Introduction Eccrine spiradenoma (ES) is a rare benign adnexal tumor originating from the eccrine glands that was first described by Kersting and Helwig in 1956.1 ES typically presents as a single, solid, well-defined nodule of less than 1 cm in size, localized within subcutaneous tissue, but it can also present as one large nodule or as multiple nodules, and have a zosteriform, linear, blaschkoid, or nevoid distribution pattern. The tumor can occur in individuals of any age, although it typically affects young adults aged 15–35 years, and does not preferentially affect males or females.2 Most ES cases with multiple tumors have been reported on the scalp, face, or cervical regions.3 However, a solitary lesion occurring on the forehead region is rare. Here, we report such a case in a 38-year-old woman, which may enrich the clincial presentation of this disease of clinician. Case report A 38-year-old woman presented with a 10-year history of a small nodule on her forehead in the Hospital for Skin Diseases (Institute of Dermatology) in May, 2018. The lesion had gradually undergone a mild increase in size over the past 10 years, with the occasional presentation of paroxysmal pain. There were no specific findings in the patient's family history and medical history. Upon examination, a single soft and tender nodule measuring 0.3 cm × 0.4 cm was noted (Fig. 1A). We performed a complete resection of the tumor, and histopathological examination at low power showed a deep, well-defined, and encapsulated tumor nodule in the dermis (Fig. 1B). At higher magnifications, two distinctive cell types were observed: large pale cells with ovoid vesicular nuclei and small, dark, basaloid cells with hyperchromatic nuclei. Moreover, small lymphocytes scattered between tumor cells were observed (Fig. 1C). In the lumina, periodic acid–Schiff stain (PAS)-positive eosinophilic tubular material was noted (Fig. 1D).Figure 1: Clinical and histopathological results of the patient. (A) Image of the solitary, soft nodule on the forehead, measuring 0.3 cm × 0.4 cm. (B–D) Histopathological results. B: The deep, well-defined, encapsulated tumor nodule arising from the dermis (H&E, ×80). (C) The two types of cells (small, dark, basaloid cells with hyperchromatic nuclei, and cells with large, pale, vesicular, and ovoid nuclei) in the nodule (H&E, ×400). (D) Tubular formations with PAS-positive eosinophilic amorphous material in the lumina (PAS, ×600).The diagnosis of ES was made based on the histological results. The patient has been followed up since diagnosis, and no recurrence had been observed at the time of writing this report. Discussion ES is a rare benign soft tissue cancer, typically presenting as a tender, painful, rounded, bluish, dermal nodular lesion. It is usually found in the deep dermal layer and composed of multinodular tumors with basophilic lobules encapsulated by thick connective tissue. The tumor cells can be divided into two types: cells with low-density cytoplasm located at the center of the tumor and small dark cells with high-density cytoplasm in the perimeter of the tumor. Cystic spaces or tubular structures also can be observed.4 ES mainly occurs on the upper ventral aspect of the body and appears as a solitary tumor.2 In recent solitary cases reported, ES occurred more commonly in the upper extremity.2,5,6 However, a solitary lesion occurring on the forehead region, as in this case, is rare presentation. Clinically, an ES tumor often presents with pain, so this type of tumor needs to be differentiated from other painful skin tumors such as glomus tumor, angioleiomyoma, neuroma, dermatofibroma, angiolipoma, neurilemmoma, and granular cell tumor. Additionally, ES should be differentiated from cylindroma using histology. Cylindroma is a benign tumor, also derived from the eccrine glands, composed of small tumor cell aggregations that are differentially polymorphic in shape and arranged in a jigsaw puzzle pattern. Moreover, a cylindroma tumor mass is rimmed by eosinophilic basement membrane-like material. ES is sometimes similar to hemangiomas and glomus tumors; however, these tumors contain blood in the vascular lumen and have no ducts.7,8 Although a few cases of malignant change in ES have been reported, it occurs very rarely, and most patients have a good prognosis. Long-standing ES tumors tend to deteriorate. In contrast, if the tumor suddenly and rapidly increases, hemorrhages, and ulcerates, the possibility of malignant transformation should be considered. Thus, early and complete surgical excision is the preferable diagnostic tool and treatment option for ES.9 In conclusion, we reported a 38-year-old woman with ES on the forehead region, which is a rare presentation. Nowadays, complete resection of the ES should be considered as a preferable option.