Nodular Hidradenoma
Nodular hidradenoma (also called hidradenoma, clear cell hidradenoma or eccrine acrospiroma) is a benign cutaneous adnexal tumor that arises from epithelial germ cells differentiating toward the duct or secretory portion of the sweat glands (eccrine or apocrine).
It typically forms solid nodules combined with fluid-filled cystic areas, lying deep in the dermis and subcutis.
The CRTC1-MAML2 Gene Rearrangement
- Translocation t(11;19)(q21;p13): Fusion of the CRTC1 gene (CREB regulated transcription coactivator 1) with MAML2 (mastermind-like 2) produces a CRTC1-MAML2 hybrid protein. This protein keeps the CREB and Notch signaling pathways switched on, driving the epithelial cells to proliferate continuously while they retain sweat gland differentiation.
- An unusual genetic link: Because of this shared CRTC1-MAML2 fusion, hidradenoma of the skin is molecularly related to mucoepidermoid carcinoma of the salivary glands.
Malignant Change (Hidradenocarcinoma)
Although most nodular hidradenomas are benign, a small proportion undergo secondary malignant transformation or arise from the outset as hidradenocarcinoma.
- Mutations in the TP53 tumor suppressor gene or PIK3CA, or increased EGFR signaling, cause tumor cells to divide uncontrollably and raise the risk of deep invasion, perineural spread and regional lymph node metastasis (20–50%).
Nodular hidradenoma is multicystic and has a rich blood supply. At Haute-Derma, definitive treatment means removing the entire cyst wall and the tumor base deep in the dermis:
- Thorough diagnostic assessment: Dermoscopy and 20–50 MHz high-frequency skin ultrasound to distinguish solid from cystic components and measure the depth of the tumor.
- Cosmetic complete excisional surgery: The lesion is removed in one piece with a microscopically clear safety margin. Mohs surgery is added when the tumor sits in a cosmetically sensitive area (face, eyelids) or when immunohistochemistry (IHC) raises suspicion of malignancy.
Histopathology, Immunohistochemistry (IHC) and Imaging Criteria
Characteristic Features Under the Microscope
Nodular hidradenoma appears as a well-circumscribed dermal tumor without a complete fibrous capsule, made up of a biphasic cell population:
- Clear cells: Pale, clear cytoplasm packed with glycogen and a small, round, central nucleus.
- Polyhedral (poroid) cells: Dense, eosinophilic (pink) cytoplasm with uniformly dark nuclei.
- Cystic spaces: Formed by degeneration and necrosis of cells in the center of the tumor; they contain cloudy proteinaceous fluid or acellular necrotic debris.
- Ductal lumens: Scattered small ducts lined by a single layer of columnar or flattened cells.
High-Frequency Ultrasound and Dermoscopy Criteria
- High-frequency skin ultrasound (20–50 MHz):
- Mixed solid-cystic mass: The fluid-filled cystic part is anechoic, while the hypoechoic solid part represents the tumor lobules.
- Margins: Well defined, with posterior acoustic enhancement.
- Color Doppler: Increased vascular signal concentrated in the cyst walls and the solid parts of the mass.
- Dermoscopy:
- Background color: A structureless, homogeneous pinkish-red or pinkish-gray background.
- Vessels: Arborizing-like or polymorphous vessels in the superficial layer.
- Hazy areas: Round white-yellow structures that correspond to nests of clear cells or small cystic spaces.
Clinical Features
- Typical lesion: A single papule or nodule under the skin, 0.5–3 cm, firm or tense and cyst-like, skin-colored, brick-red or faintly bluish-purple.
- Associated symptoms: Usually painless, but it can be mildly tender or ooze blood or mucus if the cyst ruptures or the overlying skin breaks.
- Common sites: Head, face, neck, trunk and limbs.
Immunohistochemical (IHC) Markers and Special Stains
| Marker / Stain | Diagnostic Significance | Finding in Nodular Hidradenoma |
|---|---|---|
| PAS (periodic acid-Schiff) | Stains glycogen in clear cells | Strongly positive (+) in the cytoplasm |
| PAS + diastase | Diastase digests glycogen | Negative (confirms the material is glycogen) |
| CK7 / CK19 | Sweat duct epithelial markers | Diffusely positive (++) |
| CEA / EMA | Epithelial membrane antigens lining the ducts | Clearly positive along the duct lumens |
| p63 / calponin | Myoepithelial / basaloid cells | Positive at the periphery of the tumor |
| Ki-67 index | Proliferation index, used to assess malignancy | Benign: <5%. Malignant (hidradenocarcinoma): >20–40% |
Treatment at Haute-Derma
Our approach to nodular hidradenoma at Haute-Derma pursues two goals together: removing the entire tumor base to minimize the risk of recurrence, and achieving the best possible cosmetic result:
Deep Assessment and Multimodal Imaging
- 50 MHz ultrasound to map depth: Shows whether the base of the tumor extends through the deep fascia and estimates the volume of the cystic part, so the incision can be planned appropriately.
- Biopsy with IHC screening: A panel of CK7, PAS, CEA and Ki-67 index is used to rule out malignant change to hidradenocarcinoma.
Individualized Surgery
Cosmetic Full-Thickness Surgical Excision:
- Used for benign nodular hidradenomas on the trunk or limbs.
- A close-fitting elliptical incision with a 2–3 mm safety margin. The solid and cystic parts are removed together, down to the subcutis, without rupturing the cyst wall, so that tumor cells are not spilled into the surrounding tissue.
Mohs Micrographic Surgery:
- Used for tumors in cosmetically important areas (face, eyelids, nose, ears), for recurrent tumors and for lesions with a high Ki-67 proliferation index.
- The surgeon removes the tumor and examines 100% of the side and deep margins on frozen sections during the procedure, stopping only once clear margins are confirmed.
Wound Healing and Cosmetic Repair
- Exosome and purified PDRN irrigation: Right after the tumor is removed, the wound bed is covered with a stem cell-derived exosome solution combined with PDRN to encourage healthy new capillaries and help the defect fill in quickly.
- Three-layer subcuticular closure: The wound edges are brought together with ultra-fine 7-0 cosmetic sutures to take tension off the skin surface.
- Scar-prevention treatments: 595 nm Vbeam laser after 7–14 days to fade the red blood vessels around the incision, combined with 633 nm red LED light to help the scar flatten and smooth out faster.
