A "dry tap" refers to a bone marrow aspirate ("tap") that yields no material ("dry"). A trephine biopsy may be needed in these situations to obtain diagnostic material.
Mechanisms of a dry tap in a properly performed bone marrow aspirate:
(1) patchy or diffuse fibrosis
(2) hypercellularity and/or more adherent cells
Conditions associated with a dry tap include:
(1) asplastic anemia
(3) other myeloproliferative disorders
(4) acute leukemia, including hairy cell leukemia
(5) malignant non-Hodgkin's lymphoma or Hodgkin's disease
(7) metastatic carcinoma, especially with sclerosis
(8) technical error (failure to enter medullary space), which may be related to inexperience or patient movement
If a dry tap is encountered, it is important to examine all of the material retrieved. Although this material may only consist of blood clot, it may contain enough cells in the case of metastatic carcinoma to make the diagnosis.
In osteosclerosis it may be extremely difficult to introduce the needle.
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Specialty: Hematology Oncology, Clinical Laboratory