Razi Journal of Medical Sciences

    Introduction: Microcystic adnexal tumor is a rare sclerosing variant of ductal carcinoma of eccrine sweat gland which is deeply invasive. This tumor which is said to have high recurrence rate is often misdiagnosed as other benign or malignant skin lesions and improper treatment is administered. Case Report: We report herein a 59-year-old man who underwent incisional biopsy for a congenital lesion on posterior neck which had grown recently. Microscopic examination exhibited an infiltrative tumor constituted by small cord-like and angulated tubules with tadpole or comma-like shapes, individually set in abundant fibrous stroma in dermis. So the diagnosis was syringoma. In the next step, the lesion underwent excisional biopsy. Histologic examination noted a tumor in dermis with extension to subcutis which contained basaloid keratinocytes with occasional horn cysts and abortive hair follicles. In other areas, ducts and gland-like structures lined by two-cell layers predominated. The tumor had extended to skeletal muscle and perineurial structures, but no significant atypia or mitosis was identified. Eventually, with respect to the above-mentioned features, the diagnosis was microcystic adnexal tumor. Conclusion: It seems useful to report this case since correct diagnosis of this rare invasive skin tumor and proper use of Mohs’ surgery lead to a significant decrease in recurrence rate. In this reported case, the noticeable point was that this tumor was set in a congenital lesion.