The patient presented to the outpatient department with a solitary, asymptomatic 2 × 2.5 cm nodule on the medial humeral region. The lesion had appeared some years ago but gradually increased in size during the last months, causing a palpable skin lump with red coloration.
Ultrasound examination of the lesion was performed with a linear high frequency (13MHz) transducer and using enough quantity of ultrasonic gel in order to avoid contact of the transducer with the skin. As a result, the skin layers were adequately imaged. The palpable lesion was located in the dermis and extending to the subcutaneous tissue, appearing on greyscale technique as a mass with mixed echogenicity including both solid and cystic parts. The mass measured 2.2x1.5 cm and had no microcalcifications. (Fig. 1) On colour, power Doppler and eFlow technique, the mass showed marked vascularity in both the periphery of the mass and within its solid parts. (Fig. 2) The lesion was surgically removed and histology established the diagnosis of a hidradenoma. (Fig. 3)
Clear cell or nodular hidradenomas represent rare benign tumours of the skin originating from the eccrine sweat glands. They can be found in any age but show a slight predilection for the fourth decade and female patients. Hidradenomas are usually located in the head, face, extremities and trunk. [1, 2, 3] There is only a limited number of published cases located in the breast. This type of tumour is typically located in the skin layer of dermis or the subcutaneous adipose tissue and is covered by a normal epidermis. Skin symptoms like thickening, ulceration or serous discharge may occur. [1]
Due to its overall rarity and the fact that most lesions are surgically removed and diagnosed based on histology, imaging findings are rarely reported in the literature. [3] Ultrasound is the primary imaging modality for evaluation of any palpable soft tissue lump, as it is the case in hidradenomas. Mammography has been used to evaluate breast lesions. Hidradenomas appear on ultrasound as single, well-demarcated, rounded nodules measuring 0.5 cm to 3 cm. In terms of echogenicity, hidradenomas usually present as cystic lesions with mural solid nodules or alternatively as solid tumours with areas of hypoechogenicity. Colour Doppler technique is useful and demonstrates hypervascularity within solid lesions or the solid mural nodules of a complex mass. Hidradenomas echogenicity may be further complicated by calcifications or hyperechoic areas representing haemorrhagic changes. [1, 2, 4] All these ultrasonographic findings have been found to correlate with histological findings. [3]
On MRI, hidradenomas are identified as subcutaneous complex cystic and solid masses showing low to intermediate signal intensity on T1-weighted images and intermediate to high signal intensity on T2-weighted images. As it happens with ultrasound, haemorrhagic changes of the cystic part of the lesions may complicate their appearance by altering signal intensity. Following intravenous administration of contrast material, the solid parts of the tumour show enhancement. [1, 2] Cystic parts of hidradenomas may sometimes demonstrate fluid levels. [2]
Hidradenomas only rarely show malignant transformation. [1, 5] The differential diagnosis between hidradenomas and malignant hidradenocarcinoma relies on the aggressive local invasion and the distant metastases of the latter. Treatment of hidradenomas include complete surgical excision with clear margins to prevent recurrence due to tumour remnants by an inadequate excision. [1]
Although rarely investigated with imaging, hidradenomas should be included in the differential diagnosis of a subcutaneous complex and hypervascular lesion with solid and cystic parts.
Hidradenoma
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1. The patient is a 64-year-old male with a solitary palpable skin nodule located on the medial side of the humerus, measuring approximately 2 × 2.5 cm.
2. Ultrasonographic images show a relatively well-defined nodule with both solid and cystic components; areas of heterogeneous echoes possibly indicate hemorrhage or cystic degeneration.
3. Color Doppler reveals abundant blood flow signals within the nodule, suggesting a hypervascular solid component.
4. Histopathological images demonstrate cellular proliferation derived from sweat glands, overall consistent with the morphological features of a benign tumor.
Based on the above imaging findings and pathological suggestions, the following possible diagnoses should be considered:
Taking into consideration the patient's age, clinical progression, and the ultrasound and pathological findings, the most likely diagnosis is:
Nodular (Clear Cell) Sweat Gland Adenoma (Hidradenoma).
This lesion is a benign tumor of sweat gland origin with a low incidence of malignant transformation. Given the current localized lesion, absence of invasive or metastatic features, it aligns with a benign profile.
1. Treatment Strategy:
(1) Surgical Treatment: Complete surgical excision is recommended following thorough evaluation, ensuring clear margins to reduce the risk of recurrence.
(2) Pathological Follow-Up: Postoperative pathological examination is essential to rule out rare malignant components. If any malignant features are detected, further comprehensive treatment may be required.
(3) Prognosis: Generally favorable. If margins are clear, the recurrence rate is low.
2. Rehabilitation/Exercise Prescription:
(1) Early Postoperative Period (1–2 Weeks): During wound healing, protect the local site and avoid excessive pulling. Perform gentle range-of-motion exercises (e.g., light flexion and extension) to improve circulation.
(2) Recovery Period (2–6 Weeks): Gradually increase the range and intensity of limb activities, focusing on active shoulder and elbow joint exercises to prevent adhesion. Exercise frequency can be 3–5 times per week, 20–30 minutes each time, at an intensity that does not cause significant pain.
(3) Strengthening Phase (After 6 Weeks): Once the incision has healed well and there are no signs of infection or other complications, consider adding resistance training for the upper limb (e.g., using resistance bands, light weights), about 3 times per week, each session 20–40 minutes, in combination with moderate aerobic exercises (such as brisk walking) to enhance overall fitness and muscle strength.
(4) Precautions: If the patient experiences increased incisional pain, skin redness, or other discomfort, seek medical advice promptly. Any new symptoms should be evaluated by a healthcare professional.
This report is a reference medical analysis based on existing data and does not replace an in-person consultation or professional medical advice. A specific diagnosis and treatment plan must be determined in conjunction with the patient’s condition and the professional assessment of medical personnel.
Hidradenoma
