An Eccrine Porocarcinoma with Bowenoid Features on the Neck

Abstract

CASE REPORT An 80-year-old male visited our outpatient clinic with the presence of a progressively enlarging eczematous plaque over the right neck close to the post-auricular area for 2 years. The skin lesion was unresponsive to cryotherapy and topical steroids. At this presentation, the physical examination revealed a ten dollar coin-sized, polygonal, salmonred firm plaque with erosions and crusts, accompanied with a pinkish small nodule which was located in the center of the plaque (Fig. 1). Under the suspicion of chronic eczema or deep fungal infection, we performed a skin biopsy. The pathology revealed a malignant neoplasm of skin composed of pleomorphic basaloid and squamoid cells with frequent mitoses and apoptosis. The tumor was epidermal-based with dermal extension and anastomosing tumor cords showing multiple connections to the epidermis (Fig. 2A, 2B). Ductal differentiation is seen and can be accentuated under both epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA) stains (Fig. 2C, 2E). Taken together, an eccrine porocarcinoma (EP) was diagnosed. The patient received a wide local excision thereafter. The pathology reported eccrine porocarcinoma with bowenoid features. Focal en mass necrosis (Fig. 2D), focally infi ltrative border, ductal differentiation, and intracytoplasmic lumina. Squamous differentiation was also noted. There were frequent mitoses (>30 per 10 HPFs) and perineural invasion, without evidence of lymphovascular invasion. The mainly pushing advancing behavior and focal dyskeratosis were characteristic of bowenoid pattern. The post-operative course was smooth and there was neither recurrence nor evidence of metastasis in eleven months of follow-up to date. EP was first described by Mishima an Morioka in 1969 as a malignant counterpart of eccrine poroma, with both neoplasms putatively arising from the intraepidermal portion of the eccrine sweat duct or acrosyringium. Since then about 200 cases of EP have been reported in the literature, but there have been few large series. The tumor either arises spontaneously or develops in a longstanding eccrine poroma. Although often red and papular, the lesion can be flesh-colored or appear as a plaque, polypoid or verrucous lesion or as an ulcer, which sometimes bleed with minor trauma. Unlike benign eccrine poroma, which is often found on the palms and soles, most eccrine porocarcinomas arise on the lower extremity with the trunk and head also representing common sites, and the least common being on the palm and neck. The histologic diagnosis of EP was predicated on the basis of an irregular tumor at least partly formed of characteristic poromatous basaloid epithelial cells displaying ductal differentiation, and significant cytologic atypia. Most of them contained mature well-formed eccrine ducts having an eosino-