Primary Cutaneous Apocrine Carcinoma

Dear Editor:

Primary cutaneous apocrine carcinoma (PCAC), a subtype of sweat gland carcinoma, is an extremely rare malignant neoplasm¹. Most of these neoplasms arise in regions of high apocrine gland density, particularly in the axilla, but lesions can also occur elsewhere on the skin. Frequently they are indolent and slowly developing, but some are rapidly progressive and aggressive². Wide, local excision with clear margins, with or without lymph node dissection is the standard treatment³.

A 44-year-old man visited our department because of a painless nodule on the right axilla, which had been present for more than 2 years. Physical examination revealed a flesh colored bean sized pedunculated nodule (Fig. 1). Bilateral breast examination was unremarkable and ultrasound examination showed no mass. The nodule was locally excised and histopathologic feature revealed a well-to-moderately differentiated adenocarcinoma located in the dermis containing ductal and glandular structures. The tumor cells contained abundant eosinophilic cytoplasm and showed decapitation. Luminal layers were composed of cuboidal or columnar secretory cells with atypia and a dilated lumen containing eosinophilic secreted materials (Fig. 2). The immunohistochemical staining study showed that the tumor cells were positive for GCDEF-15, cytokeratin (CK) 5/6 and CK7. Estrogen and progesterone receptor were not detected. No lymphatic emboli were found and there was no evidence of ectopic breast tissue. Based on the clinical and histopathological characteristics, the final diagnosis of PCAC was made. Apocrine carcinoma was first reported by Horn⁴ in 1944 and since then, only few cases have been reported in the literature. Cutaneous apocrine carcinoma has a slight male predominance and usually occurs in fifth decade of life. This tumor usually develops de novo, but can arise from other benign tumors such as apocrine adenoma or hyperplasia⁵. Adnexal carcinomas that develop de novo are difficult to diagnose clinically and require histopathologic evaluation. Histologically, these must be differentiated from cutaneous metastasis from breast³. The tumor is characterized by cells with abundant eosinophilic cytoplasm, eccrine basally located nuclei, and decapitation secretion in the luminal cells. GCDFP-15 has been known to stain apocrine rather than eccrine glands in axillary and anogenital skin². CK5/6 and CK7 are useful to differentiate a PCAC from a metastasis. CK5/6 positivity has been reported in 80% of PCAC whereas 6.66% of metastasis. Compare to such characteristics of PCAC described above, metastatic mammary adenocarcinomas are often positive for estrogen and progesterone receptors⁵.

Fig. 1. The 1.2×1.0 cm sized flesh to reddish colored pedunculated nodule on the right axilla.

Fig. 2. (A) Scanning view of the specimen. (B) Specimen showed a well-to-moderately differentiated adenocarcinoma located in the dermis containing ductal and glandular structures with apocrine features (H&E, ×100). (C) Dense cellular nests were composed of cells with abundant eosinophilic cytoplasm, vesicular nuclei and central large nucleoli. Some lumen showed decapitation (H&E, ×200).

Apocrine carcinomas are initially locally invasive, and systemic dissemination is often associated with regional lymph node metastasis³. Therefore the treatment of choice is wide local excision with clear margins. In our case, there was no metastasis including lymph nodes which was confirmed by ultrasonography and whole body positron emitting tomography/computed tomography and the lesion was removed by local excision with clear margins. In the 13 months since this operation, the patient has been well without local recurrence or metastasis.