Primary Apocrine Adenocarcinoma of the Axilla

Primary apocrine adenocarcinoma (AA) is a rare cutaneous malignancy, with most of the available information about this disease consolidated from anecdotal evidence of single case reports and small case series with fewer than 30 patients.^1-11 Although certain histologic and immunohistochemical features have been suggested to be useful in the diagnosis of AA, there is no clear consensus on the required pathologic criteria.^{1,5,6,9,10,12,13} Additionally, the clinical presentation of AA is highly variable, which further adds to the challenge of making an accurate diagnosis.^{1-3,5,9,10,13}

Apocrine adenocarcinoma usually arises in areas of high apocrine gland density such as the axillae or anogenital region.^2,4,6 It also has been reported in areas such as the scalp, ear canal, eyelids, chest, nipples, arms, wrists, and fingers.^4,8,10,14-16 Apocrine adenocarcinoma in unusual locations such as the eyelid and ear canal is thought to arise from modified apocrine glands such as the Moll glands of the eyelid and the ceruminous glands of the ear canal.^9,10 The presence of ectopic apocrine glands may lead to AA in atypical sites such as the wrists and fingers.^5,16 The areola is an apocrine-dense area; therefore, AA may present on the nipples or within supernumerary nipples anywhere along the milk lines.⁴

Apocrine adenocarcinoma clinically presents as an asymptomatic to slightly painful, slowly growing, and erythematous to violaceous nodule or tumor.^4,6,9 However, in a minority of cases the initial presentation consists of a cystic or ulcerated mass with overlying granulation tissue and purulent discharge.^6,9,11 A wide time frame from the onset of symptoms to diagnosis has been reported, ranging from weeks to decades.^4,6-8 The conventional treatment of AA is wide local excision.^2,4,6,9 Although AA often presents with local lymph node metastasis at the time of diagnosis, there is no consensus on the use of sentinel lymph node biopsy (SLNB), nodal dissection, or adjuvant chemoradiation therapy.^1,3,8,9

We report the case of a 49-year-old man with primary AA of the left axilla; the clinical and histologic features of AA as well as the appropriate diagnostic and treatment modalities also are provided.

Case Report

A 49-year-old man with a slowly growing tender mass of the left axilla of 1 year’s duration was referred to our dermatology clinic for evaluation. A review of systems revealed loss of appetite, fatigue, and a 4-month history of unintentional weight loss (15–20 lb). The patient had a history of hepatitis C virus, intravenous drug use, alcohol abuse, and cigarette smoking (1 pack daily) for many years. Additionally, the patient reported a paternal family history of numerous visceral malignancies. Examination of the left axilla revealed a 1.5×5-cm ulcerated tumor that produced serosanguineous discharge and was tender to palpation (Figure 1). Two 1-cm, firm, freely mobile subcutaneous nodules with no overlying skin changes were palpable at the medial border of the ulcerated nodule. There was no additional cervical or axillary lymphadenopathy, and a breast examination was normal.

^{Figure 1. A 1.5×5-cm ulcerated tumor on the left axilla with firm palpable lymph nodes on the medial border.}

The differential diagnosis included primary squamous cell carcinoma or adnexal neoplasm, primary breast carcinoma, lymphoma, scrofuloderma, atypical mycobacterial infection, and cutaneous metastasis from an internal malignancy. Two 4-mm punch biopsies were performed and sent for routine histopathology and bacterial, fungal, and mycobacterial tissue cultures. To exclude a primary visceral malignancy or metastasis, computed tomography of the chest, abdomen, and pelvis; positron emission tomography (PET) from the base of the skull to the thighs; colonoscopy; magnetic resonance imaging of the brain; esophagogastroduodenoscopy; and mammography were conducted. Prominent left axillary lymphadenopathy was noted on computed tomography. Additionally, PET identified extranodal spread in the left axilla, left lateral chest wall, and the left sternocleidomastoid region. Furthermore, a 1-cm hypermetabolic nodule involving the right rectus abdominus muscle was noted on the PET scan. Based on their appearance, the nodules most likely represented metastasis from a primary skin malignancy. The rest of the studies were unremarkable. Serum tumor markers including prostate-specific antigen, cancer antigen 19-9, and carcinoembryonic antigen were within reference range. Immunostaining for estrogen receptor, progesterone receptor, and ERBB2 (formerly HER2/neu) was negative. The only abnormalities noted on serum chemistries were slight elevations in aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and the a-fetoprotein tumor marker, which was attributed to chronic hepatitis C infection. Bacterial, fungal, and mycobacterial tissue cultures also were negative. These results ruled out infection and suggested against a primary visceral malignancy with cutaneous metastasis.

Histopathology revealed a moderately differentiated adenocarcinoma adjacent to healthy-appearing apocrine glands (Figure 2A). The normal glands were composed of cuboidal cells with abundant eosinophilic cytoplasm and prominent nuclei. The cells were arranged in a single layer in a glandular formation with prominent decapitation secretion. Adjacent to the normal apocrine glandular tissue was a focus of malignant epithelioid cells that extended to the lateral and inferior margins. The neoplastic cells were cuboidal to angulated in appearance with prominent nuclei and seemed to form ill-defined tubular or glandular structures that partially resembled apocrine glands (Figure 2B). Decapitation secretion is a feature of apocrine differentiation. Examination of additional tissue sections of the tumor did not reveal remarkable decapitation secretion in contrast to the adjacent healthy apocrine glands. Rather, a solid sheet arrangement was primarily noted in several sections (Figure 2B). Neither frequent mitoses nor prominent cellular atypia were seen, and there was no evidence of lymphatic, perineural, or vascular invasion.