Scalp Schwannoma Masquerading as a Pilar Cyst
Poster #: 049
Session/Time: B
Author:
Kenjy Li Cruz-Ham, BS
Mentor:
Alberto E. Musto, MD, PhD
Research Type: Case Report
Abstract
INTRODUCTION:
Scalp masses are frequently encountered in dermatology and primary care, with pilar cysts and epidermal inclusion cysts being a common diagnosis. Schwannomas are benign peripheral nerve sheath tumors that are rarely found in the scalp and are often overlooked due to their nonspecific clinical presentation. Their resemblance to the common pilar (trichilemmal) cyst may lead to misdiagnosis and unexpected findings on pathology. This case highlights the importance of histopathological, immunohistochemical evaluation, including schwannoma in one's differential, ensuring diagnostic accuracy and safe management.
CASE INFORMATION:
A 21-year-old male with no significant past medical history presented with a slowly enlarging, mobile, subcutaneous nodule on the right vertex scalp. The lesion was initially diagnosed clinically as a pilar (trichilemmal) cyst by a separate clinician two months prior. The patient reported mild discomfort associated with the lesion, which had been present for two years. Relevant family history included skin cancer in both paternal and maternal grandfathers. On examination, the lesion measured 1.5 cm, was firm but nontender, and showed no overlying skin changes, alopecia, or inflammation. The patient underwent a standard procedure for cases like these, excision under local anesthesia. Gross pathology revealed a 1.0 x 1.0 x 0.9 cm tan nodule. Histological evaluation demonstrated interlacing bundles of spindle cells with elongated, tapered nuclei. Immunohistochemical staining showed strong S100 positivity and actin negativity, confirming schwannoma. The patient recovered uneventfully, and follow-up at two weeks showed complete healing without recurrence.
DISCUSSION/CLINICAL FINDINGS:
This case demonstrates the diagnostic challenge of distinguishing schwannomas from more common scalp lesions based solely on clinical features. The lesion's appearance and mobility were consistent with a benign cyst, underscoring the risk of misclassification in the absence of histological evaluation. Scalp schwannomas, though rare, should be considered in the differential diagnosis for subcutaneous nodules, particularly when lesions are long-standing, slowly enlarging, or atypical in presentation. The patient's family history of skin cancer, while not directly related to schwannoma, added clinical relevance in the context of evaluating scalp masses. Histopathology remains the diagnostic gold standard, and immunohistochemical staining further aids in confirming the neural origin of the lesion.
CONCLUSION:
This schwannoma presentation is a rare case in dermatology; it is important to include it in the differential diagnosis of scalp masses that appear clinically benign. Early recognition ensures accurate surgical management, which can be especially dangerous if not diagnosed as one while doing a procedure. Definitive diagnosis requires histopathological and immunohistochemical confirmation. Overall, using modalities like these prevents complications while providing valuable learning opportunities for clinicians and residents to maintain a broad differential of such rare cases when evaluating scalp lesions.
Scalp masses are frequently encountered in dermatology and primary care, with pilar cysts and epidermal inclusion cysts being a common diagnosis. Schwannomas are benign peripheral nerve sheath tumors that are rarely found in the scalp and are often overlooked due to their nonspecific clinical presentation. Their resemblance to the common pilar (trichilemmal) cyst may lead to misdiagnosis and unexpected findings on pathology. This case highlights the importance of histopathological, immunohistochemical evaluation, including schwannoma in one's differential, ensuring diagnostic accuracy and safe management.
CASE INFORMATION:
A 21-year-old male with no significant past medical history presented with a slowly enlarging, mobile, subcutaneous nodule on the right vertex scalp. The lesion was initially diagnosed clinically as a pilar (trichilemmal) cyst by a separate clinician two months prior. The patient reported mild discomfort associated with the lesion, which had been present for two years. Relevant family history included skin cancer in both paternal and maternal grandfathers. On examination, the lesion measured 1.5 cm, was firm but nontender, and showed no overlying skin changes, alopecia, or inflammation. The patient underwent a standard procedure for cases like these, excision under local anesthesia. Gross pathology revealed a 1.0 x 1.0 x 0.9 cm tan nodule. Histological evaluation demonstrated interlacing bundles of spindle cells with elongated, tapered nuclei. Immunohistochemical staining showed strong S100 positivity and actin negativity, confirming schwannoma. The patient recovered uneventfully, and follow-up at two weeks showed complete healing without recurrence.
DISCUSSION/CLINICAL FINDINGS:
This case demonstrates the diagnostic challenge of distinguishing schwannomas from more common scalp lesions based solely on clinical features. The lesion's appearance and mobility were consistent with a benign cyst, underscoring the risk of misclassification in the absence of histological evaluation. Scalp schwannomas, though rare, should be considered in the differential diagnosis for subcutaneous nodules, particularly when lesions are long-standing, slowly enlarging, or atypical in presentation. The patient's family history of skin cancer, while not directly related to schwannoma, added clinical relevance in the context of evaluating scalp masses. Histopathology remains the diagnostic gold standard, and immunohistochemical staining further aids in confirming the neural origin of the lesion.
CONCLUSION:
This schwannoma presentation is a rare case in dermatology; it is important to include it in the differential diagnosis of scalp masses that appear clinically benign. Early recognition ensures accurate surgical management, which can be especially dangerous if not diagnosed as one while doing a procedure. Definitive diagnosis requires histopathological and immunohistochemical confirmation. Overall, using modalities like these prevents complications while providing valuable learning opportunities for clinicians and residents to maintain a broad differential of such rare cases when evaluating scalp lesions.