# Radiation Oncology/Porocarcinoma

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Porocarcinoma

## Overview

* Rare malignant tumor arising from the intraepidermal portion of the eccrine sweat gland duct epithelium; there are several histologic varieties
* May arise from preexisting benign eccrine poroma, with increase in size, tenderness, and sometimes odor
* ~300 cases reported in the literature; incidence estimated at 1 in 25,000 skin biopsies
* Most often occurs in the elderly, age at diagnosis 60-80 years
* Risk factors may include exposure to UV light, immunosuppression, and prior RT
* Distribution appears to have no correlation with sweat gland density: ~50% lower extremities, ~20% H&N and upper extremities, ~12% trunk and abdomen
* Can show early invasion of dermal lymphatics and multiple epidermotropic metastases
* Has metastatic potential (~20%), and poor prognosis once metastatic
* Treatment of choice is wide local excision; lymph node dissection beneficial, since ~50% can experience local recurrence and/or LN disease
* There are only a couple of reports using adjuvant RT; dose given ranges 55-70 Gy

## Literature

* Witwatersrand; 2007 (South Africa) PMID 17704263 -- "The squamous variant of eccrine porocarcinoma: a clinicopathological study of 21 cases." (Mahomed F, J Clin Pathol. 2007 Aug 17; [Epub ahead of print])
** Retrospective. 21 cases with squamous differentiation. Equal gender. Mean age 61.5 years. Average size 4.6 cm, 48% occurred in Black patients. 53% in extremities. 7 patients other skin tumors, 3 patients renal transplant
** Outcome: LR in 1/21, LN recurrence 1/21, 2/21 both LR+LN; 2 ultimately developed DM
* Nottingham; 2006 (UK) PMID 16638385 -- "We present an unusual case of eccrine porocarcinoma in that diagnosis was delayed for many years after the initial lesion appeared, resulting in relatively large tumor." (Affleck AG, Dermatol Online J. 2006 Jan 27;12(1):17.)
** Case report
* MSKCC; 1971 (1934-1969) PMID 5100098 -- "Sweat gland carcinoma: a clinico-pathologic study of 83 patients." (el-Domeiri AA, Ann Surg. 1971 Feb;173(2):270-4.)
** Retrospective. 83 patients. Gender comparable. Most common 50-70. Most <5cm, largest 15cm. Present >5 years in 23% patients. Prior RT: 8/83 (10%), range 6-40 years later. Treated with 48% WLE, 36% initial/subsequent LND, RT in 6% with widespread/metastatic disease
** Outcome: LN: 15% initially positive; additional 28% developed LN+ after primary treatment, but 20% had recurrent local disease prior to LN+. DM in 68%, vast majority had LN+ first. 5-year DFS 38%
** Conclusion: WLE appropriate only in low-grade disease, should do LND. Tumor considered radio-resistant

## RT Literature

* Spain; 2003 PMID 14725669 -- "Metastatic eccrine porocarcinoma: a 5.6-year follow-up study of a patient treated with a combined therapeutic protocol." (Gonzalez-Lopez MA, Dermatol Surg. 2003 Dec;29(12):1227-32.)
** Case report; right thigh and inguinal nodes, two separate RT treatments for complete local control
** RT used 55 Gy (Co-60 to 45 Gy AP/PA, followed by 10 Gy electron boost)
* Brussels; 2002 (Belgium) PMID 11937963 -- "[Eccrine porocarcinoma with extensive cutaneous metastasis] [Article in French]" (Ghislain PD, Ann Dermatol Venereol. 2002 Feb;129(2):225-8.)
** Case report. Metastatic lower leg
** RT used successfully for palliation of lymphedema symptoms
* Louisville; 1996 PMID 8812539 -- "Vulvar eccrine porocarcinoma." (Katsanis WA, Gynecol Oncol. 1996 Sep;62(3):396-9.)
** Case report; vulvar neoplasm with 2cm inguinal LN+
** RT used 50.4 Gy whole pelvis and 60 Gy inguinal region
* Munster; 1993 (Germany) PMID 8463101 -- "[Metastasizing eccrine porocarcinoma] [Article in German]" (Langfritz K, Hautarzt. 1993 Mar;44(3):176-9.)
** Case report; left leg with metastatic skin noduls
** RT with fast neutrons and Co-60 resulted in partial regression; death from tumour cachexia
* Arizona; 1990 PMID 2156600 -- "The role of radiotherapy in the treatment of malignant sweat gland neoplasms." (Harari PM, Cancer. 1990 Apr 15;65(8):1737-40.)
** Case report, 3 patients. Surgery + RT 70 Gy to surgical bed + 50 Gy to regional lymphatics.
** Outcome: 2 DFS at 27 and 35 months, 1 dead of systemic disease
* Germany; 1987 PMID 2820158 -- "[Eccrine porocarcinoma (malignant eccrine poroma)--a follow-up study] [Article in German]" (Doring HF, Z Hautkr. 1987 Jul 15;62(14):1051-2, 1055.)
** Case report; recurrent disease treated with RT, death
* 1986 PMID 3771857 -- "Radiation therapy and chemotherapy in malignant sweat gland tumors." (Whittington R, J Am Acad Dermatol. 1986 Nov;15(5 Pt 2):1093-7.)
** Case report; adnexal skin. Incomplete resection, with CR after EBRT