Amyloidosis represents a group of rare diseases characterized by extracellular deposition of insoluble amyloid fibrils. A 57-year-old female patient presented with a well-delimited, asymptomatic, submucosal fibrous nodule, measuring 15 mm, localized on the left lower labial mucosa, covered by healthy mucosa, with 2 years of onset. Medical history revealed fibromyalgia. With the clinical hypothesis of mesenchymal or glandular neoplasm, an incisional biopsy was performed. Histopathologic analysis revealed deposition of a hyaline, acellular, eosinophilic, and amorphous material on the connective tissue. Congo red staining was positive, with apple-green birefringence under polarized light, resulting in the diagnosis of amyloidosis. After medical evaluation, no amyloid deposits were found in other tissues and the condition was classified as cutaneous amyloidosis. Surgical excision of the labial lesion was done, with no signs of recurrence after four months. Amyloidosis represents a group of rare diseases characterized by extracellular deposition of insoluble amyloid fibrils. A 57-year-old female patient presented with a well-delimited, asymptomatic, submucosal fibrous nodule, measuring 15 mm, localized on the left lower labial mucosa, covered by healthy mucosa, with 2 years of onset. Medical history revealed fibromyalgia. With the clinical hypothesis of mesenchymal or glandular neoplasm, an incisional biopsy was performed. Histopathologic analysis revealed deposition of a hyaline, acellular, eosinophilic, and amorphous material on the connective tissue. Congo red staining was positive, with apple-green birefringence under polarized light, resulting in the diagnosis of amyloidosis. After medical evaluation, no amyloid deposits were found in other tissues and the condition was classified as cutaneous amyloidosis. Surgical excision of the labial lesion was done, with no signs of recurrence after four months.