Morphological and immunophenotypic variations in malignant melanoma

Abstract

A variety of cytomorphological features, architectural patterns and stromal changes may be observed in malignant melanomas. Hence, melanomas may mimic carcinomas, sarcomas, benign stromal tumours, lymphomas, plasmacytomas and germ cell tumours. Melanomas may be composed of large pleomorphic cells, small cells, spindle cells and may contain clear, signet-ring, pseudolipoblastic, rhabdoid, plasmacytoid or balloon cells. Various inclusions and phagocytosed material may be present in their cytoplasm. Nuclei may show bi- or multi-nucleation, lobation, inclusions, grooving and angulation. Architectural variations include fasciculation, whorling, nesting, trabeculation, pseudoglandular/pseudopapillary/pseudofollicular, pseudorosetting and angiocentric patterns. Myxoid or desmoplastic changes and very rarely pseudoangiosarcomatous change, granulomatous inflammation or osteoclastic giant cell response may be seen in the stroma. The stromal blood vessels may exhibit a haemangiopericytomatous pattern, proliferation of glomeruloid blood vessels and perivascular hyalinization. Occasionally, differentiation to nonmelanocytic structures (Schwannian, fibro-/myofibroblastic, osteocartilaginous, smooth muscle, rhabdomyoblastic, ganglionic and ganglioneuroblastic) may be observed. Typically melanomas are S100 protein, NKIC3, HMB-45, Melan-A and tyrosinase positive but some melanomas may exhibit an aberrant immunophenotype and may express cytokeratins, desmin, smooth muscle actin, KP1 (CD68), CEA, EMA and VS38. Very rarely, neurofilament protein and GFAP positivity may be seen.

Potent Phagocytic Activity Discriminates Metastatic and Primary Human Malignant Melanomas: A Key Role of Ezrin

“…These markers clearly outline macrophage-like phagosomes, in which a progressive degradation of autologous nuclei does occur, strongly suggesting that a genuine phagocytosis underlies the in vivo phagocytosis we have shown in melanoma tumors. This supports a previous finding showing features of autophagocytosis in human melanomas (Banerjee and Harris, 2000). Our study definitively demonstrates that both the presence of a complete phagocytic machinery and the phagocytosis are consistent with the ability of melanoma cells to exert a macrophage-like activity.…”

“…These results clearly show that the phagocytic markers were mostly localized on vacuoles containing cells in various stages of degradation, suggesting the occurrence of a genuine phagocytosis in human melanoma cell cultures. Moreover, these data definitively demonstrate that a genuine macrophage-like phagocytic behavior underlies the frequent in vivo findings of autophagocytic figures in histopathologic specimens of human melanoma (Banerjee and Harris, 2000).…”

“…More recently, many morphologic aspects associated with phagocytosis have been identified in tumors (Banerjee and Harris, 2000), and the phagocytic-like activity of these cells has been associated with invasiveness (Coopman et al, 1998;Montcourrier et al, 1994). Moreover, other histopathologic signs of tumor malignancy, recalling an in vivo phagocytic-like behavior of tumor cells, have been described.…”

“…However, signet-ring cells can also be found in nonepithelial tumors, such as malignant lymphomas and melanomas (Tsang et al, 1992). The nature of these cells, particularly in nonepithelial tumors, is not known, but it is conceivable that an aberrant scavenging activity underlies this phenomenon (Banerjee and Harris, 2000;Kuroda et al, 1999). Altogether these reports suggest that active phagocytosis occurs in human tumor cells, but the phagocytic apparatus of tumor cells has never been defined and the mechanism(s) underlying this phenomenon have not been investigated.…”

A novel report of a primary Merkel cell carcinoma lesion in the nasal vestibule

“…It may also resemble melanoma which is often referred to as the “great mimicker” with its wide spectrum of possible histologic features 10, 11. Therefore, immunohistochemical staining is often used to make the diagnosis of MCC.…”