Lymphoma: This is a common cause of diffuse thoracoabdominopelvic pathology, particularly when splenomegaly is absent. Lymphoma can involve multiple lymph node groups and organs, leading to widespread disease.

Metastatic Cancer: Various primary cancers (e.g., breast, lung, colon) can metastasize to multiple regions of the body, including the thorax, abdomen, and pelvis, without necessarily involving the spleen.
Sarcoidosis: This systemic granulomatous disease can affect multiple organs, including the lungs, lymph nodes, and abdominal organs, often without splenomegaly.
Tuberculosis: Although less common in some regions, tuberculosis can cause diffuse thoracoabdominopelvic pathology, including lymphadenopathy and organ involvement, without splenomegaly.

Histiocytosis: A group of rare diseases that can cause systemic symptoms and multi-organ involvement, including the lungs, bones, and abdominal organs. Missing this diagnosis could lead to delayed treatment and poor outcomes.
Systemic Lupus Erythematosus (SLE): An autoimmune disease that can affect multiple organs and systems, sometimes presenting with diffuse thoracoabdominopelvic pathology. SLE requires prompt recognition and treatment to prevent serious complications.
Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A vasculitis that can involve the respiratory tract, kidneys, and other organs, potentially leading to severe and life-threatening complications if not diagnosed and treated early.

Castleman Disease: A rare lymphoproliferative disorder that can cause lymphadenopathy and systemic symptoms, sometimes involving multiple regions of the body.
** Erdheim-Chester Disease**: A rare form of histiocytosis that can cause systemic symptoms, bone lesions, and multi-organ involvement, including the lungs, heart, and abdominal organs.
Langerhans Cell Histiocytosis: A rare disorder characterized by the proliferation of Langerhans cells, which can lead to multi-organ involvement, including the bones, lungs, and abdominal organs.