CORRECT DIAGNOSIS:
Eccrine porocarcinoma
DISCUSSION:
Eccrine porocarcinoma (EPC) is an extremely rare malignancy of the intraepidermal eccrine sweat gland (acrosyringium). There are less than 300 cases reported in the literature. The average age of presentation is 70-years-old. EPC is most commonly found on the lower extremity (50%), trunk (24%), head (18%), and upper extremity (8%). Its clinical presentation is highly variable, and it may manifest as a polypoid, keratotic, or ulcerated papule, nodule, or plaque. Due to this clinical variability, it is often misdiagnosed preoperatively.
EPC behaves aggressively and frequently metastasizes. The locoregional disease develops in 20% of patients, while distant visceral or osseous metastasis occurs in 10%. The 5-year survival is 78.3% after surgical excision with or without adjuvant radiation therapy. Prognosis depends on clinical and histologic factors. Clinically, the prognosis is worse with multi-nodularity, ulceration, or rapid growth. Histologically, the prognosis is worse with lymphovascular invasion, a high mitotic index (> 14 per high-power field), or tumor depth > 7 mm. Poor prognostic signs in our patient include the presence of ulceration, rapid growth, and possibly tumor depth > 7 mm.
Due to the rarity and aggressive natural course, optimal management of EPC remains unclear. Currently, wide local excision with 2 – 3 cm surgical margins seems to be most widely utilized; this leads to a cure rate of 70 – 80%. A recent review by Song et al. summarized 21 cases of EPC treated with Moh micrographic surgery that showed no local recurrences. One of the 21 cases demonstrated regional lymphatic metastasis, possibly representing in-transit disease at the time of Mohs micrographic surgery. Sentinel lymph node biopsy is controversial. Compromised immunity may be a risk factor for developing EPC. Upon literature review, 6 previous cases of EPC in immunosuppressed patients have been described. Of those, 3 patients had renal transplants, 2 patients were positive for human immunodeficiency virus infection, and 1 patient had chronic lymphocytic leukemia.
Our case has several unique features. First, the scalp is a less common location for EPC to present. Second, our patient is the 22nd case of EPC managed with Mohs micrographic surgery. Finally, our patient is the 7th reported case of EPC with compromised immunity, and, to our knowledge, the first case in a patient with lung transplantation.
TREATMENT:
The tumor was removed completely in 3 stages of Mohs micrographic surgery. Subsequently, the patient consulted with a medical oncologist who recommended no further workup aside from clinical surveillance. The patient is currently disease-free at the 3-month follow-up.
REFERENCES:
Bolognia, J. L., Jorizzo, J. L., & Schaffer, J. V. (2012). Dermatology (3rd ed.). Elsevier. pp. 539-544.
Mahomed, F., Blok, J., & Grayson, W. (2008). The squamous variant of eccrine porocarcinoma: A clinicopathological study of 21 cases. Journal of Clinical Pathology, 61(3), 361-365. https://doi.org/10.1136/jcp.2007.050081 [PMID: 18250063]
Song, S. S., Lee, W. W., Hamman, M. S., & Jiang, S. I. B. (2015). Mohs micrographic surgery for eccrine porocarcinoma: An update and review of the literature. Dermatologic Surgery, 41(3), 301-306. https://doi.org/10.1097/DSS.0000000000000140 [PMID: 25413495]
Mills, S. E. (2007). Histology for Pathologists (3rd ed.). Lippincott Williams & Wilkins.
Salgado, M. A. V., Garcia, C. G., Martin, J. A. L., Guerra, E., Benito, A., Sepulveda, J. M., & Carrato, A. (2010). Porocarcinoma: Clinical evolution. Dermatologic Surgery, 36(2), 264-267. https://doi.org/10.1111/j.1524-4725.2009.01562.x [PMID: 20042688]
Robson, A., Greene, J., Ansari, N., et al. (2001). Eccrine porocarcinoma (malignant eccrine poroma): A clinicopathologic study of 69 cases. American Journal of Surgical Pathology, 25(6), 710-720. https://doi.org/10.1097/00000478-200106000-00001 [PMID: 11314061]
Avraham, J., & Maker, A. (2012). Society of Surgical Oncology (SSO) 65th Annual Cancer Symposium: Abstract 7. Presented March 23, 2012.
Additional Comment: EPC is a rare skin tumor derived from the acrosyringium and is most frequent on the legs. Our patient presented with EPC in a less common location perhaps secondary to his immunosuppression for double lung transplant. Although ideal treatment for EPC has not yet been defined, Mohs micrographic surgery may be a promising approach.
