A 60-year-old male presents with hives, skin flushing, and headaches. After an appropriate preliminary work-up, a bone marrow biopsy is performed. A representative section from the bone marrow biopsy is shown here. What are the granulated cells at the center of this image?
C. Mast cells
E. Adenocarcinoma cells
The granulated cells in this image are mast cells, which are identified by their abundant, metachromatic granules. This patient was diagnosed with systemic mastocytosis, a clonal disorder of mast cells and their precursors.
Mastocytosis is actually a spectrum of rare disorders, all of which are characterized by an increase in mast cells. Most patients have disease that is localized to the skin, but about 10% of patients have systemic involvement, like the patient in this case. There is a localized, cutaneous form of mastocytosis called urticaria pigmentosum that happens mostly in children and accounts for over half of all cases of mastocytosis.
Clinically, the skin lesions of mastocytosis vary in appearance. In urticaria pigmentosum, the lesions are small, round, red-brown plaques and papules. Other cases of mastocytosis show solitary pink-tan nodules that may be itchy or show blister formation. The itchiness is due to the release of mast cell granules (which contain histamine and other vasoactive substances).
In systemic mastocytosis, patients have skin lesions similar to those of urticaria pigmentosum – but there is also mast cell infiltration of the bone marrow, lymph nodes, spleen and liver. Patients often suffer itchiness and flushing triggered by certain foods, temperature changes, alcohol and certain drugs (like aspirin).
-Kristine Krafts, MD, is an Assistant Professor of Pathology at the University of Minnesota School of Medicine and School of Dentistry and the founder of the educational website Pathology Student.