Apocrine Carcinoma of the Skin, from the CureRays guide library.

Primary cutaneous apocrine carcinoma is a rare sweat-gland skin cancer of the underarm and groin; surgery is the main treatment, with radiation for high-risk or node-positive disease.

What it is.

The skin has two kinds of sweat glands; the apocrine glands are concentrated in the armpit, groin, and around the nipple and genitals. Primary cutaneous apocrine carcinoma is a very rare cancer that grows from these glands, usually appearing as a slow-growing lump or nodule in those areas in middle-aged and older adults. Although it often grows slowly, it has a meaningful tendency to reach nearby lymph nodes and can recur, so it is taken seriously. Because some apocrine carcinomas carry hormone receptors (similar to certain breast cancers), hormone-blocking therapy is occasionally an option for advanced disease. As with other sweat-gland cancers, doctors first confirm the skin is the true origin rather than spread from the breast.

How radiation treats it.

Radiation focuses high-energy beams on the tumor area to break the DNA of cancer cells so they can no longer divide, clearing microscopic disease that surgery may leave behind. For apocrine carcinoma, radiation is mainly used after surgery for high-risk or node-positive tumors, or to treat involved lymph nodes, improving local and regional control. The beam is shaped to the surgical bed and any at-risk nodes while sparing surrounding skin and tissue. Treatment is painless and delivered as a series of short daily sessions, with a temporary skin reaction being the usual side effect.

The ways we can treat it.

Adjuvant external-beam radiation. Targets the tumor bed and, when needed, the draining nodes after surgery to lower the chance of local and regional recurrence in high-risk tumors.

Nodal radiation. When lymph nodes are involved or there is concern for residual disease, the nodal area is irradiated as part of regional control.

Anti-hormone therapy (selective). For hormone-receptor-positive tumors that have spread, androgen- or estrogen-blocking pills can slow the cancer — a strategy borrowed from breast-cancer care.

Questions we hear often.

Where does this cancer usually appear? In areas rich in apocrine sweat glands — most often the armpit and groin, and sometimes around the nipple or genitals — as a slow-growing lump.

Why are my lymph nodes being checked? Apocrine carcinoma reaches the nearby lymph nodes more often than most sweat-gland cancers, so checking and, if needed, treating them is an important part of care.

I heard it can be treated like breast cancer — is that true? Sometimes. A portion of apocrine carcinomas carry hormone receptors, so for advanced disease, hormone-blocking pills used in breast cancer can be an option after the tumor is tested.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.