Hidradenoma is an uncommon benign neoplasm of sweat gland origin that usually presents as a solitary, well-circumscribed, skin-colored or erythematous nodule [4]. Its malignant counterpart, hidradenocarcinoma, arises de-novo or from untreated hidradenoma and can behave aggressively with metastasis and recurrence [5]. These adnexal tumors present diagnostic challenges because of their overlapping features with one another and other cutaneous neoplasms and their frequent deviation from classic histopathologic morphologies [3]. Their histopathologic variability is underscored by the multiple terms used to describe hidradenoma and hidradenocarcinoma [5]. Diagnostic uncertainty can lead to misclassification of disease with consequent clinical impact [1]. To provide a more robust clinical context that can assist with the diagnosis and understanding of these neoplasms, we describe demographic and clinical characteristics for 64 patients diagnosed with hidradenoma and hidradenocarcinoma.
We performed a natural-language query for medical records from Massachusetts General Hospital and Brigham and Women’s Hospital to identify all patients from January 2000 through April 2023 with biopsy-proven diagnoses of hidradenoma, hidradenocarcinoma, or malignant transformation from hidradenoma to hidradenocarcinoma. A total of 64 cases met the criteria for analysis with diagnoses of hidradenoma (n=39), hidradenocarcinoma (n=20), or malignant transformation from hidradenoma to hidradenocarcinoma (n=5) (Table 1 and Table 2). Of these patients, 35 (54.7%) were males and 29 (45.3%) were females; 54 (84.4%) were white/Caucasian. Tumors were diagnosed on every major body surface, with the face (n=10, 15.6%) and scalp (n=7, 10.9%) being the most common sites. 44 (68.8%) patients underwent wide local excision of their tumor, 5 (7.8%) received radiotherapy, and 1 (1.6%) patient received chemotherapy. Malignant transformation from hidradenoma to hidradenocarcinoma resulted from untreated hidradenoma (n=2) and inadequate benign tumor excision (n=3). Of the 25 patients diagnosed with hidradenocarcinoma, four (16%) had distant metastases of their tumors, and one had mortality associated with their tumor.
Several findings in our study contribute to the existing knowledge and understanding of hidradenoma and its malignant counterpart. Our analysis demonstrated a similar distribution between the sexes for hidradenoma (18 females, 21 males), though in the 25 malignant cases, males were overrepresented (n=17, 68%) compared to females (n=8, 32%). The low utilization of chemotherapy and radiotherapy suggests these modalities are typically reserved for potentially more aggressive initial presentations. Our study also highlights the rarity of disease-associated morbidity, recurrence, and distant metastasis, consistent with other findings of hidradenocarcinoma in the literature [2]. Nevertheless, the identification of distant metastasis in a subset of hidradenocarcinoma cases emphasizes the importance of vigilant monitoring and early intervention in high-risk patients. Additionally, the association of malignant transformation with untreated hidradenoma and inadequate benign tumor excision reiterates the critical role of timely and appropriate interventions.
Our findings are limited by the retrospective nature of the analysis over a single multicenter setting. The observed clinical patterns, treatment approaches, and outcomes may aid clinicians in the diagnosis and management of these rare sweat gland neoplasms. Further research is warranted to validate our findings and enhance the current understanding of the clinical spectrum of hidradenoma and hidradenocarcinoma, especially regarding factors that potentially influence malignancy risk such as tumor site and patient sex.
Table 1. Clinical and Demographic Findings of Individuals with Hidradenoma and Hidradenocarcinoma (n=64)
|
|
Hidradenoma
|
Hidradenocarcinoma
|
Malignant Transformation
|
Total
|
|
|
n
|
%
|
n
|
%
|
n
|
%
|
n
|
%
|
|
Total
|
39
|
|
20
|
|
5
|
|
64
|
|
|
Sex
|
|
|
|
|
|
|
|
|
|
Female
|
21
|
(54)
|
7
|
(35)
|
1
|
(20)
|
29
|
(45)
|
|
Male
|
18
|
(46)
|
13
|
(65)
|
4
|
(80)
|
35
|
(55)
|
|
Race/Ethinicity
|
|
|
|
|
|
|
|
|
|
American Indian/Alaska Native
|
0
|
(0)
|
0
|
0
|
0
|
0
|
0
|
0
|
|
Asian
|
1
|
(3)
|
0
|
0
|
0
|
0
|
1
|
(2)
|
|
Black/African American
|
2
|
(5)
|
2
|
(10)
|
0
|
0
|
4
|
(6)
|
|
Hispanic/Latino
|
5
|
(13)
|
0
|
0
|
0
|
0
|
5
|
(8)
|
|
Native Hawaiian/Pacific Islander
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
|
White/Caucasian
|
31
|
(80)
|
18
|
(90)
|
5
|
(100)
|
54
|
(84)
|
|
Lesion Location
|
|
|
|
|
|
|
|
|
|
Scalp
|
7
|
(18)
|
0
|
0
|
0
|
0
|
7
|
(11)
|
|
Face
|
7
|
(18)
|
3
|
(15)
|
0
|
0
|
10
|
(16)
|
|
Neck
|
1
|
(3)
|
1
|
(5)
|
0
|
0
|
2
|
(3)
|
|
Chest
|
3
|
(8)
|
1
|
(5)
|
0
|
0
|
4
|
(6)
|
|
Back
|
2
|
(5)
|
1
|
(5)
|
1
|
(20)
|
4
|
(6)
|
|
Abdomen
|
1
|
(3)
|
0
|
0
|
0
|
0
|
1
|
(2)
|
|
Buttock
|
2
|
(5)
|
1
|
(5)
|
0
|
0
|
3
|
(5)
|
|
Proximal Upper Extremity
|
3
|
(8)
|
0
|
0
|
1
|
(20)
|
4
|
(6)
|
|
Proximal Lower Extremity
|
1
|
(3)
|
1
|
(5)
|
1
|
(20)
|
3
|
(5)
|
|
Distal Upper Extremity
|
3
|
(8)
|
2
|
(10)
|
1
|
(20)
|
6
|
(9)
|
|
Distal Lower Extremity
|
4
|
(10)
|
1
|
(5)
|
0
|
0
|
5
|
(8)
|
|
Hands
|
2
|
(5)
|
3
|
(15)
|
0
|
0
|
5
|
(8)
|
|
Feet
|
1
|
(3)
|
4
|
(20)
|
0
|
0
|
5
|
(8)
|
|
Other
|
2
|
(5)
|
2
|
(10)
|
1
|
(20)
|
5
|
(8)
|
Table 2. Disease Management and Outcomes of Individuals with Hidradenoma and Hidradenocarcinoma (n=64)
|
|
Hidradenoma
|
Hidradenocarcinoma
|
Malignant Transformation
|
Total
|
|
|
n
|
%
|
n
|
%
|
n
|
%
|
n
|
%
|
|
Total
|
39
|
|
20
|
|
5
|
|
64
|
|
|
Wide Local Excision Performed
|
|
|
|
|
|
|
|
|
|
Yes
|
23
|
(59)
|
16
|
(80)
|
5
|
(100)
|
44
|
(69)
|
|
No
|
12
|
(31)
|
4
|
(20)
|
0
|
0
|
16
|
(25)
|
|
Unknown
|
4
|
(10)
|
0
|
0
|
0
|
0
|
4
|
(6)
|
|
Further Surgery (MOHS, etc)
|
|
|
|
|
|
|
|
|
|
Yes
|
3
|
(8)
|
8
|
(40)
|
2
|
(40)
|
13
|
(20)
|
|
No
|
29
|
(74)
|
8
|
(40)
|
3
|
(60)
|
40
|
(63)
|
|
Unknown
|
7
|
(18)
|
4
|
(20)
|
0
|
0
|
11
|
(17)
|
|
Received Radiotherapy
|
|
|
|
|
|
|
|
|
|
Yes
|
1
|
(3)
|
4
|
(20)
|
0
|
0
|
5
|
(8)
|
|
No
|
30
|
(77)
|
12
|
(60)
|
5
|
(100)
|
47
|
(73)
|
|
Unknown
|
8
|
(21)
|
4
|
(20)
|
0
|
0
|
12
|
(19)
|
|
Received Chemotherapy
|
|
|
|
|
|
|
|
|
|
Yes
|
0
|
0
|
1
|
(5)
|
0
|
0
|
1
|
(2)
|
|
No
|
29
|
(74)
|
14
|
(70)
|
3
|
(60)
|
46
|
(72)
|
|
Unknown
|
10
|
(26)
|
5
|
(25)
|
2
|
(40)
|
17
|
(27)
|
|
Disease Recurrence
|
|
|
|
|
|
|
|
|
|
Yes
|
1
|
(3)
|
0
|
0
|
0
|
0
|
1
|
(2)
|
|
No
|
30
|
(77)
|
15
|
(75)
|
5
|
(100)
|
50
|
(78)
|
|
Unknown
|
8
|
(21)
|
5
|
(25)
|
0
|
0
|
13
|
(20)
|
|
Distant Metastasis
|
|
|
|
|
|
|
|
|
|
Yes
|
0
|
0
|
2*
|
(10)
|
2**
|
(40)
|
4
|
(6)
|
|
No
|
32
|
(82)
|
12
|
(60)
|
3
|
(60)
|
47
|
(73)
|
|
Unknown
|
7
|
(18)
|
6
|
(30)
|
0
|
0
|
13
|
(20)
|
|
Morbidity Associated with Disease
|
|
|
|
|
|
|
|
|
|
Yes
|
0
|
0
|
1
|
(5)
|
0
|
0
|
1
|
(2)
|
|
No
|
8
|
(21)
|
6
|
(30)
|
1
|
(20)
|
15
|
(23)
|
*Hidradenocarcinoma metastases to: femur, humerus, chest wall, small bowel, and soft tissue in one patient and right inguinal in the second patient
**Malignant transformation of hidradenoma to hidradenocarcinoma metastases to: left inguinal lymph node in one patient and right axilla in the second patient