Growing Asymptomatic Nodule on the Ear.

A 56-year-old Caucasian woman presented with a lesion on the right ear of 5-year duration. The site had undergone incision and drainage with no expression of contents followed by a complete excisional punch biopsy 4 years prior to presentation. The patient now presented with recurrence of the lesion, which she reported had been growing in size. Despite its growth, the lesion remained asymptomatic. Physical examination revealed a dermal nodule with a bluish hue and visible telangiectasias on the root of right ear, measuring 1.7 cm in size [Figure 1]. Histopathologic evaluation of a biopsy revealed a dermal-based, well-circumscribed lobulated tumor island composed of basophilic cells with little cytoplasm [Figure 2a]. Higher magnification showed two types of tumor cells – small, dark basaloid cells with scant cytoplasm and small nuclei and slightly larger cells with a more open nuclear chromatin pattern [Figure 2b]. The larger cells surrounded areas of focal ductal differentiation. No atypical features were identified.

Figure 1

Dermal nodule with a bluish hue and visible telangiectases on the right root of the ear

Figure 2

(a) Well-circumscribed lobulated tumor island composed of basophilic cells with little cytoplasm (H and E, original magnification ×20). (b) Close inspection revealing two cell types – small, dark basaloid cells with scant cytoplasm and slightly larger cells with a more open nuclear chromatin pattern. Scattered lymphocytes and hyaline deposits are noted in the tumor nodules (H and E, original magnification ×200)

Answer

Diagnosis: Spiradenoma.

Discussion

Spiradenomas are well-differentiated, benign dermal neoplasms originating from the sweat glands. They usually present as small solitary nodules that can grow up to several centimeters, typically with a blue, gray, or purple hue and are often strikingly painful in nature.[1] Spiradenomas typically arise on the head, neck, and trunk; however, cases in other areas such as the breast have been reported. Cases of multiple linear, zosteriform, blashkoid, and nevoid spiradenomas have also been reported. It is not uncommon for spiradenomas to occur concomitantly with cylindromas, trichoepitheliomas, and/or trichoblastomas. In particular, patients with Brooke–Spiegler present with multiple spiradenomas, cylindromas, and trichoepitheliomas caused by mutations in the CYLD gene.[2]

Histologically, spiradenomas show one or more large, sharply demarcated basophilic nodules of the dermis. Two types of cells are seen in the nodules – small, dark, basaloid cells with hyperchromatic nuclei and cells with larger, pale, ovoid nuclei, which tend to be toward the center of the lesion. Duct-like structures and cystic cavities may be seen. The cystic cavities are usually filled with finely granular eosinophilic material that is diastase resistant and periodic acid-Schiff positive. Historically, spiradenomas were thought to be of eccrine lineage, though many lesions have been shown to demonstrate apocrine differentiation.[3] Clinically, there have been no reported cases on acral skin, further questioning their eccrine origin. Spiradenomas are histologically closely related to cylindromas, often displaying foci of decapitation and tubular patterns with uninterpretable differentiation. Immunohistochemical analysis of several spiradenomas and cylindromas found similar expression patterns of S-100 in the large, pale-staining cells, pointing to eccrine differentiation, and human milk fat globulin (HMFG) and lysozyme in the tubular cells, associated with apocrine differentiation.[4] Classically, spiradenomas also stain positive with CK7, epithelial membrane antigen, and carcinoembryonic antigen, as well the myoepithelial stains p63 and SMA.

The pathogenesis of the formation of spiradenomas has not been completely elucidated. Derangements in intercellular bridge proteins that maintain epithelial organization, such as claudin-4, cadherin, and β-catenin, have been suggested as contributing to neoplasm formation. A study of 48 adnexal tumors found intense nuclear immunoreactivity for β-catenin in spiradenomas, in addition to pilomatricomas, suggesting a role of alterations in the β-catenin pathway in the development of spiradenomas.[5] This finding was corroborated in a study by Rajan et al., which also showed that a transition between cylindromas and spiradenomas can occur in patients with CYLD gene mutations.[6]

Although spiradenoma is considered to be a benign adnexal neoplasm with low recurrence rate, malignant transformation can occur in longstanding lesions, more commonly in patients over the age of 50. Increased expression of p53 has been observed in malignant spiradenomas, although the significance in the pathophysiology is unclear. Malignant spiradenomas tend to be aggressive tumors with high rates of metastasis and mortality; therefore, conservative surgical excision of spiradenomas is recommended.[7] Given the history of recurrence and growth in size, we recommended conservative management with complete surgical excision of the tumor in our patient, which she agreed to. There has been no evidence of recurrence to date.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.