Background and Objective:Amyloid deposition is rare.If there was a great amount of amyloid depositions in the skin tissue,it would be considered to be amyloid deposition disease at first,and then primary cutaneous marginal zone B-cell lymphoma(PCMZL).This study was to analyze the diagnosis and differential diagnosis of two cases of PCMZL with amyloid deposition.Methods:Clinicopathologic characteristics and follow-up of two cases of PCMZL were analyzed.Immunohistochemical staining was performed by EnVision method using antibodies LCA,CD19,CD20,CD79a,CD3,CD7,MUM1,κ,λ,Ki-67.IgH and TCRγ gene rearrangement was detected by polymerase chain reactive(PCR).Results:Case 1,a 71-year-old Chinese male,had a subcutaneous mass on the right elbow that was initially diagnosed with “amyloidosis” in 2004.Three years after the initial diagnosis,he developed recurrences on the right para-auxillary that was still diagnosed with “probably amyloidosis”.Four years after the first diagnosis,the patient presented a lesion on the right para-auxillary with a diameter of 2 cm and a lesion on the temporal-parietal dural with a size of 6.0 cm × 3.0 cm × 3.0 cm.Case 2,a 68-year-old Chinese male,had a subcutaneous mass next to back of the left ear with a size of 9.0 cm × 5.0 cm,and he underwent a operation one year previously because of subcutaneous mass in the same site.Microscopically,the tumors of both cases were located in dermis and subcutaneous,tumor cells were medium size with a nodular or diffuse distribution,and some of tumor cells were plasmacytoid/plasma cells.Morphologically,the temporal-parietal dural lesion was similar to subcutaneous lesion and infiltrated into cranial(case 1).Juxtaposed the tumor cells of two cases,there were the large amyloid deposits of amorphous hyaline material and concentrically laminated hyaline spherules in case 1,while cord-like amyloid deposits in case 2.Reactive lymphoid follicles with germinal centers and foreign body giant cells in the stroma were found surrounding the amyloid deposits.Congo red staining showed positive of amyloid deposition in tumor tissues of both cases.Immunohistochemical staining revealed that LCA,CD19,CD20,CD79a and MUM1 expressions were positive in tumor cells,and Ki-67 expression was about 8%-10%.IgL restricted expression as κ positive while λ negative was found in both cases.PCR results showed monoclone gene rearrangement of IgH gene in both cases.Conclusions:Our findings suggest that amyloid deposition rarely present in both primary and metastatic tumors in PCMZL,and its diagnosis should be considered to avoid misdiagnosis.The patients with PCMZL should undergo regular examinations and chemotherapy as well as a long-term follow-up since it is apt to recur or relapse. Background and Objective: Amyloid deposition is rare. It has a great amount of amyloid depositions in the skin tissue, it would be considered to be amyloid deposition disease at first, and then primary cutaneous marginal zone B-cell lymphoma (PCMZL) .This study was to analyze the diagnosis and differential diagnosis of two cases of PCMZL with amyloid deposition. Methods: Clinicopathologic characteristics and follow-up of two cases of PCMZL were analyzed. Immunohistochemical staining was performed by EnVision method using antibodies LCA, CD19, CD20, CD79a , CD3, CD7, MUM1, κ, λ, Ki-67. IgH and TCRγ gene rearrangement was detected by polymerase chain reactive (PCR). Results: Case 1, a 71-year-old Chinese male, had a subcutaneous mass on the right elbow that was initially diagnosed with “amyloidosis ” in 2004.Three years after the initial diagnosis, he advanced recurrences on the right para-auxillary that was still diagnosed with “probably amyloidosis ”. Four years after the first diagnosis, the patient presented a lesion on the right para-auxillary with a diameter of 2 cm and a lesion on the temporal-parietal dural with a size of 6.0 cm × 3.0 cm × 3.0 cm. Case 2, a 68-year-old Chinese male, had a subcutaneous mass next to back of the left ear with a size of 9.0 cm × 5.0 cm, and he underwent a operation one year because because of the subcutaneous mass in the same site. Microscopically, the tumors of both cases were located in dermis and subcutaneous , tumor cells were medium size with a nodular or diffuse distribution, and some of the tumor cells were plasmacytoid / plasma cells. Morphologically, the temporal-parietal dural lesion was similar to subcutaneous lesion and infiltrated into cranial (case 1). Juxtaposed the tumor cells of two cases, there were the large amyloid deposits of amorphous hyaline material and concentrically laminated hyaline spherules in case 1, while cord-like amyloid deposits in case 2. Reactive lymphoid follicles with germinal centers and foreign body giant cells in the stroma w ere foundulating surrounding amyloid deposits. Cito red staining showed positive of amyloid deposition in tumor tissues of both cases. Immunohistochemical staining revealed that LCA, CD19, CD20, CD79a and MUM1 expressions were positive in tumor cells, and Ki- 67 expression was about 8% -10% .IgL restricted expression as κ positive while λ negative was found in both cases. PCR results showed monoclone gene rearrangement of IgH gene in both cases. Conclusions: Our findings suggest that amyloid deposition rarely present in both primary and metastatic tumors in PCMZL , and its diagnosis should be considered to avoid misdiagnosis.The patients with PCMZL should undergo regular examinations and chemotherapy as well as a long-term follow-up since it is apt to recur or relapse.