Primary apocrine carcinoma of the axilla: a rare tumor

A 50‐year‐old male patient was referred for evaluation of a right axillary mass with five months of evolution, which recently presented with rapid growth and pain. On physical examination, an indurated, tender, subcutaneous mass was palpated. No other lesions were observed in the contralateral axilla or either breast.

Ultrasound (US) examination of the right axilla revealed a hypoechoic solid mass, well-demarcated, with irregular shape (Fig. 1). There was no axillary lymphadenopathy bilaterally and the examination of both breasts was unremarkable.

CT scan demonstrated a 3.9x3.1x3.2 cm solid axillary mass, with heterogeneous arterial enhancement and central necrosis on post-contrast acquisition. This lesion is limited to the subcutaneous tissue (Fig. 2). CT did not show relevant pulmonary, mediastinal, or upper abdominal findings.

Background

Primary apocrine carcinoma of the sweat gland is an extremely rare malignant neoplasm, with approximately 50 cases reported in the literature [1,2]. It occurs mostly in apocrine-dense regions such as the axilla and anogenital areas, although it has also been reported to occur in less typical locations such as the scalp, eyelid, ear, lip, chest, nipple, fingers, and toes [1-3]. Patients with apocrine adenocarcinoma are usually above 50 years of age [4].

Clinical Perspective

Most PAC are relatively indolent with a slow growth rate and are not clinically suspected before biopsy [1,3]. However, some are rapidly progressive and extremely aggressive showing development over weeks to months [3]. On physical exam these neoplasms present as erythematous/colourless, painless, solitary nodules, with 2-5 cm in size [1-4]. Most patients did not report any additional symptoms, but when present, they included pain, restriction of range of motion, ulceration, and purulent discharge [3]. Case reports support high local recurrence and regional lymph node metastasis [2]. Almost 50% had lymph node metastases at presentation [1,3]. Distant metastases have been reported in the lungs, liver, or bones [1,3].

Imaging Perspective

PET-CT, chest, abdominal, and pelvic CT can be performed to exclude the possibility of metastatic carcinoma from other malignant disorders, such as lymphomas or adenocarcinoma from the lung, GIT, etc, as well as to evaluate the local extension of the lesion and presence of distant metastasis [1,3,5]. Breast ultrasound, mammogram, or MRI are important modalities to exclude metastatic breast cancer [1-5]. In this case, US examination of both breasts was preferred, as well as US of both axilla for additional characterization of the lesion, to exclude contralateral lesions or local lymphadenopathy. To our knowledge, on imaging studies, Primary apocrine carcinoma presents as a well-demarcated, irregularly shaped, solid vascular lesion. These findings are not specific and biopsy with proper histopathology and immunohistochemistry examination are required to reach the diagnosis [1-5]. In our case, an ultrasound-guided core-needle biopsy was performed to obtain tissue samples for accurate diagnosis.

Outcome

Regional lymph node metastasis is considered an important prognostic factor [2]. The disease-free survival rate for 10 years in the absence of metastasis to the lymph nodes is reported to be 56%, this percentage drops to 9% if lymph node metastasis is involved [4]. The standard treatment consists of a wide local excision with clear margins and regional lymph node dissection for clinically positive nodes [1]. The literature has also explored the role of sentinel lymph node biopsy for clinically negative nodes, as well as adjuvant radiation therapy [1,3]. Our patient underwent surgical-wide local excision and adjuvant radiotherapy was not deemed necessary due to negative surgical margins and absence of regional lymphadenopathy.

Take Home Message / Teaching Points

Given its rarity and poor prognosis, this case wants to raise awareness for primary apocrine carcinoma as a possibility when differentiating axillary lesions.

Written informed patient consent for publication has been obtained.