Granulomatous Lobular Mastitis: A Rare Case of Erythema Nodosum

Sir,

Granulomatous lobular mastitis (GLM) and mammary duct ectasia (MDE) are inflammatory breast diseases with moderately low incidence rates whose etiology and pathogenesis remain unclear. Erythema nodosum (EN) can manifest as an extramammary symptom of GLM during a patient’s disease course.

A 40-year-old female presented with several palpable nodules in her left breast discovered four months prior. Initial treatment with penicillin and tinidazole for six days yielded no significant improvement. Subsequently, symmetrical red nodules developed on both knees, escalating in severity and accompanied by pain. The patient’s medical history included hypertension for three years, menarche at 12 years, two childbirths, no familial breast cancer history, and no use of oral contraceptives. Physical Examination: An oval mass of approximately 10 cm × 4 cm was palpable in the left breast, with smooth overlying skin. Several erythematous and nodular lesions ranging from peanut to palm-sized were noted on the extensor sides of both calves, characterized by tenderness, slightly elevated skin temperature, and absence of necrosis or ulceration [Figure 1]. Diagnostic Findings: Mammography revealed dilated ducts in the left breast (BI-RADS 2) without abnormal axillary lymph nodes. Pathological examination via puncture biopsy identified inflammatory lesions in the mammary glands with significant neutrophil, lymphocyte, and histiocyte infiltration. Skin pathology of the lower extremities was consistent with erythema nodosum. Treatment: The patient received oral methylprednisolone (20 mg daily), antibiotics, and other supportive treatments. Improvement in the lower extremity rash and pain was noted after one week, leading to discharge with continued oral therapy. However, the left breast mass worsened, prompting surgical intervention [Figure 2]. A left quadrant mastectomy and fascial tissue flap plasty were performed. Postoperative pathology revealed multiple inflammatory cell infiltrates and granulomas, with neutrophildominant small abscess formation and fibrous thickening of the mammary duct walls surrounded by lymphocytes and plasma cells [Figure 3]. Follow-up: One-month post-surgery, the patient exhibited a 15 cm linear scar on the left breast and residual light brown discoloration on both lower extremities.

Figure 1.

Erythema nodosum in the lower legs

Figure 2.

Multiple superficial erosions located on the left breast

Figure 3.

H and E, original magnification: 100×. (a) Postoperative pathology showed that there were multiple inflammatory cell infiltrates and granulomas around the absorbing vacuoles in the lobules with predominantly neutrophils, and small abscess formation. (b) Dilated mammary ducts with fibrous thickening of the ductal walls surrounded by inflammatory infiltrates with predominantly lymphocytes and plasma cells

GLM predominantly affects women of childbearing age and usually presents with breast pain, skin erythema, swelling, and potentially skin breakdown, representing 24% of all inflammatory breast conditions.[1] GLM is thought to result from milk stagnation leading to an inflammatory reaction in the mammary gland, triggering a localized immune response characterized by lymphocyte, plasma cell, and phagocyte infiltration and granuloma formation. This process can destroy normal milk ducts, perpetuating a cycle of inflammation and further ductal damage.[2] Research on the coexistence of GLM and MDE is limited, but evidence suggests that GLM-related secretion retention may initiate periductal inflammation and fibrosis, leading to ductal dilatation.[3] EN and other extramammary manifestations like inflammatory arthritis in GLM patients indicate an underlying immune process.[4] Studies have shown that GLM patients with EN experience more severe symptoms, including fever, longer disease duration, higher recurrence risk, and extensive lesion spread.[5] These findings suggest a poorer prognosis for GLM patients with EN. Our case highlights extensive granulomatous lobular mastitis with nodular erythema and ductal dilatation, progressing to EN, possibly due to a delayed hypersensitivity reaction. The successful treatment of GLM and EN in this case, with surgical excision and glucocorticoid therapy, underscores the potential immune mechanism underlying these conditions. Hormonal treatment led to the resolution of nodular erythema and surgical intervention improved breast tumors without observed recurrence, reinforcing the immune-mediated nature of these diseases.

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Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.