Hidden morphological clues in deceptive bone marrow pathologies.

Bone marrow infiltration by dedifferentiated melanoma can mimic a hematologic neoplasm, with melanin-laden macrophages providing a critical diagnostic clue.

• The case involved dedifferentiated melanoma infiltrating the bone marrow in a pattern resembling a hematologic neoplasm.
• Melanin-laden macrophages were identified as a decisive morphological finding.
• The case illustrates the importance of recognizing functional cellular features such as hemophagocytosis and pigment-laden cells in the bone marrow microenvironment.
• Morphological clues in this case were described as 'subtle and often overlooked.'

Carcinocythemia revealing metastatic melanoma was identified with neoplastic cells confined to smear edges.

• Neoplastic cells were spatially restricted to the edges of the blood smear, representing an atypical localization pattern.
• This case of carcinocythemia — circulating tumor cells in peripheral blood — was the presenting manifestation of metastatic melanoma.
• The finding underscores that atypical spatial localization of tumor cells can provide decisive diagnostic information.
• This case demonstrates that morphological examination must include assessment of cell distribution across the entire smear preparation.

Anaplastic IgA multiple myeloma presented with striking cytological atypia in the bone marrow.

• The myeloma was characterized as anaplastic with IgA isotype.
• The case featured 'striking cytological atypia' as the predominant morphological finding.
• This case is included as an example of a diagnostically challenging setting where morphological assessment is essential.
• The case is presented within the context of requiring complementary immunophenotypic and molecular techniques alongside morphology.

Acute monoblastic leukemia presented with a rapidly fatal clinical course.

• The case was classified as acute monoblastic leukemia.
• The disease course was described as 'rapidly fatal.'
• This case is included as an example of an aggressive malignancy where morphological diagnosis is critical.
• The case illustrates the role of morphological assessment in identifying aggressive malignancies requiring urgent clinical action.

Myelodysplastic syndrome with SF3B1 mutation was characterized by prominent erythroblastic islands and subtle dysplasia.

• The case carried an SF3B1 mutation, a recognized molecular marker in myelodysplastic syndrome.
• Morphological features included 'prominent erythroblastic islands' and 'subtle dysplasia.'
• The case highlights bone marrow microenvironmental context — specifically the organization of erythroblastic islands — as a diagnostically relevant morphological feature.
• Subtle dysplasia in this case exemplifies findings that may be missed without a structured, contextual morphological approach.

Atypical spatial localization of tumor cells, functional features such as hemophagocytosis, and microenvironmental alterations were identified as decisive diagnostic morphological parameters across the case series.

• The paper argues that morphological assessment should extend beyond 'isolated cytologic features' to include 'spatial distribution of cells, functional behavior, and bone marrow microenvironmental context.'
• Hemophagocytosis is cited as a specific functional feature with diagnostic relevance.
• Microenvironmental alterations, including erythroblastic island prominence, are highlighted as underutilized diagnostic parameters.
• These findings are presented across five cases to demonstrate a 'structured, contextual morphological approach' as complementary to immunophenotypic and molecular techniques.