Metastatic breast involvement from Merkel cell tumour: a case report
Sophie Winge, Katrine Jensen
Contributions: (I) Conception and design: Both authors; (II) Administrative support: Both authors; (III) Provision of study materials or patients: Both authors; (IV) Collection and assembly of data: Both authors; (V) Data analysis and interpretation: Both authors; (VI) Manuscript writing: Both authors; (VII) Final approval of manuscript: Both authors.
Background: Merkel cell carcinoma (MCC) is an uncommon and aggressive skin cancer, very rarely metastasising to the breast. MCC metastases to the breast with known primary tumour have earlier been reported in the literature, but never as seen in this case, where a metastasis is found in an intramammary lymph node and where primary tumour could not be localised. This case adds to the existing literature with new insights to MCC presentation into a male patient.
Case Description: We present a case of a 64-year-old man with a small palpable tumour in his right breast persistent for 2 weeks and no other symptoms associated with cancer. The patient had a history of aorto-coronary bypass grafting and replacement of the aortic valve, hypertension, and a dilated aorta, but was asymptomatic and working his job daily. The patient was examined by a breast surgeon and referred for mammography, ultrasound, and biopsy. Ultrasound-guided biopsy was carried out and final pathology report revealed a MCC metastasis in an intramammary lymph node. Positron emission tomography/computed tomography (PET/CT) scan identified an area in the gastric ventricle with thickened wall, but could not identify any primary tumour, since biopsies from the gastric ventricle was without cancer. The patient was followed up by the plastic surgeons with no skin signs of MCC and followed up continuously with PET/CT every 3 months.
Conclusions: MCC metastasis to the breast has been reported casuistically before, but this case presents a MCC metastasis in an intramammary lymph node with an unknown primary tumour which has not been reported before. This case adds to the many and unpredictable ways a MCC metastasis can present itself clinically, suggesting that diagnosis may be difficult. With this case, we also emphasize the importance of a breast surgeon’s clinical skills in distinguishing between tumours thought benign and tumours that should be biopsied, since a small soft lump in the male breast or chest region can easily be mistaken for gynecomastia or lipoma by an untrained eye, and therefore further interventions dismissed. The takeaway message from this case report is, that breast examination should be considered part of the routine follow-up not only for women but also for men with MCC.
Keywords: Case report; Merkel cell tumour; metastatic breast involvement; intramammary lymph node; follow up
Received: 29 April 2024; Accepted: 02 August 2024; Published online: 30 September 2024.
doi: 10.21037/abs-24-27
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Key findings
• Metastasis from a Merkel cell tumour to the male breast where primary tumour could not be found.
What is known and what is new?
• Merkel cell carcinoma (MCC) is an uncommon and aggressive skin cancer, very rarely metastasising to the breast. MCC metastases to the breast with known primary tumour have earlier been reported in the literature, but never as seen in this case, where a metastasis is found in an intramammary lymph node and where primary tumour could not be localised.
• This case adds to the existing literature with new insights into MCC presentation in a male.
What is the implication, and what should change now?
• In this case, we emphasize the importance of a breast surgeon’s clinical skills in distinguishing between tumours thought benign and tumours that should be biopsied. The takeaway message from this case report is, that breast examination should be considered part of the routine follow-up not only for women but also for men with MCC.
Introduction
Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer with neuroendocrine features. It typically presents as a rapidly growing, painless, firm nodule on sun-exposed areas of the skin. MCC most commonly affects immunocompromised and elderly individuals with fair skin and a history of significant sun exposure (1). While the primary site is usually the skin, arousal in and metastases to regional lymph nodes, distant organs, and unusual sites can occur (2-4). Metastases to the breast from MCC are exceptionally rare, with only a few cases reported in the literature (5,6). A MCC metastasis in an intramammary lymph node with an unknown primary tumour has not previously been reported. We present this case in accordance with the CARE reporting checklist (available at https://abs.amegroups.com/article/view/10.21037/abs-24-27/rc).
Case presentation
Patient information
We present a case of a 64-year-old man, a former smoker known with hypertension, chronic heart disease and bypass surgery, and insertion of a mechanical aortic valve. The patient had a two-week history of a palpable tumour in his right breast and did not present any other symptoms associated with cancer. The patient was working as a carpenter. The patient was concerned that the tumour could represent breast cancer.
Clinical findings
The patient was seen in the outpatient clinic by a certified breast surgeon who found a 10 mm × 0.5 mm palpable process in the upper lateral quadrant near to the nipple-areolar complex and could not rule out malignancy by clinical examination. There were no skin lesions or discoloration. The process was located 2–3 mm under the skin. The tumour is marked with black pen on the skin (Figure 1).
Diagnostic assessment
The localisation and firmness of the tumour did not resemble gynaecomastia or lipoma, and therefore the patient was referred to mammography and ultrasound of the breasts which revealed a solid cystic process of 11 mm × 2 mm (Figure 2). An ultrasound-guided core needle biopsy was performed and revealed metastasis from neuroendocrine tumour, most likely originating from the gastrointestinal tract.
The patient was examined via the Department of Gastrointestinal Surgery with blood tests, positron emission tomography/computed tomography (PET/CT) scan, gastroscopy and colonoscopy. The PET/CT showed wall thickening of the gastric ventricle otherwise nothing else was abnormal (Figure 3). Gastroscopy and endoscopic ultrasound (EUS) with biopsies from the gastric ventricle showed no malignancy and colonoscopy was normal.
A pathological review was then carried out, which raised the suspicion of MCC, but due to insufficient material from the first biopsy of the breast tumor, a radioactive seed marker was placed in the tumour, and diagnostic excision of the tumor was performed (Figure 4). The result showed metastatic MCC in an intramammary lymph node. Immunohistochemical stains of the lumpectomy specimen demonstrated positive synaptophysin and chromogranin, consistent with MCC.
The patient was referred to the Department of Plastic Surgery and the Oncological Department for multidisciplinary discussion of treatment and follow up.
The skin organ was examined by a plastic surgeon without findings of a primary tumor or any other suspicious skin changes or wounds. Again, a whole-body PET/CT was performed to rule out disseminated disease as well as in search of the primary tumor. It showed no signs of any malignancies.
Therapeutic intervention
The Oncological Department recommended no further surgery or radiation therapy corresponding to the metastatic field since the lymph node was removed with clear margins, and it was confirmed that it was a metastasis and not the primary tumour. A regular follow-up process was recommended with clinical examination every third month preceded by a PET/CT to be conducted over the next two years and thereafter every sixth month.
Follow-up and outcomes
PET/CT three months after first PET/CT showed no signs of malignancy and the patient still had no clinical symptoms indicating cancer.
Timeline
From patient was first seen in the breast surgery department until final diagnosis of tumour in the breast was made, 81 days passed. Providing a diagnosis was protracted by revision of the pathology specimen and due to loss of biopsies from the gastric ventricle. Figure 5 provides an overview.
Patient perspective
The patient was frustrated that the first biopsy from the breast could not give a specific diagnosis, and surgery had to be performed to remove the process for a clear pathological result. He was further distressed that a primary tumour had not been found yet and that he developed a surgical site infection (Figure 6), and that the first biopsies from the gastric ventricle was lost. He was grateful to receive scans and clinical assessment regularly onwards.
Ethical statement
All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.
Discussion
MCC is known for its aggressive behaviour and propensity for early metastases. Lymph nodes, liver, lungs, and bones are the most common sites of metastatic involvement (1). However, breast involvement is an extremely rare finding, but primary MCC of the breast is seen (3,4,6-8). The mechanism of metastasis to the breast remains unclear, but it is likely related to hematogenous spread or lymphatic dissemination (2).
The diagnosis of metastatic MCC in the breast requires a high index of suspicion and teamwork with several departments being involved, especially a subspecialised pathologist reviewing the specimen in case of doubt. Imaging studies and a biopsy play a crucial role in confirming the diagnosis. Treatment options for metastatic MCC include surgery, radiation therapy, chemotherapy, immunotherapy, and targeted therapy, depending on the extent and location of metastatic disease (1,9).
This case report complements other research approaches and results and can act as an educational tool for MCC and tumours in the breast, allowing emphasis on the narrative aspect, and educational value. The major limitations are the lack of ability to generalize, no possibility to establish cause-effect relationship, the retrospective design, and that it may cause a distraction for the inexperienced reader in focusing on an unusual presentation.
The takeaway message from this case report is that breast examination should be considered part of the routine follow-up not only for women but also for men with MCC.
Conclusions
This case presents an unusual metastatic site of a MCC in the breast of a male patient. Although rare, metastases to the breast can occur, and early detection is crucial for appropriate management. Healthcare professionals should maintain a high index of suspicion and include breast evaluation as part of the routine follow-up for patients with MCC. This case also implies the importance of a breast surgeon’s experience in evaluating palpable tumours in the breast and to distinguishing between tumours thought benign and tumours that should be biopsied, since a small soft lump in the male breast or chest region can easily be mistaken for gynecomastia or lipoma by an untrained eye, and therefore further interventions dismissed. Further research is needed to better understand the underlying mechanisms and optimal treatment strategies for metastatic MCC involving the breast.
Acknowledgments
None.
Footnote
Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://abs.amegroups.com/article/view/10.21037/abs-24-27/rc
Peer Review File: Available at https://abs.amegroups.com/article/view/10.21037/abs-24-27/prf
Funding: None.
Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://abs.amegroups.com/article/view/10.21037/abs-24-27/coif). The authors have no conflicts of interest to declare.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.
Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
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Cite this article as: Winge S, Jensen K. Metastatic breast involvement from Merkel cell tumour: a case report. Ann Breast Surg 2025;9:7.
