Plasmacytoid melanoma of the urinary bladder and lymph nodes with immunohistochemical expression of plasma cell markers revealing primary esophageal melanoma

Abstract

Plasmacytoid variant of melanoma is reported in only rare cases. We present the case of a 54-years-old man admitted for enlarged lymph nodes in the lumbar region. Initial diagnosis of plasmablastic lymphoma/plasma cell myeloma was considered. At our institute, a bladder polyp was removed. Microscopic exam demonstrated dense plasmacytoid cells infiltration with pigment deposits. Immunohistochemical study showed strong expression of HMB45, Melan A, and vimentin. There was focal positivity with S100 protein and CD138/syndecan-1. The diagnosis of metastatic plasmacytoid melanoma was finally established. Clinical exam revealed an esophageal melanoma with melanosis supporting its primary location. Although rarely, melanoma especially plasmacytoid variant may express plasma cell markers which may lead to erroneous diagnosis of plasma cell proliferation. Careful morphological examination for melanin pigment and the use of panel of melanocytic markers are helpful for diagnosis.

Figure 1

Diffuse proliferation of rounded neoplastic cells showing incohesion (HE ×40).

Figure 2

neoplastic cells demonstrated eosinophilic cytoplasm and eccentric nuclei with prominent nucleoli; some cells are binucleated (⇒); note the presence of pigment (⊷) (HE ×400).

Figure 3

(a) Neoplastic cells exhibit immunoreactivity for CD138 (×100). (b) Very rare neoplastic cells are positive for S100 protein (×100). (c) Strong HMB45 expression by the neoplastic cells (×40). (d) Neoplastic cells are positive for lambda light chain and negative for kappa light chain (×100).

Figure 4

Esophageal tumor containing a mixture of epitheliod and spindle-shaped cells (HE ×40).

Figure 5

Esophageal tumor—sheets of large cells with plasmacytoid features (HE ×400).

Figure 6

(a) Neoplastic cells showed strong positivity with S100 protein (×100). (b) Focal expression for CD138/syndecan-1 (×100). (c) Neoplastic cells showed strong positivity with HMB45 (×40). (d) HMB45 staining showing increased number of melanocytic cells at the basal layer of the squamous epithelium (×100).