Follicular Lymphoma Detected in a Patient Undergoing Mohs Surgery: A Case Report.

Mohs surgery is performed by surgeons trained in detecting specific cutaneous malignancies, including basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and dermatofibrosarcoma protuberans (DFSP). Mohs-trained surgeons are typically not holistic pathologists and may, when working in isolation, fail to identify lesions that are not of cutaneous origin. The presence of a second lesion adjacent to the primary lesion is always a possibility. Such a lesion may be misinterpreted as an extension of the identified primary lesion, leading to unnecessary surgery, or it may be overlooked, resulting in a diagnostic failure. There is an advantage to conducting Mohs surgery with the surgeon and histopathologist reviewing the frozen section slides together, as this approach can aid in the identification of rarer diagnoses. Here, we describe the case of a female patient who underwent Mohs micrographic surgery (MMS) for a recurrent BCC located in the left preauricular area and medial helical rim of the pinna. The surgery involved two excisional stages. The first stage showed morphoeic BCC at all levels of all blocks. The second stage showed no BCC but revealed a dense inflammatory infiltrate. On further assessment by the consultant histopathologist, this infiltrate raised suspicion of possible lymphoma. Based on this consensus, no further Mohs excisional surgery was performed, and the surgical defect was closed. Formalin-fixed paraffin-embedded (FFPE) histological assessment and immunohistochemistry confirmed the diagnosis of cutaneous B-cell follicular lymphoma (FL). Thus, the incidental finding on the examination of fresh frozen MMS sections was correctly interpreted by the combined approach of the Mohs surgeon and pathologist, guiding appropriate and timely management for the patient.