Title : Anterior knee schwannoma: An atypical location and presentation of lower extremity schwannoma
Abstract:
Background: Schwannomas, benign tumors originating from Schwann cells, are a relatively uncommon occurrence within the realm of peripheral nerve tumors. However, the manifestation of a schwannoma in the anterior knee region is an even rarer phenomenon, with only a limited number of documented cases in the existing medical literature.
Patient History: A 24-year-old female sought consultation with a dermatologist due to the presence of a slow-growing superolateral knee mass. The mass, which had been progressively enlarging over a period of three years, exhibited characteristics of being mobile, firm, spherical, and devoid of tingling, radiation, or sharp pain. The patient reported minimal pain without radiation, specifically when the knee was subjected to soft external stimuli. The dermatologist suspected the patient had a lipoma or an epidermal cyst. The patient’s mother has a history of keloid, therefore surgical options need to be carefully decided with labs and test results.
Treatment Plan: Upon examination, an orthopedic surgeon recommended excision of the mass under local anesthesia. The decision for surgical intervention was driven by the suspicion of the mass being attached to the bone.
Results of Pathology Testing: Pre-operative imaging, specifically magnetic resonance imaging (MRI), revealed a soft tissue mass composed of multiple cystic structures.
Biopsies: ‘Left knee soft tissue mass’ received on formalin is a tan, partially encapsulated, soft tissue mass measuring 2.0 x 1.6 x 1.0 cm. The exterior surface is inked blue. The specimen is serially sectioned, revealed a tan, gelatinous, well-circumcised lesion occupied the entire specimen. The specimen is entirely and sequentially submitted across cassettes A1 and A2.
Laboratory Data: Microscopic examination of the biopsied tissue revealed a well-defined proliferation of spindled cells, showcasing Verocay bodies with distinct Antoni A and Antoni B areas. Importantly, there were no identified atypical nuclei or increased mitotic activity, contributing to the characterization of the lesion as benign.
Diagnosis: Based on the comprehensive pathology findings, the conclusive diagnosis for the
presented case is an anterior knee schwannoma. The rarity of this specific location for a schwannoma underscores the uniqueness of the patient's condition, necessitating further exploration into the clinical implications and management strategies for such atypical presentations. The patient's surgical scar developed into a keloid, which might be due to genetics. Early intervention and recommendation by the provider would have resulted in a smaller surgical scar which would result in a smaller keloid scar and faster treatment.
Audience Take Away Notes:
- Experts in Dermatology would be able to learn about an unusual presentation of schwannoma that may confound the diagnosis and delay treatment. Although schwannomas are benign, as they grow they can impinge the nerves. Learning from this abstract, providers can keep an eye out for unusual abnormalities and avoid misdiagnoses
- The patient presented the abnormality to her dermatologist and was misdiagnosed as a lipoma or a cyst
- This research can be expanded on with other cases of growth that mimic a lipoma or a cyst. The patient in this case presentation also is under treatment because the surgery scar turned into a keloid, most likely due to genetics but it would be interesting to see if the surgical removal of schwannomas has been linked to an increased risk of keloid formation
- The best solution for anterior knee schwannomas that grow to an uncomfortable size is surgical removal, but if the patient was diagnosed earlier as she has a family history of keloid, the surgical scar would be smaller. In that case, her keloid would be much smaller and easier to fix. Therefore, early and accurate diagnoses of growing lesions is important
- This will improve accuracy as more cases will be found of schwannomas that mimic lipomas
- The benefits to this study are accurate diagnoses, early intervention, early prevention of scar formation, and patient satisfaction
