A 67-year-old male with a past medical history of primary melanoma of sole of foot. A large mass almost entirely replaces the spleen with thinned out capsule.
- Diffuse sheet of large epithelioid tumor cells. These cells are large and pleomorphic with vesicular nucleus and prominent large pink nucleoli and granular eosinophilic to clear cytoplasm.
- Some cells are binucleated and embryoid type nucleus.
- Atypical mitoses are seen.
- Large areas of necrotic tumor and haemorrhagic areas are also seen.
- Some tumor cells are heavily studded with brown melanin pigmentation.
Practical Points of Pathoclinics:
- Metastatic malignancy in spleen is commonly seen with primary tumors of lung, stomach, pancreas, liver, and colon. Metastatic melanoma of spleen is uncommon. Splenic metastasis is often seen late in course, with disseminated melanoma, even though spleen is a most vascular organ. At autopsy, spleen involvement is seen in 32–88% of patients who died of metastatic melanoma.
- Melanoma is common in the skin and mucous membranes. Melanoma can metastases throughout body and the common locations are the skin, lung, liver, brain, bone, and the gastrointestinal tract. Primary melanoma of spleen is extremely rare in humans. Even in absence of any history of primary melanoma, detailed investigation should be carried out, to search for occult melanoma.
- Common presenting features in metastatic melanoma are splenomegaly, pain and rare cases with spontaneous rupture of spleen.
- Grossly metastatic melanoma in spleen usually presents as a multiple nodule. Solitary metastasis of variable size is less common. Cut surface is fleshy with areas of necrosis. Large tumor mass may replace the spleen parenchyma. Pigmentation is not necessary in all cases.
- Immunostains are optional in cases with a known primary melanoma elsewhere in body and in presence of hallmark “melanin pigments”, both are satisfied in present case. Immunohistochemical markers like S100, HMB45, Melan-A/mart-1, MiTF, Tyrosinase, SOX-10 and vimentin are positive in melanoma. Other immunomarkers can be used for differentiation from other more common tumors from lung, gastro intestinal tract and breast.
- Metastatic melanoma (M1; Stage IV disease) have a poor prognosis and incurable disease. Aim of management is palliation through surgery, chemotherapy or radiation. Some reports mentioned about the survival benefit of complete surgical resection of isolated metastasis.
Dusseau B, Onders B, Radulescu A, Abourezk M, Leff J. Metastatic melanoma of the spleen without known primary. J Surg Case Rep. 2020 Dec 7;2020(12):rjaa456. doi: 10.1093/jscr/rjaa456. PMID: 33343861; PMCID: PMC7737005.