Skin nodules and back pain.

QUESTION: A 50-year-old man who had recently completed consolidation chemotherapy for acute myelocytic leukemia presented with lower back pain radiating to his right leg. He did not have bowel or bladder incontinence. The patient also reported the growth of multiple greenish skin nodules a few weeks before presentation (figure 1). A bone marrow biopsy had been negative for leukemic cells 1 month before presentation. Figure 1 Skin nodule, 12 mm in diameter On physical examination, the patient had a normal gait and sensation but a decreased ankle reflex, and the straight leg raising test was positive on the right side. Several 1- to 2-cm nontender greenish nodules were present on his trunk and thighs. What is the origin of this patient's skin condition, and how does it relate to his lower back pain? ANSWER: This patient has chloromas (granulocytic sarcomas) of his skin and meninges, the latter causing spinal nerve root compression. A chloroma is defined as a green tumor consisting of leukemic cells, with the combining form of the word, “chloro-” being derived from Greek for green (as in chlorophyll). The green color is most noticeable surrounding the red papule on the skin in figure 1. Magnetic resonance imaging of the spine (figure 2) showed diffuse leukemic infiltration throughout his spine, causing compression of his cauda equina, and a subsequent lumbar puncture revealed lymphoblastic cells. A biopsy of the patient's skin nodules confirmed the presence of leukemic cells (figure 3). Figure 2 Spinal magnetic resonance image showing cauda equina compression (arrow) Figure 3 Skin biopsy showing an infiltrate of leukemic cells Chloromas are a rare manifestation of both acute myelogenous and acute lymphocytic leukemia. They usually are seen in younger patients with leukemia and have been described in almost every anatomic location. In most cases, the tumor is associated with coexisting acute leukemia; in fact, it may herald a hematologic relapse, as in this patient.1 Histologically, a chloroma is composed of sheets of primitive cells of the myeloid or monoblastoid type. The greenish tint of the tumor is due to myeloperoxidase found in the neutrophilic leukocytes. The conditions most likely to be confused with chloroma (if the diagnosis of leukemia has not already been made) are histiocytic lymphoma and eosinophilic granuloma.2 Chloromas rarely cause spinal cord compression.3 Most cases of acute cauda equina syndrome are caused by mechanical compression of spinal nerve roots by either tumor or infection. The most common neoplastic causes of spinal cord compression include prostate, breast, and lung cancer. The treatment of cauda equina syndrome requires urgent decompression of the involved nerve roots, with radiation therapy, the administration of steroids, chemotherapy, or surgery.4 The patient underwent urgent total spine irradiation, which resulted in rapid lessening of his lower back pain. He then declined further chemotherapy, opting instead for palliative care.