Systemic mastocytosis. Extracutaneous manifestations

Area of Science:

• Hematology
• Oncology
• Pathology

Background:

• Systemic mastocytosis (SM) is a rare disorder characterized by abnormal mast cell accumulation.
• SM can manifest with diverse clinical presentations, including urticaria pigmentosa (UP) or without apparent skin lesions.

Purpose of the Study:

• To comprehensively evaluate the clinical, radiologic, ultrastructural, and histopathologic features of systemic mastocytosis.
• To identify differences and commonalities between SM patients with and without urticaria pigmentosa.

Main Methods:

• Retrospective analysis of 14 patients diagnosed with systemic mastocytosis.
• Inclusion of clinical, radiologic, bone marrow biopsy, lymph node, spleen, and liver histopathology data.
• Mast cell morphology and staining characteristics were assessed.

Main Results:

• Bone marrow involvement was universal (13/13), showing focal (perivascular, paratrabecular) and diffuse patterns resembling myelofibrosis.
• Splenomegaly was more common in patients without UP (5/7 vs. 1/7), who were also older (median 75 vs. 44).
• Histopathology revealed mast cell infiltration in lymph nodes, spleen (with fibrosis), and liver (portal fibrosis). Mast cell morphology varied, and they stained positively for toluidine blue and chloroacetate esterase.
• Radiologic changes (osteoblastic, osteolytic) were observed in 6 patients. Two patients developed lymphoreticular tumors, and one developed a myeloproliferative disorder.

Conclusions:

• Systemic mastocytosis frequently involves bone marrow, lymph nodes, spleen, and liver, with characteristic histopathologic findings.
• Clinical presentation, particularly the presence of urticaria pigmentosa, may correlate with age and splenomegaly.
• The diverse mast cell morphology and potential for progression to aggressive hematologic neoplasms underscore the complexity of SM.