EPC is extremely rare – based on probability melanoma, squamous cell carcinoma, basal cell carcinoma are much more likely to walk into the podiatry clinic. Either way, any suspicious lesion would warrant immediate referral.
In a review of 515 pedal tumours presenting at one hospital site (see my earlier blog here), 211 were malignant and none were EPC. Melanoma and squamous cell carcinoma accounted for over 90% of skin malignancies on the foot [15].
Ultimately, as with all unusual lesions, suspicion should prevail. The CUBED acronym can be helpful in highlighting which lesions should be referred for second opinions when there is any doubt.
References
1. Pinkus H, Rogin JR, Goldman P: Eccrine Poroma: Tumors Exhibiting Features of the Epidermal Sweat Duct Unit. AMA Archives of Dermatology 1956, 74:511–521.
2. Espinosa AE, Ortega BC, Venegas RQ, Ramírez RG: Dermoscopy of non-pigmented eccrine poromas: study of Mexican cases. Dermatol Pract Concept 2013, 3:25–28.
3. Alfredo MAC, Lai MRR, Miot LDB, Haddad GR, Garcia AL, Miot HA: Pigmented eccrine poroma in an atypical location. An Bras Dermatol 2022, 97:624–627.
4. Sawaya JL, Khachemoune A: Poroma: a review of eccrine, apocrine, and malignant forms. Int J Dermatol 2014, 53:1053–1061.
5. Johnson RC, Rosenmeier GJ, Keeling JH, 3rd: A painful step. Eccrine poroma. Arch Dermatol 1992, 128:1530, 1533.
6. Marchetti MA, Marino ML, Virmani P, Dusza SW, Marghoob AA, Nazzaro G, Lallas A, Landi C, Cabo H, Quiñones R, et al: Dermoscopic features and patterns of poromas: a multicentre observational case–control study conducted by the International Dermoscopy Society. J Eur Acad Dermatol Venereol 2018, 32:1263–1271.
7. Akay BN, Erol Mart HM, Okcu Heper A: Dermoscopic Features of Eccrine Poromas in Diverse Skin Phototypes: A Retrospective Study of 26 Cases. Dermatol Pract Concept 2025, 15:5071.
8. Mishra N, Chew DEM, Wong KPL, Bin Zainuddin MA: Eccrine Poroma of the Palm: A Case Report and Literature Review. Cureus 2024, 16:e69489.
9. Pinkus H, Mehregan AH: Epidermotropic Eccrine Carcinoma: A Case Combining Features of Eccrine Poroma and Paget's Dermatosis. Arch Dermatol 1963, 88:597–606.
10. Bartoš V, Kullová M: Eccrine Porocarcinoma: A Case Report of a Rare Skin Malignancy (Dermatopathologic View). Galician Medical Journal 2017, 24:E201711.
11. Behbahani S, Malerba S, Karanfilian KM, Warren CJ, Alhatem A, Samie FH: Demographics and outcomes of eccrine porocarcinoma: results from the National Cancer Database. Br J Dermatol 2020, 183:161–163.
12. Tsiogka A, Koumaki D, Kyriazopoulou M, Liopyris K, Stratigos A, Gregoriou S: Eccrine Porocarcinoma: A Review of the Literature. 13 2023:1431.
13. 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. The American Journal of Surgical Pathology 2001, 25.
14. Park J, Kwon H, Cho MK, Park YL, Lee SY, Lee JS, Whang KU: A Case of Malignant Eccrine Poroma Developing on the Suprapubic Area. Annals of dermatology 2008, 20:37–40.
15. Park HK, Choi YD, Yun SJ: Clinical characteristics and differences of 802 acral tumours, categorized by anatomical sites. Clin Exp Dermatol 2022, 47:312–318.
