Eccrine Porocarcinoma Arising in Pre-Existing Eccrine Poroma

초록

Eccrine poroma is a benign adnexal tumor derived from the intraepidermal sweat duct epithelium. Eccrine porocarcinoma, on the other hand, is regarded as the malignant counterpart of eccrine poroma1 . Eccrine porocarcinoma can be oserved as an erythematous to violaceous nodule, papule, plaque, or tumor, most often arising on the lower extremities, followed by the head1,2. It occurs mainly in elderly patients, most frequently between the sixth and the eighth decade3 . A 61-year-old man presented with a solitary erythematous scaly plaque on his right dorsum of the foot for 2 years (Fig. 1A, B). There was no history of trauma in the area of the skin lesion, also the patient did not complain of any subjective symptoms. Punch biopsy showed uniformly small cuboidal tumor cells forming broad, anastomosing bands in continuity with the epidermis (Fig. 1C, D). Total excision for the residual lesion was recommended to the patient, but the patient refused. After 6 years, the patient revistied with an erythematous scaly plaque in the same region, with rapid growth over the past several months (Fig. 2A, B). Additionally, the patient complained of pain and spontaneous bleeding. Dermoscopy of the lesion showed predominantly round-tooval shaped pink structureless areas surrounded by a white-topink halo and polymorphous vessels (Fig. 2C). Histopathologic findings revealed a lobular infiltrative tumor composed of small cuboidal cells that extended into the dermis. Atypical neoplastic cells with hyperchromatic nuclei and some mitotic figures were observed (Fig. 2D∼F). Computed tomography of the chest and the abdomen showed no evidence of metastasis. Wide excision was performed, and there were no signs of recurrence after 14 months of follow-up. Eccrine porocarcinoma is an uncommon malignant adnexal cutaneous tumor deriving from the terminal cells of the intraepithelial part of the eccrine duct called the acrosyringium3 . Eccrine porocarcinoma can arise de novo or evolove from a benign long-standing eccrine poroma with a highly variable duration of years to decades1 . Although it has been reported that up to 18% of eccrine porocarcinoma come from eccrine poroma1,2, only two cases of eccrine porocarcinoma arising from eccrine poroma have been reported in the Korean literature4,5. Sudden clinical changes, such as rapid growth, ulceration, and spontaneous bleeding, suggest malignant degeneration1,2. Dermoscopy usually does not help in the differential diagnosis, as both eccrine poroma and eccrine porocarcinoma can present with a white-to-pink halo with polymorphous vessels1 . Histopathologic features such as atypical poroid cells with pleomorphic nuclei, increased nuclear-cytoplasmic ratio, a high rate of atypical mitotic activity, and infiltrating borders are indicative of eccrine porocarcinoma1,3. Local recurrence, lymph node metastasis, and distant metastasis occur in 20%, 20%, and 10% of cases, respectively2 . Considering the difficulty in diagnosing eccrine poroma with clinical or dermoscopic findings and the tendency for malignant transformation, it is advisable to perform a complete excision or close follow-up for eccrine poroma lesions, especially in elderly patients. Herein, we present an educational case of eccrine poroma showing progression to porocarcinoma with a clinical history of pain and a sudden increase in size.

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