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The Ohio State University Medical Center, Columbus, OH
43210
Riverside Radiological Associates, Columbus, OH 43214
The Ohio State University Medical Center, Columbus, OH
43210
A 60-year-old man with type 2 diabetes mellitus presented with a 3-year history of a painful mass in the mid plantar region of the left foot. The patient sought medical attention because during the previous 3 months, the pain and the size of the lesion had increased. His medical history was significant only for the surgical removal of a foreign body in 1991 from a different area of the body. At physical examination, a firm, moveable subcutaneous nodule measuring 1 cm was palpated on the plantar aspect of the foot. The overlying skin was intact. The area of the lesion was tender, but no induration or erythema was evident. The clinical diagnosis was plantar fibroma, and the patient underwent MR imaging.
MR imaging revealed a 1-cm mass in the subcutaneous tissue of the midfoot that was superficial relative to the medial plantar fascia. The tumor appeared to displace the plantar fascia rather than arise from it. The mass showed low signal intensity on T1-weighted images and intermediate to high signal intensity on T2-weighted and proton density—weighted images (Fig. 4A,4B,4C,4D). After IV administration of gadolinium, the tumor enhanced homogeneously. MR findings confirmed the clinical diagnosis of plantar fibroma.
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The patient underwent an excisional biopsy to remove the tumor, which measured 2 x 1 x 1 cm and was firm and tannish white. Microscopically, a collagenous pseudocapsule was observed. The predominant cell types were small basoloid or eosinophilic polygonal and fusiform. Mitotic activity was low, and immunohistochemical staining for cytokeratin showed positive results. No malignant features or necrosis was noted. The final histologic diagnosis was benign eccrine acrospiroma.
Eccrine acrospiroma, or hidradenoma, is a rare benign tumor of the sweat gland that typically is located in the superficial and deep dermis and occasionally in the subcutaneous tissue. The tumor arises from eccrine glands, a type of sweat gland that is distributed throughout the body. Clinically, the lesion is often a solitary nodule that can be as large as 2 cm and is usually covered by normal epidermis [1]. Cystic change, hemorrhage, and multinodularity have been reported, and pain may accompany these symptoms. The tumor has a predilection for developing in the distal extremities, but eccrine acrospiromas have also been described as occurring elsewhere in the body. Treatment is complete excision of the tumor [2].
Histologically, eccrine acrospiromas have a lobular architecture and are surrounded by a collagenous pseudocapsule [1]. The tumor is often composed of either small round cells with clear to palely colored eosinophilic cytoplasm or polygonal cells with basophilic cytoplasm. Cystic components can be present. When the predominant cell type is clear or vacuolated, the term "clear cell hidradenoma" is used [1]. Malignant variants are rare.
The MR imaging appearance of sweat gland tumors has previously been reported as a subcutaneous cystic mass or a multiocular cystic structure with a solid mural nodule [3, 4]. Fluid—fluid levels and hemorrhaging have also been described. Tumors reported in earlier studies had low signal intensity on T1-weighted images and high signal intensity on T2-weighted and short tau inversion recovery images. In our patient, we observed what we believe to be a previously unreported MR imaging appearance, a solid enhancing nodule. A sweat gland tumor should be considered in the differential diagnosis of a subcutaneous mass regardless of signal characteristics.
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  W. Jin, G. Y. Kim, B. L. Lew, D. M. Yang, H. C. Kim, J. K. Ryu, J. S. Park, and K. N. Ryu Sonographic Findings of an Eccrine Spiradenoma: Case Report and Literature Review J. Ultrasound Med., May 1, 2008; 27(5): 813 - 818. [Full Text] [PDF]
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 Y-D Han, Y Huan, J-L Deng, Y-G Zhang, and C H-S Zhang MRI appearance of multiple eccrine spiradenoma Br. J. Radiol., January 1, 2007; 80(949): e27 - e29. [Abstract] [Full Text] [PDF]
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