Systemic mastocytosis associated with small lymphocytic lymphoma: an incidental finding in a patient with invasive gastric adenocarcinoma.

Mastocytosis comprises a heterogeneous group of disorders characterized by the abnormal growth and accumulation of mast cells in various tissues. We report an interesting case of systemic mastocytosis diagnosed incidentally in an omental lymph node in the setting of an invasive gastric adenocarcinoma. The Diff-Quick touch preparation of the lymph node revealed abundant single cells and loose aggregates of cells with round to oval nuclei and deeply basophilic granules. Monotonous proliferation of small mature lymphocytes and many eosinophils were also present in the background. No evidence of metastatic carcinoma was seen. The frozen section and permanent sections of lymph node showed partial to complete replacement of lymph node by neoplastic mast cells. We present the cytologic findings of this unique case in addition to a brief discussion of systemic mastocytosis in the setting of another malignancy.