October 2009

Fig.2

Fig.3

Fig.4

Diagnosis: Porocarcinoma

Histology: Histopathological evaluation revealed nests of cuboidal, pale monomorphous cells (Figs. 2,3).   Nuclear pleomorphism and atypical mitotic figures were present (Fig. 4).  The tumor forms duct-like lumina (Fig. 3).  The epithelial nests are sharply demarcated from adjacent keratinocytes.  Porocarcinoma is cytokeratin, CEA and epithelial membrane antigen positive.

Clinical Course: After biopsy confirmed the diagnosis of porocarcinoma, the lesion was treated with wide local excision.  Margins were negative, and the lesion has not recurred.

Discussion:

Porocarcinoma is a rare malignancy of eccrine sweat gland that mainly presents in the elderly population (average age at diagnosis is 67 years).  It was first described in 1963 by Pinkus and Mehregan as epidermotropic eccrine carcinoma.  They typically arise on the lower extremities (44%), but are also reported on the trunk (24%), head (18%), and upper extremities (14%).  The most common presentation is an ulcerated, red, dome-shaped nodule with a shiny surface.  Clinical differential diagnosis include squamous cell carcinoma, basal cell carcinoma, verruca vulgaris, amelanotic melanoma, and pyogenic granuloma, and metastatic adenocarcinoma.

Porocarcinoma may develop de novo or within a preexisting poroma.  It arises from the intra-epithelial portion of the eccrine sweat duct.  From here it often invades the papillary dermis and dermal lymphatics.  The tumor may re-invade the epidermis, leading to cutaneous metastases and epidermotropic deposits.  Approximately 20% of porocarcinomas recur, and 20% will metastasize to regional lymph nodes. The mortality rate reaches 70% in patients with lymph nodes metastases.  Although rare, the occurrence of distant metastases has been reported.

Mutation of the p53 gene with loss of its suppressor function has been reported with malignant transformation.  P53 protein expression has been observed in both eccrine poromas and porocarcinomaThe diagnosis of porocarcinoma should always be considered in the differential diagnosis of a moist exophytic tumor, especially in the elderly. The treatment of choice is a wide excision of the primary tumor with histologically proven free margins.  A wide excision is curative in 70-80% of cases.  Metastatic porocarcinoma has been reported to be responsive to multiple treatment regimens, including radiation therapy and chemotherapy.

References:

1. Akalin T, Sen S, Yuceturk A, Kandiloglu G. p53 protein expression in eccrine poroma and porocarcinoma. Am J Dermatopathol, 2001,Vol. 23, No 5.

2. Akiyoshi E, Nogita T, Yamaguchi R, et al. Eccrine porocarcinoma. Dermatologia 1991; 40:182-210

3. Orella JAL, Penalba AV, San Juan CC, Nadal RV, Morrondo JC, Alvarez TT. Eccrine porocarcinoma- report of nine cases. Dermatol Surg, 1997; 23:925-28.

4. Pinkus H, Mehregan AH. Epidermotropic eccrine carcinoma: a case combining features of eccrine poroma and PagetÕs dermatosis. Arch Dermatol 1963; 88:597-607.

5. Robson A, Greene J, Ansari N, Kim B, Seed PT, McKee PH, Calonje E. Eccrine porocarcinoma (Malignant Eccrine Poroma), A clinicopathological study of 69 cases. Am J Surg Pathol, 2001,25(6): 710-720.