Malignant tumor of the skin glands in dogs (Adenocarcinoma of the skin)
- Occurrence: rarer
- Location of disease: Skin/Fur
When to visit the vet?
Non-urgent see a veterinarian within 2–3 days
If the condition worsens / symptoms persist, consult a veterinarian.
Definition
Adenocarcinoma of the skin (cutaneous adenocarcinoma) is a malignant tumor that arises from the glandular structures of the skin. These malignant neoplasias can originate from various gland types, including sebaceous, sweat, or apocrine glands. Unlike benign adenomas, adenocarcinomas show an invasive growth pattern and the potential for metastasis. Histologically, these tumors are characterized by atypical glandular cells that disrupt the normal tissue architecture and can infiltrate the surrounding tissue.
The most important facts at a glance
Cutaneous adenocarcinoma in dogs is a malignant tumor that arises from the glandular structures of the skin and accounts for about 2–6% of all cutaneous neoplasias. These tumors occur predominantly in older dogs and are associated with a certain breed predisposition. The etiology is multifactorial, with genetic factors, environmental influences, and chronic inflammatory processes playing a role.
Clinically, adenocarcinomas present as progressively growing, firm nodules that can ulcerate in advanced stages. Diagnosis is made through a combination of clinical examination, cytological and histopathological examination, and imaging procedures for staging.
The therapy of choice is wide surgical excision with tumor-free resection margins. In cases of incomplete resection or high-grade malignant tumors, adjuvant therapies such as radiation therapy or, in selected cases, chemotherapy may be indicated. Newer therapy approaches such as electrochemotherapy, targeted therapies, and immunotherapeutic procedures expand the therapeutic spectrum.
The prognosis depends significantly on the tumor stage, histological grade, and completeness of surgical resection. Structured follow-up care with regular clinical examinations and imaging studies is essential to detect recurrence or metastases early.
The early detection of Skin changes by the owner and prompt veterinary clarification are crucial for an optimal treatment outcome. Owners should therefore be instructed to perform regular skin examinations on their dog and have changes clarified by a veterinarian immediately.
Causes
Cutaneous adenocarcinomas account for approximately 2–6% of all cutaneous neoplasias in dogs, making them among the rarer skin tumors. They occur predominantly in older dogs, with the average age of onset around 10–12 years. Certain breeds such as Cocker Spaniels, Poodles, and Labrador Retrievers appear to have a certain predisposition, suggesting genetic factors. The biological significance of these tumors lies in their locally aggressive behavior and their ability to metastasize to lymph nodes and distant organs, making them a serious oncological condition.
The etiology of cutaneous adenocarcinomas is multifactorial and not fully understood. Scientific evidence suggests an interplay of various factors:
Genetic predispositions play an important role, as evidenced by the increased occurrence in certain dog breeds. Molecular genetic studies have identified specific genetic alterations, including mutations in tumor suppressor genes and oncogenes, which can contribute to the malignant transformation of glandular cells.
Environmental factors such as chronic UV exposure can contribute to carcinogenesis, particularly in thinly haired or unpigmented skin areas. Long-term exposure to chemical carcinogens in the environment is also considered a possible risk factor.
A particularly important pathogenetic mechanism is the link between chronic inflammatory processes and tumor development. Persistent Skin inflammation can impair DNA repair mechanisms through continuous tissue damage, oxidative stress, and the release of inflammatory mediators, and promote malignant transformation. This explains why non-healing Skin inflammation can pose an increased risk for the development of adenocarcinomas.
Hormonal factors are also discussed as possible influencing factors, particularly in tumors arising from hormone-dependent glandular structures. However, the evidence for this in cutaneous adenocarcinoma is less clear than in other tumor types.
Symptoms
The clinical presentation of cutaneous adenocarcinomas can vary, but shows characteristic features that are recognizable to the pet owner. Typically, these tumors present as solitary, firm Lumps in the skin or in the subcutaneous tissue. Size can range from a few millimeters to several centimeters, with larger tumors often having an irregular surface.
A significant clinical feature is the growth behavior: adenocarcinomas often show progressive growth over weeks to months. In advanced stages, the tumors can ulcerate, which can lead to Bleeding, secretions, and secondary bacterial infections. These complications manifest as weeping, an unpleasant odor, and pain at the affected site.
Affected dogs often show increased Licking or Scratching at the tumor site, indicating local Itching or discomfort. With tumors in mechanically stressed areas such as the paws or in joint regions, Lameness or Limited mobility can occur.
In advanced disease with metastasis, systemic symptoms may occur, including lethargy, inappetence, and Weight loss, and, depending on the location of the metastases, organ-specific symptoms. Enlarged regional lymph nodes may indicate lymphogenous metastasis and should therefore always be carefully palpated.
Particularly problematic are adenocarcinomas that develop from chronic, non-healing inflammatory foci. Here, the transition from chronic dermatitis to a malignant process can be difficult for the owner to recognize, which underscores the importance of regular veterinary examinations for persistent skin changes.
Therapy
Surgical removal of the tumor with a healthy tissue margin.
Radiation therapy or chemotherapy if surgical removal is not possible or in metastatic disease.
Follow-up care for early detection of recurrence / relapse or metastases.
The therapy of cutaneous adenocarcinoma in dogs is based on a multimodal approach, with surgical intervention remaining the most important treatment option. The choice of optimal therapeutic strategy depends on the tumor stage, location, histological grade, and the patient’s general condition.
Surgical excision with wide safety margins (at least 2–3 cm lateral as well as one fascial layer in depth) is the therapy of first choice. The goal is complete removal of the tumor with tumor-free resection margins (R0 resection), as this offers the best prognosis. In unfavorable locations or with large tumors, reconstructive surgical procedures such as local flap plasties or free skin grafts may be required to close the defect.
In cases of incomplete resection (R1 or R2 resection) or high-grade malignant tumors, adjuvant radiation therapy is often recommended. Modern irradiation techniques such as intensity-modulated radiation therapy (IMRT) or stereotactic radiosurgery allow precise application of the radiation dose while sparing the surrounding healthy tissue. Radiation therapy can also be considered as a primary treatment option for inoperable tumors.
Chemotherapy plays a subordinate role in the treatment of cutaneous adenocarcinoma but can be used in metastatic disease or as adjuvant therapy after incomplete resection. Commonly used chemotherapeutic agents include doxorubicin, carboplatin, and cyclophosphamide. However, response rates are variable and often not long-lasting.
Newer therapeutic approaches include:
Electrochemotherapy, in which electrical impulses increase cell membrane permeability, leads to improved intracellular uptake of chemotherapeutic agents. This method has proven effective particularly for superficial tumors.
Targeted therapies that focus on specific molecular changes in tumor cells are gaining increasing importance. Tyrosine kinase inhibitors such as toceranib have shown promising results in some cases.
Immunotherapeutic approaches, including checkpoint inhibitors that activate the body’s own immune system to fight tumor cells, are currently being investigated in clinical trials and could expand the therapeutic arsenal in the future.
When deciding on therapy, the animal’s age, comorbidities, the expected quality of life, and the owner’s financial means must always be taken into account. An open discussion between veterinarian and owner about therapy options, chances of success, and possible side effects is appropriate for well-informed decision-making.
Prognosis and follow-up care
The prognosis for dogs with cutaneous adenocarcinoma is variable and depends on several factors. The most important prognostic factors include the histological grade of the tumor, the tumor stage at the time of diagnosis, the completeness of surgical resection, and the presence of metastases.
With complete surgical removal (R0 resection) of a low- to moderately malignant adenocarcinoma without metastases, the prognosis is comparatively favorable, with median survival times of 12 to 24 months. High-grade malignant tumors, incomplete resections, or the presence of metastases are associated with a significantly poorer prognosis, with median survival time dropping to 6–12 months or less.
Molecular markers such as the expression of certain growth factor receptors or the proliferation rate (Ki-67 index) can provide additional prognostic information and are increasingly being incorporated into prognosis assessment.
Follow-up care after treatment of adenocarcinoma is an essential component of the overall management and includes several components:
Regular clinical examinations are particularly important in the first two years after therapy, as the risk of local recurrence and metastases is highest during this period. Monthly examinations are recommended in the first six months, after which the intervals can be extended to three to four months.
Follow-up examinations should include a thorough clinical examination, with particular attention to the surgical site and the regional lymph nodes. Diagnostic imaging such as X-ray of the thorax / chest and ultrasound of the abdomen are performed at regular intervals (every 3–6 months) to detect metastases early.
In dogs receiving chemotherapy or targeted therapy, regular blood tests are required to monitor possible side effects and adjust the dose.
Wound care after surgical procedures is an important aspect of follow-up care. Owners should be instructed on how to recognize signs of wound-healing disorders or infections and when to seek veterinary help.
Supportive measures to improve quality of life, such as adequate pain therapy / analgesic therapy, an adapted diet, and, if necessary, physiotherapeutic measures, should be integrated into the follow-up concept.
Prevention
For prevention of cutaneous adenocarcinoma, early detection is crucial. Regularly palpating the dog, especially in older animals, allows suspicious lumps to be detected early. Wounds or Skin changes that do not heal within two weeks should be examined by a veterinarian. Excessive sun exposure, especially in dogs with light skin or thin coat, should be avoided. A balanced diet and an intact immune system contribute to skin health. Since genetic factors may play a role, careful breeding selection is important. The earlier a skin tumor is detected, the higher the chances of successful treatment.
Outlook on current research
Research in the field of canine cutaneous adenocarcinomas is continuously evolving and opening up new perspectives for diagnosis and therapy. Current research focuses include molecular characterization, innovative therapy approaches, and improved prognostic markers.
In molecular oncology, genetic and epigenetic alterations in cutaneous adenocarcinomas are increasingly being identified. Using techniques such as next-generation sequencing and proteomics, specific mutations and altered signaling pathways can be characterized that represent potential targets for targeted therapies. Identifying driver mutations, similar to human adenocarcinoma, could enable the development of personalized therapy strategies.
A promising area of research is immuno-oncology. Investigating the tumor microenvironment and the interaction between tumor cells and the immune system has led to the development of new immunotherapeutic approaches. Checkpoint inhibitors, which are already established in human medicine, are increasingly being evaluated in veterinary studies. Initial results show promising response rates in certain tumor entities, although efficacy in cutaneous adenocarcinomas still needs further investigation.
The development of minimally invasive therapy procedures is another research focus. Techniques such as photodynamic therapy, in which light-activated substances selectively destroy tumor cells, or high-frequency thermoablation are being investigated for their applicability in superficial skin tumors.
In diagnostics, advances in diagnostic imaging, such as high-resolution ultrasound procedures, functional MRI techniques, or PET-CT, enable more precise tumor characterization and staging. Liquid biopsy, in which circulating tumor DNA or tumor cells are detected in the blood, could in the future represent a minimally invasive method for tumor diagnosis, therapy monitoring, and detection of recurrence / relapse.
Translational research approaches that transfer findings from human medicine to veterinary medicine are gaining increasing importance. Comparative oncology studies that examine similarities and differences between human and canine tumors can contribute to a better understanding of tumor biology and the development of new therapeutic approaches.
The integration of artificial intelligence and machine learning into oncological diagnostics and therapy planning represents an innovative research approach. Algorithms for automated analysis of histopathological images or for predicting therapy response could support clinical decision-making in the future.
Frequently Asked Questions (FAQs)
1. What is a cutaneous adenocarcinoma in dogs?
2. What symptoms indicate a cutaneous adenocarcinoma?
3. How is the diagnosis made?
4. What Treatment Options are Available?
5. What is the prognosis for cutaneous adenocarcinomas?
6. Can cutaneous adenocarcinomas metastasize in dogs?
7. What role does the breed play?
8. How can I prevent cutaneous adenocarcinomas?
9. What does aftercare look like?
10. Can a dog continue to live a normal life after the removal of a cutaneous adenocarcinoma?
Literature
- Goldschmidt, M. H., & Goldschmidt, K. H. (2017). Epithelial and melanocytic tumors of the skin. In D. J. Meuten (Ed.), Tumors in domestic animals (5th ed., pp. 88–141). Wiley Blackwell. https://doi.org/10.1002/9781119181200.ch4
- Martins, A. L., Canadas-Sousa, A., Mesquita, J. R., Dias-Pereira, P., Amorim, I., & Gärtner, F. (2022). Retrospective study of canine cutaneous tumors submitted to a diagnostic pathology laboratory in Northern Portugal (2014–2020). Canine Medicine and Genetics, 9, Article 2. https://doi.org/10.1186/s40575-022-00113-w
- Tangchang, W., Jung, G.-y., Song, J.-y., Kumbukgahadeniya, P., Kim, D.-h., Kwon, H.-j., & Son, H.-y. (2024). Endocrine mucin-producing sweat gland carcinoma (EMPSGC) in a dog: Immunohistochemical characterization. Animals, 14(24), 3637. https://doi.org/10.3390/ani14243637
- Moon, C.-H., Min, H.-A., Lee, H.-B., Jeong, S.-M., & Kim, D.-H. (2022). Retroperitoneal metastatic apocrine gland ductal adenocarcinoma in a Beagle dog. Veterinary Sciences, 9(5), 234. https://doi.org/10.3390/vetsci9050234
- Akhtardanesh, B., Kheirandish, R., Dabiri, S., Azari, O., Vosoogh, D., & Askari, N. (2012). Metastatic apocrine sweat gland adenocarcinoma in a terrier dog. Asian Pacific Journal of Tropical Biomedicine, 2(8), 670–672. https://doi.org/10.1016/S2221-1691(12)60118-X
- Kato, K., Uchida, K., Nibe, K., & Tateyama, S. (2007). Immunohistochemical studies on cytokeratin 8 and 18 expressions in canine cutaneous adnexus and their tumors. Journal of Veterinary Medical Science, 69(3), 233–239. https://doi.org/10.1292/jvms.69.233
- Schulman, F. Y., Lipscomb, T. P., & Atkin, T. J. (2005). Canine cutaneous clear cell adnexal carcinoma: Histopathology, immunohistochemistry, and biologic behavior of 26 cases. Journal of Veterinary Diagnostic Investigation, 17(5), 403–411. https://doi.org/10.1177/104063870501700501
- Simko, E., Wilcock, B. P., & Yager, J. A. (2003). A retrospective study of 44 canine apocrine sweat gland adenocarcinomas. The Canadian Veterinary Journal, 44(1), 38–42.
- Kalaher, K. M., Anderson, W. I., & Scott, D. W. (1990). Neoplasms of the apocrine sweat glands in 44 dogs and 10 cats. Veterinary Record, 127(16), 400–403.