Rheumatologic Dermatology and Breast Cancer: What Every Dermatologist Should Know

Skin serves as both a window into systemic disease and a source of diagnostic pitfalls. In autoimmune disease, the challenge is bidirectional: Conditions can masquerade as breast cancer, while malignancy can mimic inflammatory dermatoses. Rheumatologic-dermatologic conditions may arise as paraneoplastic phenomena,¹ be triggered by cancer therapies,² or clinically mimic breast cancer.³ Herein, we discuss potential challenges that might be seen in any dermatologist’s office.

Lupus Mastitis

Lupus mastitis, a rare manifestation of cutaneous lupus, presents as firm subcutaneous breast masses or plaques with calcification seen on imaging. Clinically and radiographically, it is often indistinguishable from breast carcinoma without histopathology. Case reports describe patients presenting with peau d’orange-like skin changes concerning for breast carcinoma, which are found to be caused by lupus mastitis only after a skin biopsy.^3,4

Hypothetically, the reverse scenario could also occur, wherein an inflammatory breast malignancy could be mistaken for lupus mastitis in a woman with known systemic lupus. Therefore, it is our recommendation to biopsy any atypical breast mass/plaque in a patient with lupus. Hydroxychloroquine is the recommended first-line treatment for lupus mastitis, though other immunomodulatory medications can be considered.⁵

Radiation-Induced Morphea

Radiation-induced morphea (RIM) develops months to years after radiation therapy. It can manifest as circumscribed inflammation, sclerosis, and edema within the radiation field.⁶ For breast cancer survivors, these cutaneous changes are often immediately concerning for recurrence.

From a dermatologist’s perspective, astute consideration of breast radiation history in patients presenting with new breast skin changes can aid in the diagnosis of RIM. Immediate treatment of RIM minimizes the risk of irreversible fibrosis, preserving quality of life for these patients. Recommended treatment includes methotrexate, intralesional and systemic corticosteroids, mycophenolate mofetil, and other immunomodulating therapies. A brief trial of conservative measures, including topical agents and phototherapy, can be considered for superficial or limited cases.⁷

Extragenital Lichen Sclerosus

Lichen sclerosus (LS) classically affects the genitalia but may also involve the skin beyond.⁸ In our experience from the rheumatologic-dermatology clinic, extragenital LS commonly involves the breasts. Extragenital LS has no direct association with malignancy, though genital LS has a small established risk of malignancy.⁹ Therefore, the masquerade in the context of breast cancer is mostly unidirectional. Ivory-white, atrophic plaques associated with pigment change or surrounding lilac erythema may mimic Paget disease or cutaneous inflammatory breast cancer. LS may also arise in radiated areas as a result of Koebner phenomenon.¹⁰ When malignancy must be ruled out, a biopsy is advised, though it is important to note that histopathologic findings of extragenital LS can be subtle. LS is treated with high-potency topical corticosteroids such as clobetasol once daily until remission and then tapered to the lowest frequency for effective maintenance; topical calcipotriene is a common steroid-sparing agent utilized.¹¹

Dermatomyositis

As one of the most clinically important autoimmune diseases linked to malignancy, dermatomyositis (DM) in the setting of breast cancer must be discussed. Bidirectionally, patients with new-onset DM should receive appropriate cancer screening, including annual breast cancer screening for women, while patients with established malignancies should be monitored for clinical signs of DM, including heliotrope rash and Gottron papules. Dermatologists managing DM should generally have a higher suspicion for underlying malignancy when skin disease is rapid in onset, refractory to therapy, or cutaneous ulcerations/necrosis are seen. Other risk factors include older age at onset, male sex, dysphagia, and certain autoantibodies (TIF1-γ, NXP2). Rarely, a rash of the breast/chest wall (in a V sign) can appear similarly to inflammatory breast cancer or dermal metastases.¹² Conversely, inflammatory breast cancer could present with erythema that resembles cutaneous DM, though this would be rare. Management of DM can be complex and dependent on the presence of myositis, malignancy, arthritis, and lung disease. Intravenous immunoglobulin is the only FDA-approved therapy for DM, though immunomodulating agents can be effective. Photoprotection is advised for all.¹³

Importantly, anti-PD1/PD-L1 therapies are well known to precipitate cutaneous autoimmune diseases. Cutaneous DM is not immune. However, should such a therapy be warranted to treat breast cancer or any other malignancy in a patient with established DM, we recommend proceeding with therapy, along with close monitoring.

Conclusions

The overlap of rheumatology, dermatology, and breast oncology creates unique diagnostic challenges. For dermatologists, we advise keeping both inflammatory dermatologic conditions and malignancies in mind, obtaining a biopsy when uncertainty exists, and communicating across disciplines when appropriate. Dermatologists are often the first to recognize skin changes; timely biopsy, imaging, and/or referral are imperative. Early recognition and collaboration can not only prevent misdiagnoses but also improve outcomes for patients navigating the intersection of cancer, autoimmunity, and skin.

Ellee Pisey Vikram is a third-year medical student at the University of California, Irvine School of Medicine in Irvine, California.

Michelle S. Min, MD, MSci, is an associate professor and director of rheumatologic dermatology at the University of California, Irvine School of Medicine in Irvine, California.

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