Scalp Lesions: Rare Malignancies Mimic Benign Conditions

Sebaceous carcinoma (SC) is a rare malignant tumor originating from skin appendages.^1,2,3 While most cases occur in the periocular region, extraocular SC accounts for only about 25% of cases.^1,2,3 Scalp involvement is especially rare.^1,2,3 The absence of characteristic clinical features in extraocular SC frequently leads to misdiagnosis as benign lesions, such as epidermal cysts.^1,2,3

Case Reports on Scalp Lesions

A 36-year-old male presented with an atypical extraocular SC in the occipital region.¹ This case initially received a clinical diagnosis of a pilar cyst, which was subsequently revised to sebaceous carcinoma.¹ The presentation underscored the diagnostic challenges and clinical importance of considering SC in scalp lesions.

Another case involved an elderly patient with medical avoidance who presented with a neglected cutaneous clear-cell squamous cell carcinoma of the scalp.² This highlights that even common malignancies can present atypically or be advanced due to delayed presentation.

Leukemia cutis, a manifestation of acute myeloid leukemia (AML), can also present as a cutaneous lesion.³ A case report described leukemia cutis in a patient with AML, emphasizing the need to consider systemic hematological malignancies in the differential diagnosis of skin lesions, particularly in the context of underlying systemic disease.³

These cases collectively demonstrate that ulcerated scalp lesions, even those initially appearing benign or non-specific, necessitate careful evaluation to exclude rare but aggressive malignancies. The lack of distinct clinical features for conditions like extraocular SC contributes to diagnostic challenges, making biopsy and histopathological examination critical for accurate diagnosis and timely management.^1,2,3

The diagnostic dilemma is further compounded by the varied histological presentations of these rare malignancies. For instance, extraocular SC can mimic other adnexal tumors or even poorly differentiated squamous cell carcinoma, requiring careful immunohistochemical staining to confirm its sebaceous differentiation. Similarly, clear-cell squamous cell carcinoma, while a variant of a common malignancy, can present with atypical cytological features that obscure its true nature, necessitating a high index of suspicion and specialized staining techniques to differentiate it from other clear-cell neoplasms.

Leukemia cutis, on the other hand, presents a unique challenge as its cutaneous manifestations can be highly pleomorphic, ranging from papules and nodules to plaques and ulcers. The infiltrative nature of leukemic cells within the dermis can mimic inflammatory dermatoses or other neoplastic processes. Therefore, a thorough clinical history, including any systemic symptoms suggestive of hematological malignancy, is paramount. Biopsy of suspicious skin lesions in this context should be accompanied by immunohistochemical analysis for myeloid markers to confirm the diagnosis and guide systemic treatment.

Clinical Implications and Diagnostic Strategies

Given the potential for misdiagnosis and delayed treatment, healthcare professionals, particularly dermatologists, primary care physicians, and oncologists, must maintain a heightened awareness of these rare scalp malignancies. A low threshold for biopsy is crucial for any persistent, non-healing, or atypical scalp lesion, especially those that do not respond to conventional treatments or exhibit rapid growth. Full-thickness excisional biopsy with clear margins is often preferred for definitive diagnosis and initial management, allowing for comprehensive histopathological and immunohistochemical evaluation.

For extraocular SC, sentinel lymph node biopsy may be considered in cases with high-risk features due to its potential for regional lymph node metastasis. Regular follow-up is also essential for these patients, given the risk of local recurrence and distant metastasis. In the case of clear-cell squamous cell carcinoma, aggressive surgical excision with Mohs micrographic surgery may be indicated to ensure complete tumor removal while preserving surrounding healthy tissue. For leukemia cutis, the diagnosis of the skin lesion often prompts or confirms the diagnosis of the underlying systemic leukemia, necessitating immediate collaboration with hematology-oncology for systemic chemotherapy.

Furthermore, patient education plays a vital role in early detection. Patients, especially those with risk factors such as immunosuppression, previous radiation exposure, or a history of other malignancies, should be advised to report any new or changing scalp lesions promptly. The cases presented underscore the importance of a multidisciplinary approach involving dermatologists, pathologists, surgeons, and oncologists to ensure accurate diagnosis and optimal management of these challenging scalp lesions.