Isolated subcutaneous sarcoidosis presenting as multiple nodules: a rare case with diagnostic challenges.

Introduction and importance: Isolated subcutaneous sarcoidosis is an uncommon form of sarcoidosis, typically presenting as firm, painless nodules beneath clinically normal skin. Its rarity, especially in male patients or in atypical anatomical locations, can mimic malignant or infectious processes and cause significant diagnostic uncertainty. Recognizing this entity is important to prevent misdiagnosis and unnecessary interventions. Case presentation: A 51-year-old man presented with multiple progressively enlarging subcutaneous nodules over the scalp, face, trunk, and extremities for 1 year, without systemic symptoms. Imaging demonstrated well-defined subcutaneous soft-tissue lesions with no bony involvement. Fine-needle aspiration and core biopsy revealed non-caseating granulomas composed of fibrohistiocytic and multinucleated giant cells. Immunohistochemistry showed CD68 and S100 positivity, CD1a negativity, and a low Ki-67 index, confirming isolated subcutaneous sarcoidosis. A comprehensive evaluation found no systemic involvement at presentation. Clinical discussion: Subcutaneous sarcoidosis is rare and may closely resemble neoplastic or infectious conditions, particularly when presenting in unusual distributions or in male patients. Diagnosis relies on histopathologic confirmation of non-caseating granulomas, supported by immunohistochemical findings. Management should be individualized; options include observation for asymptomatic cases and topical or systemic corticosteroids for progressive or symptomatic lesions. Long-term monitoring is essential because systemic manifestations may develop later. Conclusion: This case highlights the importance of considering isolated subcutaneous sarcoidosis in the differential diagnosis of firm, painless nodules. Accurate diagnosis depends on histopathology and immunohistochemistry, and tailored management with ongoing follow-up is recommended. Reporting rare presentations broadens understanding of the clinical spectrum of sarcoidosis and ultimately supports timely, appropriate, and effective comprehensive patient care.