Acrospiroma

Abstract

Malignant eccrine acrospiromas are rare. Clinically, they resemble other cutaneous lesions. A high index of suspicion must be maintained in cases of histologically benign eccrine acrospiromas for three reasons: (1) malignant transformation can occur, (2) the presence of both benign and malignant tissue can lead to afalse-negative diagnosis if only the benign component is obtained in the biopsy specimen, and (3) benign-appearing tumors can recur locally or metastasize. The primary treatment is wide local excision with or without lymph node dissection. The efficacy of adjuvant chemotherapy and radiation therapy requires further investigation. We describe a case of malignant eccrine acrospiroma in an 80-year-old man, and we review the literature on this tumor, with emphasis on the differential diagnosis.

Introduction

A malignant eccrine acrospiroma (MEA) is a rare cutaneous tumor. These malignancies are believed to originate in the sweat glands because of their strong reaction to eccrine enzymatic stains and their ultrastructural features seen on electron microscopy. (1) An MEA is also known as a malignant clear-cell hidradenoma, clear-cell hidradenocarcinoma, and malignant nodular hidradenoma.

Although malignant acrospiromas can occur in all regions of the body, they are slightly more common on the head and neck (30%) and on the anterior trunk. (2-4) Clini cally, both malignant and benign eccrine acrospiromas are painless, solitary, and firm dermal masses whose color varies (flesh-toned, red, blue, or brown). (1,2,5) Therefore, they cannot be distinguished by their clinical appearance alone.

Although benign acrospiromas have been widely reviewed, reports of their malignant counterparts are rare. In this article, we describe a case of MEA, and we review the literature on this topic.

Case report

An 80-year-old black man came to the outpatient otolaryngology department with a 20-year history of a slowly growing lesion on the central scalp. He reported that the mass had been biopsied 3 years earlier and was found to be a seborrheic keratosis. The patient complained of a new-onset bloody discharge from the lesion in addition to the development of a parotid mass.

Physical examination revealed the presence of a 2 x 2cm, ulcerated, mobile, nontender scalp mass, a right parotid mass, and supraclavicular lymphadenopathy. A shave biopsy of the scalp lesion and fine-needle aspiration of the neck mass were performed. Histopathologic examination of the scalp specimen determined that it was an ulcerated, malignant tumor with features of both a benign and malignant neoplasm adjacent to each other (figure 1). The malignant component was consistent with a poorly differentiated adenocarcinoma (figures 2 and 3). Adjacent to the malignant cells were a few well-demarcated nodules of small, bland, polyhedral squamoid cells with focal duct formation (figures 1 and 4). Analysis of fineneedle aspiration material from the right cervical lymph node confirmed the presence of a malignant neoplasm. Computed tomography (CT) of the head detected a mass overlying the vertex of the skull without intracranial extension. CT of the neck demonstrated a 1-cm right cervical lymph node and a 1-cm intrap arotid mass.

The patient was treated with wide local excision of the scalp lesion, right neck dissection (levels 1 through 5), and a superficial right parotidectomy. He was administered adjuvant radiotherapy in light of the histologic evidence of perineural and perivascular involvement (figure 5).

Two years later, the patient returned to the clinic with a firm, immobile mass that involved the left parotid gland along with cervical adenopathy in left level 5. Histopathologic analysis of a fine-needle aspiration biopsy specimen revealed that it also represented an MEA.

Discussion

MEA is a subtype of adenocarcinoma that originates in the eccrine glands. The diagnosis of MEA in this case was established by the presence of both a benign and malignant neoplasm in the same tumor--that is, there was a recognizable benign eccrine acrospiroma adjacent to the malignant tumor cells (figure 1). The malignant component of this tumor was characterized by solid, glandular, and papillary patterns and was histologically consistent with a poorly differentiated adenocarcinoma (figures 2 and 3).

On the basis of pathologic findings, the differential diagnoses include eccrine adenocarcinoma not otherwise specified (NOS), porocarcinoma, apocrine carcinoma, malignant chondroid syringoma, and eccrine spiradenoma. The tumor in our patient would have been classified as an eccrine adenocarcinoma NOS if the benign eccrine acrospiroma component had not been present. The diagnosis of eccrine adenocarcinoma NOS also requires the clinical exclusion of a cutaneous metastasis from an internal malignancy, such as a primary tumor in the gastrointestinal tract or lung. (6, 7)

We considered the possibility of a porocarcinoma, the malignant counterpart of an eccrine poroma. Benign eccrine poromas and acrospiromas are related tumors with similar cytologic features. Both contain small squamoid cells that resemble those of seborrheic keratosis. A poroma is a superficial tumor confined to the epidermis and upper dermis. An eccrine acrospiroma is a deep dermal or subcutaneous nodular neoplasm that is sometimes connected to the epidermis. (6,7) In retrospect, the part of our patient's biopsy specimen that was diagnosed as seborrheic keratosis was either a poroma or the superficial portion of a benign acrospiroma that was connected to the epidermis. One of the nodules of the benign component in this case was located at the base of the biopsy specimen beneath the malignant component (adenocarcinoma). Therefore, a diagnosis of MEA was favored over a diagnosis of porocarcinoma. Moreover, the malignant transformation in most porocarcinomas resembles that of a squamous cell carcinoma rather th an an adenocarcinoma, as was seen in our patient. (8)

Apocrine carcinoma usually arises in the "apocrine areas"--that is, in the axilla. The cells in this neoplasm have ample granular eosinophilic cytoplasm and the characteristic decapitation secretion. (9) These features were not seen in our patient's tumor. Malignant chondroid syringoma was excluded in light of the absence of myxoid and chondroid stroma, which are hallmarks of chondroid syringoma. (10) Similarly, malignant eccrine spiradenoma was excluded on the basis of the absence of benign eccrine spiradenoma cells. Eccrine spiradenoma is made up of small, primitive-looking basaloid cells that are different from the squamoid cells seen in eccrine acrospiroma. (11)

Reports in the literature consistently emphasize the slow growth rate of both malignant and benign eccrine acrospiromas. Although MEAs usually arise de novo, malignant transformation in long-standing lesions can occur. Hunt et al reported a case of MEA that had been present for 40 years, which strongly suggests a malignant transformation of a pre-existing benign tumor. (5) Our patient's tumor had been present for 20 years, and the fact that his biopsy specimen yielded histologic evidence of both benign and malignant components again suggested a malignant transformation.

Benign eccrine acrospiromas range in size from 0.5 to 12 cm, while malignant forms tend to be of moderate size; the largest reported malignant tumor was 4 cm. (1,2,5,12) Some MEAs have been reported to produce a serous discharge, while others have been described as ulcerated lesions. (1,3,5)

The clinical similarity of malignant and benign eccrine acrospiromas to other cutaneous lesions (e.g., hemangiomas, squamous cell carcinomas, basal cell carcinomas, and malignant melanomas) necessitates a histologic diagnosis. A diagnosis of MEA can be arbitrary because there are no strict diagnostic criteria set forth in the literature. Features that distinguish malignant from benign eccrine acrospiromas include pleomorphism, atypical mitotic figures, infiltrative patterns, and perineural and angiolymphatic invasion. (1,4,5,13) When present, benign components with ducts and bland polyhedral squamoid cells adjacent to malignant tissue can facilitate and ensure the diagnosis, as happened in the case presented here (figure 1). The presence of benign tissue provides a valuable point of reference for diagnosing poorly differentiated adjacent malignant tissue. However, the detection of both benign and malignant tissue in the same tumor often necessitates multiple biopsies to preclude a sampling error. In our case , the diagnosis was unequivocal.

Although histology is used to distinguish benign from malignant eccrine spiromas, there have been reports of tumors with bland tissue architecture that recurred locally or metastasized. (2,3,14) Similarly, there are cases of eccrine acrospiromas with atypical nuclear changes and cellular pleomorphism that are clinically benign. (2) Close follow-up of all eccrine acrospiromas is necessary because histology is not always a reliable indicator of biologic behavior.

Malignant eccrine acrospiromas tend to progress in a predictable pattern from the tumor site to regional lymph nodes and ultimately to systemic metastases. (13) Treatment consists of wide local excision. Some authors advocate Mohs' surgery initially to debulk the clinically apparent tumor and to determine the extent of its subclinical spread. (4,12) Local tumor removal is important for lesions of uncertain behavior and histology. The risk of local recurrence has been reported to approach 50%, and metastatic rates are closer to 60%. (15) Although the metastatic rate is high, there is no general recommendation in the literature for elective neck dissection without clinically apparent adenopathy. (4)

There have been reports that acrospiromas are radio-resistant, but these reports did not include information regarding the specific technique, the volume radiated, or the cumulative dose administered. (13,14) Locoregional irradiation might be beneficial in malignant tumors at risk for local recurrence. (13) Several factors are associated with an increased incidence of local recurrence, including dermal lymphatic invasion, perineural invasion, deep structure infiltration, positive resection margins, highly anaplastic morphology, and extracapsular lymph node extension. (13) Various anecdotal reports indicate that these tumors are resistant to chemotherapy. (16)

References

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From the Department of Surgery, Baylor University Medical Center, Dallas (Dr. Holden), and the Department of Dermatology (Dr. Colome-Grimmer), the Department of Surgery (Dr. Savage), and the Department of Otolaryngology (Dr. Stierman and Dr. Pou), the University of Texas Medical Branch, Galveston.

Reprint requests: Anna M. Pou, MD, Department of Otolaryngology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555. Phone: (409) 772-9932; fax: (409) 7721715; e-mail: anpou@utmb.edu

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