Clinical signs that cause suspicion of lymphoma include lymphadenopathy, hepatomegaly, splenomegaly, and chronic GI disorder such as vomiting or diarrhea.  Fine needle aspirate (FNA) of the area of interest is a good first step.  A monomorphic population of lymphocytes, especially in an area where lymphocytes do not usually reside, can be diagnostic.  Antigen receptor site rearrangement PCR (PARR) of stained or unstained cytology slides can be performed at a reference lab if additional information is needed.  PARR is helpful to identify the lymphocyte type (T or B) and confirm clonality (which supports lymphoid neoplasia when positive).  In cases where a presurgical FNA is impractical, formalin fixed biopsy can be diagnostic of lymphoma. Immunohistochemistry (to determine the lymphocyte type) or PARR (for lymphocyte type and confirmation of clonality) can be performed on the fixed tissue for additional information.