The biopsy of papules from the left

The biopsy of papules from the left leg showed a parakeratotic column associated with eccrine ducts, appearing as cornoid lamella similar to porokeratosis and standing within an epidermal invagination. The cornoid lamella-like columns were composed of compact hyperkeratosis with underlying hypokeratosis. The granular layer was absent in this invagination, which contained vacuolated keratinocytes. The eccrine ducts in the dermis were significantly tortuous, dilated, hyperplastic, and some were full of sweat (Figure 2A). In addition, significant papillomatosis with irregular acanthosis and some inflammatory calcium ionophore around the invaginated epidermis were observed. No involved follicles were found. All these histopathological features were consistent with PEODDN. The histology of the ulcer showed poorly differentiated tumor nests with some atypical keratinocytes and necrosis in the dermis (Figure 2B). Atypical cells exhibited glassy eosinophilic cytoplasm, hyperchromatic nuclei, atypical mitoses, and disorganized architecture (Figure 2C). These features of the ulcer conformed to invasive SCC. The SCC lesion was surgically excised and no management of PEODDN was initiated because of the patient\'s refusal. Unfortunately, lymphatic metastasis of her left groin was found 8 months later (Figure 2D).
Discussion PEODDN is a rare hamartoma of the eccrine sweat glands first termed by Abell and Read in 1980. Recently, the term porokeratotic adnexal ostial nevus, which includes PEODDN and porokeratotic eccrine and hair follicle nevus (PEHFN), was proposed because some cases had involvement of both acrosyringia and acrotrichia histologically. The pathogenesis of PEODDN is still unclear. It has been suggested that PEODDN could be a congenital hamartoma of the acrosyringium and dermal duct. In a recent report, it was considered that PEODDN is a mosaic form of keratitis–ichthyosis–deafness syndrome with a gene mutation in GJB2 encoding a gap junction protein connexin 26 (Cx26). The lesions of PEODDN are usually present at birth. However, rare cases of late onset in adults had also been reported. The usual distribution of these lesions is the distal portion of a limb. A widespread distribution of PEODDN along Blaschko\'s line is a rare condition. The lesions are composed of small keratotic papules or comedo-like pits filled with keratotic plugs. The plugs usually arise vertically from the skin surface as multiple tiny filiform spines. In serious cases, the thornlike projections with larger plugs can be closely grouped and some of them can coalesce into hyperkeratotic verrucous plaques as in our case. It is usually asymptomatic, but there are a few cases with pruritus, anhydrosis, or hyperhidrosis. Usually, PEODDN is not associated with other diseases; however, its association with linear verrucous epidermal nevus has been described previously. PEODDN\'s association with Bowen\'s disease and SCC has been described in only two cases. Histologically, PEODDN displays some characteristic features. It shows cornoid lamellae-like columns of parakeratosis lying within the epidermal invaginations. The parakeratotic column similar to porokeratosis is the histologic pathognomonic for PEODDN and corresponds to clinically observed keratin plugs and filiform papules. It is also typical that the granular layer is absent in epidermal invagination, which contains some vacuolated and dyskeratotic keratinocytes. This parakeratotic column is almost always found overlying an eccrine duct with a dilated acrosyringium, but this condition is not always found. Furthermore, the eccrine duct in the dermis is often tortuous, dilated, and hyperplastic. The most important differential diagnosis for PEODDN is linear epidermal nevus, especially linear verrucous nevus and nevus comedonicus. Histological examination is helpful for their distinction. PEHFN has similar clinical manifestations with PEODDN, but the former has cornoid lamellae overlying both follicle and eccrine gland. The evolution of PEODDN can be stationary or progressive. So far, there are no ideal treatment options for PEODDN. Ultrapulse CO2 laser, erbium laser, and surgical excision can be reasonable options for relief of some lesions.