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What is T-cell prolymphocytic leukemia and explain in detail?
T-cell-prolymphocytic leukemia (T-PLL) is a mature T-cell leukemia with aggressive behavior and predilection for blood, bone marrow, lymph nodes, liver, spleen, and skin involvement. T-PLL is a very rare leukemia, primarily affecting adults over the age of 30. It represents 2% of all small lymphocytic leukemias in adults. Other names include T-cell chronic lymphocytic leukemia, "knobby" type of T-cell leukemia, and T-prolymphocytic leukemia/T-cell lymphocytic leukemia.

Signs and symptoms
People affected by T-cell prolymphocytic leukemia typically have systemic disease at presentation, including enlargement of the liver and spleen, widespread enlargement of the lymph nodes, and skin infiltrates.Due to the systemic nature of this disease, leukemic cells can be found in peripheral blood, lymph nodes, bone marrow, spleen, liver, and skin.  A high lymphocyte count (> 100 x 109/L) along with low amounts of red blood cells and platelets in the blood are common findings. HTLV-1 serologies are negative, and serum immunoglobins are within normal limits with no paraproteins present.

Causes
It is postulated that the originating cell line for this disease is a mature (post-thymic) T-cell.

Diagnosis
Morphology
In the peripheral blood, T-PLL consists of medium-sized lymphocytes with single nucleoli and basophilic cytoplasm with occasional blebs or projections. The nuclei are usually round to oval in shape, with occasional patients having cells with a more irregular nuclear outline that is similar to the cerebriform nuclear shape seen in Sézary syndrome. A small cell variant comprises 20% of all T-PLL cases, and the Sézary cell-like (cerebriform) variant is seen in 5% of cases.Marrow involvement is typically diffuse with morphology similar to what is observed in peripheral blood. In the spleen, the leukemic cell infiltrate both the red pulp and white pulp, and lymph node involvement is typically diffuse through the paracortex