Teaching Case

An 82-year-old woman with a history of luminal A-type invasive lobular carcinoma of the right breast presents with a palpable lump on the posterior third of the upper inner quadrant of the right breast, near the chest wall, close to the surgical scar. The primary tumour had been treated with conservative surgery and adjuvant chemoradiotherapy seven years prior, and the patient was currently under hormonotherapy. A punch biopsy was performed, and the initial result was suggestive of recurrent disease.

Because of the high degree of clinical suspicion, an MRI was performed as the initial imaging study.

In the upper-inner quadrant of the posterior third of the right breast, in the cutaneous plane, there is a mass-like lesion (blue arrows) with solid component, circumscribed margins, hypointensity on T2WI (Figures 1, 2 and 3), intermediate signal on T1WI (Figure 4), with late and persistent enhancement, and without significant restriction diffusion (Figures 5, 6, 7 and 8). No evidence of intralesional fat or cystic components is present. No evidence of adenopathy on the axilla. No other foci of abnormal enhancement or signal were noted.

Nodular hidradenomas, also called solid cystic hidradenomas, and eccrine acrospiromas, is a rare, generally benign, cutaneous adnexal-type neoplasm originating from sweat glands, of eccrine or apocrine gland differentiation. These lesions arise from epithelial cells differentiating towards adnexal structures, including hair follicles, sebaceous glands, apocrine sweat glands, and eccrine sweat glands [1]. Nodular hidradenomas can occur anywhere in the body, more commonly found in the trunk, lower limbs and head, and few published cases describe hidradenomas in the breast [2].

Nodular hidradenomas can present as focal tenderness, skin discolouration, ulceration or cutaneous discharge [3], often found in the fourth to eighth decades, more commonly in women. On clinical observation, the overlying skin can be red, blue, thickened, papillated, or ulcerated [4]. Nodular hidradenomas usually present as a small, slow-growing, single, solid, intradermal nodule, covered with normal skin. They can, however, present as nodular, cystic, or solid components. A benign lesion can grow to be very large and may often recur after excision [5].

On pathology, hidradenomas present as nodules of epithelial cells within the upper or mid dermis, with no connection to the epidermis [9].

The malignant counterpart of nodular hidradenoma is hidradenocarcinoma, a highly aggressive tumour, that can be indistinguishable from nodular hidroadenoma at imaging. An enhancing component, which may manifest as a mural nodule, may be seen and does not necessarily denote malignancy [4].

Due to the initial suspicion of local cutaneous breast cancer recurrence, a breast MRI was required to evaluate the lesion’s extent and ensure that its removal would achieve oncologically safe margins. The appearance of hidradenomas on MRI is variable, often as a lobulated nodule, adherent to the skin, and demonstrating increased signal intensity on all pulse sequences [6,7] with fluid-fluid levels. This classical manifestation could prompt the choice of excisional biopsy upfront. However, the appearance in our case—of a nodular, enhancing mass, without fluid component—is not commonly found.

As shown in this case, both fine-needle aspiration and core biopsy may not be able to establish a reliable histopathologic diagnosis of nodulocystic hidradenoma. A fine-needle aspiration can fail to sample the solid component. Regarding core biopsy, the high cellularity and cellular changes—nuclear groves, membrane irregularities, and macronuclei—in addition to the rarity of nodular hidradenoma, could incorrectly suggest cutaneous breast cancer recurrence [8]. As such, surgical excision is often necessary to establish a definitive diagnosis.

In our case, due to the benign nature of the lesion, the course of management was imaging follow-up.

In conclusion, nodular hidradenoma of the breast is a rare but possible diagnosis for enhancing nodules in the skin. Excisional biopsy in this setting is often necessary to establish the definitive diagnosis, as it can both be curative and exclude malignancy.