Case Report and Review of Eccrine Porocarcinoma in Skin of Color

Skin cancers are often misdiagnosed or diagnosed late in skin of color (Fitzpatrick types 4-6) resulting in increased morbidity and mortality. Rare skin cancers such as Eccrine Porocarcinoma (EPC), which accounts for 0.005% to 0.01% of all epidermal skin neoplasms, are even less likely to be accurately diagnosed in skin of color. Misdiagnosis of EPC is common due to its resemblance to skin cancers such as SCC, BCC, melanoma, and presence of atypical cell types in histology. The lack of case reports of EPC in skin of color adds to the challenge of achieving an accurate and timely detection, diagnosis, and treatment in this patient population. The purpose of this research is to review case reports of EPC documented in skin of color, identify, and highlight salient clinical and histopathological characteristics of EPC in this patient population, and to describe an additional case of EPC in skin of color encountered in the clinic that was initially misdiagnosed as seborrheic keratosis.

Skin cancers are often misdiagnosed or diagnosed late in skin of color (Fitzpatrick types 4-6) resulting in increased morbidity and mortality. Rare skin cancers such as Eccrine Porocarcinoma (EPC), which accounts for 0.005% to 0.01% of all epidermal skin neoplasms, are even less likely to be accurately diagnosed in skin of color. 1 Misdiagnosis of EPC is common due to its resemblance to skin cancers such as SCC, BCC, melanoma, and presence of atypical cell types in histology. The lack of case reports of EPC in skin of color adds to the challenge of achieving an accurate and timely detection, diagnosis, and treatment in this patient population. The purpose of this research is to review case reports of EPC documented in skin of color, identify, and highlight salient clinical and histopathological characteristics of EPC in this patient population, and to describe an additional case of EPC in skin of color encountered in the clinic that was initially misdiagnosed as seborrheic keratosis.

METHODS
"Indigenous Peoples", "Middle Eastern" -as these tend to correspond with Fitzpatrick IV -VI types. Google scholar, PubMed, and Ovid MedLine Databases were used to search for articles. Case reports ranging from 1994 to present day were included in analysis.
We present a case of an 82-year-old African American male (Fitzpatrick type 5/6), who was referred to the Dermatologic Surgery Center of Washington for an enlarging nodule on the right lateral malleolus. Initial biopsy by the referring physician 3 years prior demonstrated a seborrheic keratosis. Past medical history was significant for bilateral kidney transplant 7 years prior secondary to diabetic nephropathy.
The cutaneous exam showed a 2 x 1.5 cm skin colored nodule with an erosive center on the right lateral malleolus (Figure 1).

Figure 1.
There was palpable inguinal lymphadenopathy but no cervical or axillary lymphadenopathy.
Pathology findings showed an exophytic lesion of skin with a well demarcated proliferation of atypical epithelial cells that emanated from the epidermis and extended into the dermis. This proliferation contained small duct-like structures within and resembled anastomosing wide bands of cells. Many epithelial cells were found to have enlarged, hyperchromatic, and pleomorphic nuclei surrounded by eosinophilic cytoplasm.
There are also atypical mitoses present and the neoplasm was surrounded by a prominent fibrovascular stroma ( Figure 2). Mohs surgery was performed with the tumor being cleared after 2 stages and there is no evidence of recurrence or metastatic disease at 10 months follow-up.
Robson et al. conducted one of the largest reviews of EPC, which contains 69 cases and offers a comparator dataset to this review. 1 Our review identified 12 additional cases of EPC described in patients of color whose ethnic origins included Japanese, Indian, Hispanic, and African American, making n = 13 with the present case. The cases as presented in Table 1, showed a slightly higher predilection in females (n=8) compared to differentiation, but malignant squamous cells, melanocytes, and clear cells were also present in many cases. 3 out of the 13 cases of EPC in skin of color were classified as "pigmented EPC", coined by Hara and Kamiya in 1995 to describe histology showing melanocyte symbiosis with tumor cells. Dendritic cells containing melanin stained positive for HMB-45 and S-100 whereas ductal tumor cells were reactive to markers such as CEA, CK-7 and non-reactive to S-100. Approximately 33% (n=4) patients of color had lymph node involvement, >7 mm depth of tumor invasion, and >14 mitoses per high power field, which are associated with poor prognosis in patients with EPC. This is higher than the 20% lymph node metastasis for EPC cases that Robson et. al report in their review.

RESULTS
The review of a small number of cases seem to suggest a more advanced EPC tumor presentation in patients of color than lighter skinned patients. This trend is similar to findings in melanoma which showed that Hispanic (26%) and Black patients (52%) had more advanced melanoma at presentation compared with Caucasian patients (16%). 2 The 33% lymph node metastasis observed in patients of color with EPC is higher than the rates of metastatic BCC in all races: 0.0028 to 0.55%, but similar to rates of metastatic SCC that develops within a chronic scarring process more seen in skin of color: 20-40%. 2 Clinicians should also be aware of atypical clinical and histological variants of EPC in people of color such as pigmented EPC, which can be confused for malignant melanoma. Misdiagnosis of EPC can have significant consequences given that the cancer has the potential to be aggressive. It is thought that 20% of EPC recur locally, an additional 20% metastasize, and mortality rates of 67% are seen when local lymph nodes are involved. 3 Therefore, the differential diagnoses of these lesions must be considered and ruled out using thorough dermatopathological analysis. Additional case details and a larger sample size are needed before determining diagnostic and treatment guidelines, mortality, and risk associated with EPC in skin of color.